User manual | STMPE321 3-channel capacitive touchkey controller Features

STMPE321
3-channel capacitive touchkey controller
Features
■
Up to 3 GPIOs
■
Up to 3 capacitive touchkey inputs
■
Operating voltage 1.65 - 1.95 V
■
Interrupt output pin
■
I2C interface (1.8 V operation, 3.3 V tolerant)
■
8 kV HBM ESD protection
■
40 fF resolution, 128-step capacitance
measurement
QFN12
(2.2 x 1.5 mm)
■
Advanced data filtering (AFS)
■
Environment tracking calibration (ETC)
■
Individually adjustable touch variance (TVR)
settings for all channels
■
Adjustable environmental variance (EVR) for
optimal calibration
■
Capacitive key sensing capability in 27 µA
sleep mode
Applications
■
Mobile phones and smartphones
■
Portable media players
■
Game consoles
Table 1.
Description
The STMPE321 is a 3-channel capacitive
touchkey controller. Capacitance measurement is
implemented in fully optimized hardware.
All 3 I/Os can be configured via an I2C bus to
function as either capacitive touchkey, or as
GPIOs (general purpose I/O).
Device summary
Order code
Package
Packing
STMPE321QTR
QFN12 (2.2 x 1.5 mm)
Tape and reel
August 2009
Doc ID 15791 Rev 3
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www.st.com
40
Contents
STMPE321
Contents
1
2
STMPE321 functional overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1
STMPE321 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2
Pin assignment and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3
STMPE321 typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Capacitance compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1
2.2
Calibration algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1
Noise filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.2
Data filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Power management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3
I2C interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4
Register map and function description . . . . . . . . . . . . . . . . . . . . . . . . . 12
5
System and identification registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6
Interrupt controller module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7
GPIO controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8
Capacitive touch module registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9
Maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
10.1
Capacitive sensing characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
11
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
12
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
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Doc ID 15791 Rev 3
STMPE321
1
STMPE321 functional overview
STMPE321 functional overview
The STMPE321 consists of the following blocks:
1.1
●
GPIO controller
●
Impedance sensor
●
Touchkey controller
●
I2C interface
STMPE321 block diagram
Figure 1.
Functional block diagram
IO
controller
Touch 0-2
GPIO 0-2
Impedance
sensor
RST
SCLK
SDA
Host
interface
Touchkey
controller
INT
GND
ARef
VCC
!-6
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STMPE321 functional overview
1.2
STMPE321
Pin assignment and function
Figure 2.
QFN12 pin assignment (top view)
!-
Table 2.
4/40
Pin assignment and function
Pin number
Pin name
Description
1
GPIO_2 / touch 2
GPIO 2
2
GPIO_1 / touch 1
GPIO 1
3
GPIO_0 / touch 0
GPIO 0
4
NC
-
5
SDA
I2C data
6
SCL
I2C clock
7
GND
GND
8
VCC
Supply voltage
9
ARef
Reference capacitor for touch sensor
10
NC
-
11
INT
INT output (open drain)
12
RST
RESET (active low)
This pin is internally pulled up to VCC
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STMPE321
1.3
STMPE321 functional overview
STMPE321 typical application
The STMPE321 is capable of supporting capacitive sensors of up to 3 channels.
Figure 3.
Typical application diagram
34-0%
4OUCH
3#,+
3$!4
4OUCH
4OUCH
3ENSORPADS
"ASEBAND#05
234
).4
!2EF
3ENSORPADSARETYPICALLY MM Doc ID 15791 Rev 3
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Capacitance compensation
2
STMPE321
Capacitance compensation
The STMPE321 is capable to measuring up to 5.1pF in capacitance difference between the
reference point (Zref) and the individual channels. In the case where PCB connection
between the sensor pads and the device is too long, the "REFERENCE DELAY" register is
able to shift the reference by up to 5.1pF, allowing the TOUCH channels to measure added
capacitance 5.1pF with offset of 5.1pF, as shown in following diagram.
In the case where this is still not enough to compensate for the capacitance on sensor lines
(due to very long sensor trace), an external capacitor of up to 30 pF could be connected at
the A_Ref pin.
This would further shift up the dynamic range of the capacitance measurement.
Figure 4.
Capacitance compensation
P&
P&
2EFERENCEDELAYREGISTER
$YNAMICRANGEP&
P&
2EFERENCEDELAYREGISTERP&
$YNAMICRANGEP&
P&
P&
P&
2EFERENCEDELAYP&
!2EFP&
$YNAMICRANGEP&P&
)NCREASINGCAPACITANCE
!-6
The sensed capacitance is accessible to the host through the IMPEDANCE registers.
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STMPE321
2.1
Capacitance compensation
Calibration algorithm
The STMPE321 maintains 2 parameters for each touch channel: TVR and CALIBRATED
IMPEDANCE. CALIBRATED IMPEDANCE is an internal reference which, if the currently
measured IMPEDANCE exceeds the CALIBRATED IMPEDANCE by a magnitude of TVR, is
considered a “TOUCH”.
If the IMPEDANCE is higher than the CALIBRATED IMPEDANCE, but the magnitude does
not exceed CALIBRATED IMPEDANCE by TVR, it is not considered a TOUCH. In this case,
2 scenarios are possible:
1. Environmental changes have caused the IMPEDANCE to increase
2. Finger is near the sensing pad, but not near enough
In case 1, the change in IMPEDANCE is expected to be small, as environmental changes
are normally gradual. A value "EVR" is maintained to specify the maximum IMPEDANCE
change that is still considered an environmental change.
Table 3.
Calibration action under different scenarios
Scenario
Touch sensing and calibration action
IMP>CALIBRATED IMP + TVR
TOUCH,
no calibration
IMP<CALIBRATED IMP + TVR
IMP>CALIBRATED IMP + EVR
NO TOUCH,
no calibration
IMP<CALIBRATED IMP + TVR
IMP<CALIBRATED IMP + EVR
IMP>CALIBRATED IMP
NO TOUCH,
new CALIBRATED IMP = previous CALIBRATED
IMP + change in IMP
IMP>CALIBRATED IMP
CALIBRATED IMP + change in IMP
IMP<CALIBRATED IMP
NO TOUCH,
new CALIBRATED IMP = new IMP
‘IMP’ and ‘CALIBRATED IMP’ used in this table is not the direct register read-out.
IMP = 127 - impedance register readout
CALIBRATED IMP = 127 - calibrated impedance register readout.
The ETC WAIT register states a period of time for which all TOUCH inputs must remain "NO
TOUCH" for the next calibration to be carried out.
The CAL INTERVAL states the period of time between successive calibrations when there
are prolonged NO TOUCH conditions.
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Capacitance compensation
2.1.1
STMPE321
Noise filtering
When the STMPE321 is operating in the vicinity of highly emissive circuits (DC-DC
converters, PWM controllers/drives etc.), the sensor inputs can be affected by highfrequency noise. In this situation, the time-integrating function can be used to distinguish
between a real touch, or an emission-related false touch.
The INTEGRATION TIME and STRENGTH THRES registers are used to configure the timeintegrating function of the STMPE321.
2.1.2
Data filtering
The output from the calibration unit provides an instantaneous TOUCH or NO TOUCH
status. This output is directed to the filtering stage where the TOUCH is integrated across a
programmable period of time. The output of the integration stage is a “STRENGTH" (in the
STRENGTH register) that indicates the number of times a TOUCH is detected across the
integration period.
The STRENGTH is then compared to the value in STRENGTH THRESHOLD register. If
STRENGTH exceeds the STRENGTH THRESHOLD, it is considered a final, filtered
TOUCH status.
In the data filtering stage, 3 modes of operation are supported:
Mode 1: Only the touch channel with highest STRENGTH is taken
Mode 2: All touch channels with STRENGTH > STRENGTH THRESHOLD are taken
Mode 3: The 2 touch channels with the highest STRENGTH are taken.
These modes are selected using the FEATURE SELECTOR register. The final, filtered data
is accessible through the Touch Byte register.
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STMPE321
2.2
Capacitance compensation
Power management
The STMPE321 operates in 3 states, as described below:
Figure 5.
STMPE321 operating states
2%3%4 !#4)6%
-(Z
(OSTCOMMAND (OSTCOMMAND
(OTKEY
4OUCHHOTKEY
INTERRUPTAND
HOSTCOMMAND
(OSTCOMMAND
3,%%0 +(Z
()"%2.!4%
!-6
On RESET, the STMPE321 enters the ACTIVE state immediately.
Upon a fixed period of inactivity, the device enters a SLEEP state. Any touch activity
occurring during a SLEEP state causes the device to return to an ACTIVE state.
In SLEEP mode:
-Calibration continues if the F2A bit is set in the CONTROL register
-Calibration stops if the F2A bit is NOT set in the CONTROL register
If no touch activity is expected, the host may set the device to a HIBERNATE state to save
power.
If any key is touched and held, the I2C command to enter SLEEP or HIBERNATE is put on
hold until the key is released.
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I2C interface
3
STMPE321
I2C interface
The following features are supported by the I2C interface:
●
I2C slave device
●
Compliance with Philips I2C specification version 2.1
●
Standard (up to 100 kbps) and fast (up to 400 kbps) modes.
●
7-bit and 10-bit device addressing modes
●
General call
●
Start/Restart/Stop
●
I2C address is 0x58 (0xB0/0xB1 for write/read, including the LSB)
Start condition
A Start condition is identified by a falling edge of SDATA while SCLK is stable at high state.
A Start condition must precede any data/command transfer. The device continuously
monitors for a Start condition and does not respond to any transaction unless one is
encountered.
Stop condition
A Stop condition is identified by a rising edge of SDATA while SCLK is stable at high state.
A Stop condition terminates communication between the slave device and bus master. A
read command that is followed by NoAck can be followed by a Stop condition to force the
slave device into idle mode. When the slave device is in idle mode, it is ready to receive the
next I2C transaction. A Stop condition at the end of a write command stops the write
operation to the registers.
Acknowledge bit (ACK)
The acknowledge bit is used to indicate a successful byte transfer. The bus transmitter
releases the SDATA after sending eight bits of data. During the ninth bit, the receiver pulls
the SDATA low to acknowledge the receipt of the eight bits of data. The receiver may leave
the SDATA in high state if it does not acknowledge the receipt of the data.
Data Input
The device samples the data input on SDATA on the rising edge of the SCLK. The SDATA
signal must be stable during the rising edge of SCLK and the SDATA signal must change
only when SCLK is driven low.
Memory addressing
For the bus master to communicate to the slave device, the bus master must initiate a Start
condition, followed by the slave device address. Accompanying the slave device address,
there is a Read/WRITE bit (R/W). The bit is set to 1 for a read operation, and 0 for a write
operation.
If a match occurs on the slave device address, the corresponding device gives an
acknowledgement on the SDA during the 9th bit time. If there is no match, it deselects itself
from the bus by not responding to the transaction.
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STMPE321
I2C interface
Table 4.
Operation modes
Mode
Byte
Programming sequence
Start, Device address, R/W = 0, Register address to be read
Restart, Device address, R/W = 1, Data Read, STOP
If no Stop is issued, the Data Read can be continuously performed. If
the register address falls within the range that allows an address autoincrement, then the register address auto-increments internally after
every byte of data being read. For those register addresses that fall
within a non-incremental address range, the address is kept static
throughout the entire write operations. Refer to the memory map table
for the address ranges that are auto and non-increment. An example
of such a non-increment address is FIFO.
≥1
Read
Start, Device address, R/W = 0, Register address to be written, Data
Write, Stop
≥1
Write
Stop
Data
Read + 2
No Ack
Data
Read + 1
Ack
Stop
No Ack
Data
Read
Ack
Ack
R/W=1
Ack
R/W=1
Data to
Write + 2
Ack
Stop
Data to
Write + 1
Ack
Data to
Write
Ack
Data
to be
written
Data
Read
Ack
Stop
Ack
Restart
Ack
Restart
Reg
Address
Device
Address
Ack
Reg
Address
Device
Address
Ack
Ack
R/W=0
Ack
R/W=0
R/W=0
Device
Address
Reg
Address
Ack
Device
Address
Reg
Address
Ack
Device
Address
R/W=0
More than one byte
Read
Start
One byte
Write
Start
More than one byte
Read
Device
Address
Start
One byte
Read
Read and write modes (random and sequential)
Start
Figure 6.
If no Stop is issued, the Data Write can be continuously performed. If
the register address falls within the range that allows address autoincrement, then the register address auto-increments internally after
every byte of data being written in. For those register addresses that
fall within a non-incremental address range, the address is kept static
throughout the entire write operations. Refer to the memory map table
for the address ranges that are auto and non-increment.
Master
Slave
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Register map and function description
4
STMPE321
Register map and function description
This section lists and describes the registers in the STMPE321 device starting with a
register map, and then provides detailed descriptions of the register types.
Table 5.
Register summary map table
Address
Register name
Bit
Type
Reset value
Function
0x00
CHIP_ID_0
8
R
0x03
Device identification
0x01
CHIP_ID_1
8
R
0x21
Device identification
0x02
ID_VER
8
R
0x03
Revision number
0x03
SYS_CFG_1
8
R/W
0x00
System configuration 1
0x04
SYS_CFG_2
8
R/W
0xEF
System configuration 2
0x08
INT_CTRL
8
R/W
0x01
Interrupt control register
0x09
INT_EN
8
R/W
0x01
Interrupt enable register
0x0A
INT_STA
8
R
0x09
Interrupt status register
0x0B
GPIO_INT_EN_lsb
8
R/W
0x00
GPIO interrupt enable register
0x0C
GPIO_INT_EN_msb
8
R/W
0x00
GPIO interrupt enable register
0x0D
GPIO_INT_STA_lsb
8
R/W
0x00
GPIO interrupt status register
0x0E
GPIO_INT_STA_msb
8
R/W
0x00
GPIO interrupt status register
0x10
GPIO_MR
8
R/W
0x00
GPIO monitor pin
0x12
GPIO_SET
8
R/W
0x00
GPIO set pin state register
0x14
GPIO_DIR
8
R/W
0x00
GPIO set pin direction register
0x16
GPIO_FUNCT
8
R/W
0x00
GPIO function register
0x18
TOUCH_FIFO
64
R
0x00
Fifo access for touch data buffer
0x20
FEATURE_SEL
8
R/W
0x04
Feature selection
0x21
ETC_WAIT
8
R/W
0x27
Wait time
0x22
CAL_INTERVAL
8
R/W
0x30
Calibration interval
0x23
INTEGRATION_ TIME
8
R/W
0x0F
Integration time
0x25
CTRL
8
R/W
0x00
Control
0x26
INT_MASK
8
R/W
0x08
Interrupt mask
0x27
INT_CLR
8
R/W
0x00
Interrupt clear
0x28
FILTER_PERIOD
8
R/W
0x00
Filter period
0x29
FILTER_THRESHOLD
8
R/W
0x00
Filter threshold
0x2A
REF_DLY
8
R/W
0x00
Reference delay
0x30 0x32
TVR [0-2]
8
R/W
0x08
Touch variance setting
EVR
8
R/W
0x04
Environmental variance
0x40
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STMPE321
Table 5.
Address
Register map and function description
Register summary map table (continued)
Bit
Type
Reset value
Function
STRENGTH_THRES
[0-2]
8
R/W
0x01
Setting of strength threshold for each
channel
0x60 0x62
STRENGTH [0-2]
8
R
0x00
Strength
0x70 0x72
CAL_IMPEDANCE [0-2]
8
R
0x00
Calibrated impedance
0x80 0x82
IMPEDANCE [0-2]
8
R
0x00
Impedance
INT_PENDING
8
R/W
0x00
Status of GINT interrupt sources
0x50-0x52
0x92
Register name
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System and identification registers
STMPE321
5
System and identification registers
Table 6.
System and identification registers map
Address
Register name
Bit
Type
Reset
0x00
CHIP_ID_0
8
R
0x03
Device
identification
0x01
CHIP_ID_1
8
R
0x21
Device
identification
0x02
ID_VER
8
R
0x03
Revision number
0x03
SYS_CFG_1
8
R/W
0x00
System
configuration 1
0x04
SYS_CFG_2
8
R/W
0xEF
System
configuration 2
CHIP_ID_x
Device identification
Address:
0x00, 0x01
Type:
R
Reset:
0x03, 0x21
Description:
16(8+8)-bit device identification
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Function
Doc ID 15791 Rev 3
STMPE321
System and identification registers
ID_VER
Revision number
Address:
0x02
Type:
R
Reset:
0x03
Description:
8-bit revision number
SYS_CFG_1
7
System configuration 1
6
5
RESERVED
4
3
2
1
0
SLEEP
WARM_RESET
SOFT_RESET
HIBERNATE
Address:
0x03
Type:
R/W
Reset:
0x00
Description:
The reset control register enables the reset of the device
[7:4] RESERVED
[3] SLEEP:
Write ‘1’ to enable sleep mode. Hardware resets this bit to ‘0’ after it successfully enters sleep
mode.
[2] WARM_RESET:
Write ‘1’ to initiate a warm reset. Register content remains, state machine reset.
[1] SOFT_RESET:
Write ‘1’ to initiate a soft reset. All registers content and state machines reset.
[0] HIBERNATE: Force the device into hibernation mode.
Write ‘1’ to enter hibernate mode. Hardware resets this bit to ‘0’ after it successfully enters
hibernate mode.
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System and identification registers
STMPE321
SYS_CFG_2
System configuration 2
7
6
5
SENSOR
CLOCK 2
SENSOR
CLOCK 1
SENSOR
CLOCK 0
4
3
RESERVED
2
1
0
GPIO CLOCK
DISABLE
FIFO CLOCK
DISABLE
TOUCH CLOCK
DISABLE
Address:
0x04
Type:
R/W
Reset:
0xEF
Description:
This register enables the switching off of the clock supply
[7:5] SENSOR CLOCK: See description in Table 7.
[4] RESERVED
[3] RESERVED
[2] GPIO CLOCK DISABLE:
Write ‘1’ to disable the clock to GPIO unit.
[1] FIFO CLOCK DISABLE:
Write ‘1’ to disable the clock to FIFO unit. This must be set to ‘0’ if touch interrupt is required.
[0] TOUCH CLOCK DISABLE:
Write ‘1’ to disable the clock to TOUCH unit.
Table 7.
Mode
Operational
(6.5 MHz)
Autosleep
(200 kHz)
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Sensor clock setting
Divider
Sensor clock
[2:0]
Active
Calibration
1
000
12.8 kHz
100 kHz
2
001
6.4 kHz
50 kHz
4
010
3.2 kHz
25 kHz
8
011
1.6 kHz
12.5 kHz
16
1xx
800 Hz
6.25 kHz
1
000
400 Hz
3.2 kHz
2
001
200 Hz
1.6 kHz
4
010
100 Hz
800 Hz
8
011
50 Hz
400 Hz
16
1xx
25 Hz
200 Hz
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STMPE321
6
Interrupt controller module
Interrupt controller module
Figure 7.
Interrupt controller module block diagram
Interrupt
status
INT
pending
INT
AND
Interrupt
enable
INT MASK
GPIO
interrupt
status
AND
GPIO
interrupt
enable
!-6
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Interrupt controller module
STMPE321
INT_CTRL
7
Interrupt control register
6
5
4
3
RESERVED
2
1
0
POLARITY
TYPE
INT_EN
Address:
0x08
Type:
R/W
Reset:
0x01
Description:
This register is used to enable control of the polarity, edge/level and enabling of the
interrupt system device.
[7:3] RESERVED
[2] POLARITY:
'0' for active low
'1' for active high
For active low operation, the INT pin should be externally pulled high. The INT pin is pulled to
GND when there is a pending interrupt.
For active high operation, the INT pin should be externally pulled to GND. In this mode, the INT
pin is pulled to VCC by the device when there is a pending interrupt.
[1] TYPE:
'0' for level trigger
'1' for edge trigger (pulse width is 200 nS)
[0] INT_EN:
'0' to disable all interrupts
'1' to enable all interrupts
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STMPE321
Interrupt controller module
INT_EN
7
Interrupt enable register
6
5
GPIO
4
3
RESERVED
2
1
0
GEN
FIFO
POR
Address:
0x09
Type:
R/W
Reset:
0x01
Description:
This register is used to enable the interruption from a system related interrupt source
to the host. Writing ‘1’ in this register enables the corresponding interrupt event to
generate interrupt signal at the INT pin. Note that even if the interrupt is not enabled,
an interrupt event is still reflected in the interrupt status register.
[7] GPIO:
One or more level transition in enabled GPIOs
[6:3] RESERVED
Must be set to ‘0’ at all times.
[2] GEN:
System INT (A2I, I2A, EOC)
[1] FIFO:
Data available in FIFO. This interrupt can be cleared only if FIFO is empty.
[0] POR:
Power-on reset
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Interrupt controller module
STMPE321
INT_STA
7
Interrupt status register
6
5
GPIO
4
3
RESERVED
2
1
0
GEN
FIFO
POR
Address:
0x0A
Type:
R/W
Reset:
0x09
Description:
This register is used to enable the interruption from a system related interrupt source
to the host. Regardless of whether or not the IESYSIOR bits are enabled, the
ISSYSIOR bits are still updated. Writing ‘1’ clears a bit in this register. Writing ‘0’ has
no effect.
[7] GPIO:
One or more level transition in enabled GPIOs
[6:3] RESERVED:
Some of these bits might be set to '1' by hardware during normal operation. The content of
these bit is for internal operation and are not required for normal use of device.
[2] GEN:
System INT (A2I, IA2, EOC)
[1] FIFO:
Data available in FIFO
[0] POR:
Power-on reset
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STMPE321
Interrupt controller module
GPIO_INT_EN
7
GPIO interrupt enable registerI
6
5
4
3
2
1
RESERVED
0
IEG
Address:
0x0B, 0x0C
Type:
R/W
Reset:
0x00
Description:
The GPIO interrupt enable register is used to enable the interruption from a particular
GPIO interrupt source to the host. The IEg[2:0] bits and the interrupt enable mask bits
correspond to the GPIO[2:0] pins.
[7:3] RESERVED
[2:0] IEG[2:0]
Interrupt enable GPIO mask (where x = 2 to 0)
Writing a ‘1’ to the IE[x] bit enables the interruption to the host.
GPIO_INT_STA
7
6
GPIO interrupt status register
5
4
3
2
1
0
ISG
Address:
0x0D, 0x0E
Type:
R/W
Reset:
0x00
Description:
The GPIO interrupt status register LSB monitors the status of the interruption from a
particular GPIO pin interrupt source to the host. Regardless of whether or not the
IEGPIOR bits are enabled, the INT_STA_GPIO_LSB bits are still updated. The
ISG[2:0] bits are the interrupt status bits correspond to the GPIO[2:0] pins.
[7:0] ISG[x]:
Interrupt status GPIO (where x = 2 to 0)
Read:
Interrupt status of the GPIO[x]. Writing ‘1’ clears a bit. Writing ‘0’ has no effect.
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GPIO controller
7
STMPE321
GPIO controller
A total of 3 GPIOs are available in the STMPE321. The GPIO controller contains the
registers that allow the host system to configure each of the pins into either a GPIO or Touch
input. Unused GPIOs should be configured as outputs to minimize power consumption.
A group of registers is used to control the exact function of each of the 3 GPIOs. The
registers and their respective addresses are listed in Table 8.
Table 8.
GPIO controller registers summary map
Address
Register name
Description
Auto-increment
0x10
GPIO_MR_LSB
GPIO_MR_MSB
GPIO monitor pin state
register
Yes
0x11
0x12
GPIO_SET_LSB
Yes
0x13
GPIO_SET_MSB
GPIO set pin state
register
0x14
GPIO_DIR_LSB
GPIO_DIR_MSB
GPIO set pin direction
register
Yes
0x15
0x16
GPIO_FUNCT_LSB
GPIO function register
Yes
0x17
GPIO_FUNCT_MSB
All GPIO registers are named GPxx, where:
Xxx represents the functional group
For LSB registers:
7
6
5
4
3
RESERVED
2
1
0
IO-2
IO-1
IO-0
2
1
0
For MSB registers:
7
6
5
4
3
RESERVED
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STMPE321
GPIO controller
The function of each bit is shown inTable 9:
Table 9.
GPIO control bits function
Register name
Function
GPIO monitor pin state
Reading this bit yields the current state of the bit. Writing has no
effect.
GPIO set pin state
Writing '1' to this bit causes the corresponding GPIO to go to '1' state
Writing '0' to this bit causes the corresponding GPIO to go to '0' state
GPIO set pin direction
'0' sets the corresponding GPIO to input state, and '1' sets it to output
state. All bits are '0' on reset.
GPIO function
'1' sets the corresponding GPIO to function as GPIO, and '0' sets it to
touchkey mode.
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Capacitive touch module registers
8
STMPE321
Capacitive touch module registers
Table 10.
TOUCH_FIFO summary table
Address
Function
0x18
FIFO-0, LSB
0x19
FIFO-0, MSB
0x1A
FIFO-1, LSB
0x1B
FIFO-1, MSB
0x1C
FIFO-2, LSB
0x1D
FIFO-2, MSB
0x1E
FIFO-3, LSB
0x1F
FIFO-3, MSB
TOUCH_FIFO
Touch FIFO
7
6
5
4
3
2
1
0
T7
T6
T5
T4
T3
T2
T1
T0
Address:
0x19, 0x18
Type:
R
Reset:
0x00
Description:
TOUCH_FIFO is the access port for the internal 4-level FIFO used for buffering the
touch events. While it is possible to access each byte in the data structure directly, it is
recommended that the FIFO is accessed only via the 0x18 address.
The FIFO must be accessed in multiples of 2 bytes (LSB, MSB). For the STMPE321,
MSB is reserved and LSB contains a snapshot of the recent touch event.
Where Tn is touch status of touch sensing channel n.
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STMPE321
Capacitive touch module registers
FEATURE_SELECT
7
6
Feature select
5
4
3
2
RESERVED
1
0
AFS[1:0]
Filter EN
Address:
0x20
Type:
R/W
Reset:
0x04
Description:
Controls AFS (advanced filtering system and second level filtering feature)
[7:3] RESERVED
[2:1] AFS[1:0]:
“00’: reserved
“01’ AFS mode 1 (only 1 strongest key)
‘10’: AFS mode 2 (all keys that are above threshold)
‘11’: AFS mode 3 (the 2 strongest keys)
[0] Filter EN:
Write '1' to enable filter
ETC_WAIT
7
Wait time setting
6
5
4
3
2
1
0
ETC_WAIT[7:0]
Address:
0x21
Type:
R/W
Reset:
0x27
Description:
Sets the wait time between the calibration and the last button touch
[7:0] ETC_WAIT[7:0]:
ETC wait time = ETC_Wait[7:0] *64 + sensor clock period
A "non-touch" condition must persist for this wait time, before an ETC operation is carried out
Range: 5 mS - 20 s
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Capacitive touch module registers
STMPE321
CAL_INTERVAL
7
6
Calibration interval
5
4
3
2
1
0
CAL_INTERVAL
Address:
0x22
Type:
R/W
Reset:
0x30
Description:
Calibration interval
[7:0] CALIBRATION INTERVAL:
Interval between calibration = calibration interval [7:0] * sensor clock period * 50
Range: 4 ms - 16 s
INTEGRATION TIME
7
6
Integration time
5
4
3
2
1
INTEGRATION_TIME[7:0]
Address:
0x23
Type:
R/W
Reset:
0x0F
Description:
Integration time
[7:0] Integration time in AFS mode
Total period of integration = sensor clock period * integration time [7:0]
78 µs - 320 ms
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STMPE321
Capacitive touch module registers
CTRL
7
Control
6
5
4
RESERVED
Address:
0x25
Type:
R/W
Reset:
0x00
Description:
Control
3
2
1
0
F2A
HDC_U
HDC_C
HOLD
[7:4] RESERVED
[3] F2A:
Write '1' to force device to remain in ACTIVE state at all times
[2] HDC_U:
Write '1' to perform unconditional host driven calibration
Cleared to '0' when calibration is completed
Only applicable HOLD is '1'
[1] HDC_C:
Write '1' to perform conditional host driven calibration
Calibration is performed if and only if no touch is detected
Cleared to '0' when calibration is completed
Only applicable HOLD is '1'
[0] HOLD:
'0' to enable ETC
'1' to disable ETC
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Capacitive touch module registers
STMPE321
INT_MASK
7
Interrupt mask
6
5
4
RESERVED
3
2
EOC
1
0
RESERVED
Address:
0x26
Type:
R/W
Reset:
0x08
Description:
Writing '1' to this register disables the corresponding interrupt source.
[7:4] RESERVED
[3] EOC:
End of calibration
This interrupt occurs on both automatic and forced calibration
[2:0] RESERVED
INT_CLR
7
Interrupt clear
6
5
RESERVED
4
3
2
EOC
1
0
RESERVED
Address:
0x27
Type:
R/W
Reset:
0x00
Description:
Writing '1' to this register clears the corresponding interrupt source in INT_PENDING
register.
[7:4] RESERVED
[3] EOC:
End of calibration
This interrupt occurs on both automatic and forced calibration
[2:0] RESERVED
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STMPE321
Capacitive touch module registers
FILTER_PERIOD
7
6
Filter period
5
4
3
2
1
0
FILTER_COUNT
Address:
0x28
Type:
R/W
Reset:
0x00
Description:
Filter period.
[7:0] FILTER_COUNT:
Additional filter to stabilize touch output in AFS mode.
AFS touch output is monitored for Filter Count [7:0] times every integration time. For each time
a "touch status" is detected, an internal "Filter Counter" is incremented once. This counter
value is then compared with Filter Threshold (register 0x29).
FILTER_THRESHOLD
7
6
5
Filter threshold
4
3
2
1
0
FILTER_THRESHOLD
Address:
0x29
Type:
R/W
Reset:
0x00
Description:
Filter threshold.
[7:0] FILTER_THRESHOLD:
An internal "Filter Counter" is compared with Filter Threshold [7:0] to determine if a valid touch
has occurred.
REFERENCE_DELAY
7
6
Reference delay
5
RESERVED
4
3
2
1
0
REFERENCE_DELAY
Address:
0x2A
Type:
R/W
Reset:
0x00
Description:
Shifting of capacitive sensor dynamic range. The capacitance value set into this
register is in effect, equivalent to capacitor connected to the A_Ref pin.
[7] RESERVED
[6:0] REFERENCE_DELAY:
Valid range = 0-127
Each step represents capacitance value of 0.04 pF
Warm reset is required after this value is updated
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Capacitive touch module registers
STMPE321
TVR
7
Touch variance setting
6
5
4
3
RESERVED
2
1
0
TVR
Address:
0x30 - 0x32
Type:
R/W
Reset:
0x08
Description:
Touch variance setting
[7] RESERVED
[6:0] TVR:
Setting TVR between 0-99
A high TVR value decreases sensitivity of the sensor, but increases its tolerance to ambient
noise
A small TVR value increases the sensitivity
EVR
7
Environmental variance
6
5
4
3
RESERVED
2
1
0
TVR
Address:
0x40
Type:
R/W
Reset:
0x04
Description:
Environmental variance setting.
[7] RESERVED
[6] EVR:
EVR is used to detect "Non-Touch" condition
STRENGTH_THRESHOLD
7
6
5
Strength threshold
4
3
2
STRENGTH_THRESHOLD
Address:
0x50 - 0x52
Type:
R/W
Reset:
0x01
Description:
Strength threshold.
[7:0] STRENGTH_THRESHOLD:
Setting threshold to be used in AFS mode to determine valid touch
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0
STMPE321
Capacitive touch module registers
STRENGTH
7
Strength
6
5
4
3
2
1
0
STRENGTH
Address:
0x60 - 0x62
Type:
R
Reset:
0x00
Description:
The number of times a sensed capacitance exceeds the calibrated reference
impedance
[7:0] STRENGTH:
Read-only field
Counts the number of times a sensed impedance exceeds calibrated reference impedance
and integration time. Maximum strength equals Integration Time [7:0]
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Capacitive touch module registers
STMPE321
CALIBRATED_IMPEDANCE
7
6
5
Calibrated impedance
4
3
2
1
0
CAL_IMPEDANCE
Address:
0x70 - 0x72
Type:
R
Reset:
0x00
Description:
Calibrated impedance is a reference value maintained by the device.
[7:0] CALIBRATED IMPEDANCE:
Calibrated reference impedance
IMPEDANCE
7
Impedance
6
5
4
3
2
1
0
IMPEDANCE
Address:
0x80 - 0x82
Type:
R
Reset:
0x00
Description:
Impedance is the instantaneous impedance value seen at the input pin of each
capacitive sensing pin.
[7:0] IMPEDANCE:
Currently sensed impedance. This impedance reading decreases with the increase of the
capacitance at the sensing channel.
When this register reads 0x7F, reference capacitance should be reduced.
When this register reads 0x00, reference capacitance should be increased.
TINT_PENDING
7
Interrupt pending
6
5
RESERVED
4
3
EOC
Address:
0x92
Type:
R
Reset:
0x00
Description:
Reflects the status of each interrupt source.
[7:4] RESERVED
[3] EOC:
End of calibration
[2:0] RESERVED
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2
1
RESERVED
0
STMPE321
9
Maximum ratings
Maximum ratings
Stressing the device above the rating listed in the “absolute maximum ratings” table may
cause permanent damage to the device. These are stress ratings only, and operation of the
device at these or any other conditions above those indicated in the operating sections of
this specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
Table 11.
Absolute maximum ratings
Value
Symbol
Parameter
Unit
Min
Typ
Max
VCC
Power supply
−
−
2.5
V
VESD
ESD protection on each GPIO/touch pin
−
−
8
kV
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Electrical specifications
10
STMPE321
Electrical specifications
Table 12.
DC electrical characteristics (-40 - 85 °C unless otherwise stated)
Value
Symbol
Test condition
Unit
Min
Typ
Max
1.65
-
1.95
V
VCC
Core supply voltage
Ihibernate
HIBERNATE current
No touch sensing
capability
-
1.8
3.0
µA
Isleep
SLEEP current
Touch sensing active,
no touch
-
27
43
µA
Iactive
ACTIVE current
100% touch activity
-
280
470
µA
VIL
Input voltage low state
VCC=1.8 V
-0.3V
-
0.2VCC
V
VIH
Input voltage high state
VCC=1.8 V
0.8Vcc
-
VCC+0.3V
V
VOL
Output voltage low state
VCC=1.8 V,
IOUT= 4 mA
-0.3V
-
0.25VCC
V
VOH
Output voltage high
state
VCC=1.8OUTV,
IOUT = 4 mA
0.75Vcc
-
VCC+0.3V
V
VOL
(I2C)
Output voltage low state IOL=4 mA
-0.3V
-
0.25VCC
V
Ileakage
10.1
Parameter
Input leakage (GPIO)
GPIO as input,
VIN = 2.0 V
-
-
0.5
µA
Input leakage
(SCL, SDA, RST)
VIN = VCC = 1.95 V
-
-
0.5
µA
Capacitive sensing characteristics
Table 13.
Capacitive sensing characteristics
Value
Symbol
Test condition
Unit
Min
Typ
Max
Res
Capacitive
measurement
resolution
Aref = not connected
-
40
-
fF
DR
Dynamic range
Aref = not connected
-
5.1
-
pF
Linearity of sensor
Aref = not connected
Maximum deviation
calculated from full scale
capacitance
measurement data
-
10
-
%
L
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Parameter
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STMPE321
11
Package mechanical data
Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
Figure 8.
Package outline for QFN12 (2.2 x 1.5 x 0.5 mm) - 0.40 mm pitch
8118749_QFN12
1. Drawing not to scale.
2. Dimensions are in millimeters.
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Package mechanical data
Table 14.
STMPE321
Mechanical data for QFN12 (2.2 x 1.5 x 0.5 mm) - 0.40 mm pitch
Millimeters
Symbol
Figure 9.
Min
Typ
Max
A
0.50
−
0.60
A1
0
−
−
b
0.15
−
0.25
D
−
1.50
−
E
−
2.20
−
e
−
0.40
−
L
0.35
−
0.45
Footprint recommendations for QFN12 (2.2 x 1.5 x 0.5 mm) - 0.40 mm
pitch
1. Drawing not to scale.
2. Dimensions are in millimeters.
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STMPE321
Package mechanical data
Figure 10. Carrier tape for QFN12 (2.2 x 1.5 x 0.5 mm) - 0.40 mm pitch
785978-J
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Package mechanical data
STMPE321
Figure 11. Reel information for QFN12 (2.2 x 1.5 x 0.5 mm) - 0.40 mm pitch
7875978
1. Drawing not to scale.
2. Dimensions are in millimeters
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STMPE321
12
Revision history
Revision history
Table 15.
Document revision history
Date
Revision
Changes
19-Jun-2009
1
Initial release.
29-Jul-2009
2
Deleted “internal regulator” from the Features section.
Modified: Figure 1, Chapter 2, Figure 4. Chapter 4 and
Chapter 5, Chapter 1.3 and Chapter 7.
12-Aug-2009
3
Modified: Figure 4.
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STMPE321
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