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D
E
F
Microchip Technology Inc.
2355 West Chandler Blvd.
Chandler, Arizona 85224-6199
480-792-7200
RN52 Bluetooth Audio Module
Command
Specifications
Revision History
REV DATE
A
Author
2/11/2013 Dale Loia
B
C
2/14/2013 Dale Loia
2/16/2013 Dale Loia
DESCRIPTION OF CHANGE
Initial Draft. Replaces “RN-52 commanset.95.docx”
Removed F command, table 1 corrections, state machine diagram
Fixed error in table
G
H
I
J
2/18/2013 Dale Loia
3/13/13 Dale Loia
3/26/13 Dale Loia
3/26/13
3/29/13
4/16/13
5/12/13
Dale Loia
Dale Loia
Dale Loia
Dale Loia
Re-ordered E command, “-“write only,
New commands
Changed I/O configuration commands from action to SET parameters.
Clarified parameter size and format for I/O commands.
Firmware Release 1.09:
Restored I/O commands as actions, added more tables and examples
Firmware Release 1.11:
Updated release history; updated extended features “S%”
Firmware Release 1.13.03
Hardened B and K,FF, and timeout flag the connection commands.
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 1
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 2
Table of Contents
DFU – Device Firmware Update ................................................................... 12
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 3
1 Introduction
This document describes the operation of the RN-52 Bluetooth Audio module command interface. The command interface operates over the Serial UART port. The UART has 2 modes, (1) DATA mode and (2) COMMAND mode.
In DATA mode, the UART operates as a raw serial bi-directional data pipe when connected to a remote BT client using SPP or Wireless iAP profiles.
2 GPIOs
The RN52 has 11 GPIO lines. Several GPIO are reserved for specific functions during bootup and run time. The table 1 below lists the GPIOs and their functions. Two GPIOs are used at
Table 1: Default GPIO Assignment and Functions
GPIO Function
2
Output: Toggles from HIGH to LOW for 100ms to indicate a state change in the RN52. MCU should enter CMD mode and poll state register using “Q” action command.
This IO is reserved and NOT available for general use at runtime.
3
INPUT @ bootup: enter DFU MODE at boot time if
USB device powers VBUS. PIO3 requires 47K to ground and 22K to USB VBUS if USB VBUS is supplying power to main board.
4
INPUT @ boot up: enter factory reset mode if driven LOW.
5
INPUT @ runtime, used for VOL-UP button. LOW is active
6
INPUT/OUTPUT at runtime
Use
Runtime,
RESERVED
Bootup,
Config
Bootup,
Config
Runtime,
Config
Runtime,
Config
Bootup,
Config
Runtime,
RESERVED
7
INPUT @ boot time, driven LOW will set UART baud rate to 9600, HIGH default baud 115200
9
INPUT: Driven LOW will put UART in CMD mode, other left to float HIGH, UART is in data mode.
This IO is reserved and NOT available for general use at runtime.
10
INPUT @ runtime, used for VOL-DN.button, LOW is active
11
INPUT @ runtime, used for PREV-TRACK button, LOW is active
12
INPUT @ runtime, used for NEXT-TRACK button, LOW is active
13
INPUT @ runtime, used for PLAY/PAUSE button, LOW is active
Runtime,
Config
Runtime,
Config
Runtime,
Config
Runtime,
Config
2.1 Status Change Notification via PIO2
The RN52 drives PIO2 (as an output) to notify an external MCU of an event or status change.
Status changes include changes to profile connections or voice call connections. The MCU
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 4
should enter command mode and issue the “Q” command to retrieve latest status. See Section
3 for more information regarding status changes.
Firmware 1.02 to 1.11
PI02 is held LOW for 100ms to indicate a change, or event, has occurred. The timing diagram below illustrates three event notifications.
High
PIO2
Low
100ms 100ms 100ms
Figure 1: PIO2 Event Notification 1.12 and below
Firmware 1.12 or later
Starting with firmware 1.13 and later, PI02 is held LOW for each new event and remains latched LOW until “Q” command unlatches PIO2 back to HIGH.
High
PIO2
Low
RN 52 UART TX
Event Latched
Event Unlatched
Q\r
Event Latch Unlatched
Q\r
Figure 2: PIO2 Event Notification
2.2 Command Mode via PIO9
The RN52 monitors PIO9 (as an input) to determine whether data traversing the UART is routed to active Bluetooth SPP (serial port profile) connection or to the command console.
When PIO9 is held high, the UART enters command mode. In command mode all data enters
UART is routed to command console where the module can be configured and queried for status using the ASCII commands.
High
PIO9
Low
Data Mode Command Mode Data Mode
CMD\r\n END\r\n
RN 52 UART RX
Figure 3: PIO9 pull low routes UART traffic to command console
For applications when an MCU controls PIO9 and commands over UART, the MCU should monitory UART RX line for the following five character strings: “
CMD\r\n” and
“
END\r\n” immediately after driving PIO9.
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 5
Use the following state diagram as a guideline for designing code to monitor PIO9 and command states.
“CMD\r\n” received
PIO9 set LOW
Wait for
“CMD\r\n”
DATA Mode
Ready
CMD
Mode
Ready
“END\r\n” received
Wait for
“END\r\n”
PIO9 set HIGH
Figure43: State Diagram for entering and exiting CMD mode
3 Event/Status Register
The “Q\r” action command returns a multi-byte list, where each value is expressed as “00”-
“FF”. The byte list is ordered little endian (byte 0 LSB, byte N last) terminated by carriage return and line feed characters (\r\n).
Table 1 describes the current status bytes. For example, the byte string “
0C16\r\n” indicates
A2DP and HFP profiles are connected and connection state is “ActiveCall (6)” and Audio
Mute/Hold event was received from phone.
Connection state value (bits 0-3) do NOT change unless the module status changes.
Event bits 4-6 in BYTE[1] are cleared when “Q” is issued.
The module drives GPIO2 LOW for 100ms to notify Docking Station that the event/status register has been changed.
BYTE0
Bit
0
1
2
3
4-7
BYTE1
Bit
0-3
4
5
6
7
Table 1: Profile Status and Connection
Description iAP Wireless active connection to remote device
SPP active connection to remote device
A2DP active connection to remote device
HFP/HSP active connection to remote device
RESERVED
Description
Connection States: 0-15, see table 2 below
HFP audio volume level change from audio gateway
(phone), use “Y,0” to retrieve volume level
HFP audio microphone level change from audio gateway (phone), use “Y,1” to retrieve microphone level
HFP Voice mute/hold event triggered by Phone
Connection timeout flag: used to indicate if “B” re-connect command time out. This flag is cleared
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 6
after “Q” status is returned.
Value State
0 Limbo
Table 2: Connection States in Byte 1, bits 0-3
Description logically off but physically on
1 Connectable
2
3
4
5
6
7
8
9
Connectable and
Discoverable
Connected
Outgoing Call
Establish
Incoming Call
Establish
Active Call On
Handsfree
Test Mode
Three Way Call
Waiting
Three Way Call On
Hold
10 Three Way Call
Multi Call
11 Incoming Call On connectable - page scanning connectable and discoverable - page and inquiry scanning connected to an AG connected AG has an outgoing call in progress connected AG has an active call in progress and the audio is in the headset connected AG has an active call in progress and the audio is in the headset headset is in test mode connected AG has an active call and a second call on hold connected AG has an active call and a second call on hold connected AG has an active call and a second call on hold connected AG has an incoming call on hold Hold
12 Active Call On
Handset connected AG has an active call and
13 Audio Streaming headset is streaming A2DP audio
14 Low Battery the audio is in the handset low battery state
4 Set/Get Commands
The following parameters can be written and read from command console using SET & Get commands. SET and GET use the following syntax where the parameter is a single character.
:
“S<char>,<value>\r”
“G<char>\r”
Set a paramater
Read a parameter
The parameter <char> is a single character. All SET commands are non-blocking and will return immediately. Set commands DO NOT TAKE EFFECT until module is rebooted
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 7
with “R,1” command unless noted otherwise. Not all set parameters are readable with a get.
All commands respond with “
AOK,<opt msg>\r\n” for success, or “ERR,<opt msg>\r\n” if command fails. <opt msg> is optional message text.
Table 3: Set/Get parameters
Parameter Description
A,<decimal>
Authentication Mode
Example: “SA,4\r” set module to legacy PIN code. <decimal>
0=open, 1=keyboard I/O, 2=just works, 4=pin code, Default: 0x1 (keyboard)
C,<hex>
D,<byte>
F,1
K,<byte>
Class of Device
Set COD for Bluetooth device. This is 24-bit
(6 byte) hex value. Default is 240407, corresponding to
Discovery Mask
Byte value to enable specific profiles that can be discovered by remote Bluetooth hosts.
See Byte0 definition for profile value.
Default is FF, all profiles.
Factory Default
Sets all parameters to factory default values. The changes do not take effect until module is rebooted. This is a write-only parameter.
Example: “SF,1\r” invokes factory default.
Connection Mask
N,<string>
P,<string>
-,<string>
|,<byte>
Byte value to enable specific profiles that can be connected by remote Bluetooth hosts.
See Byte0 definition for profile value.
Default is FF, all profiles.
Bluetooth Name
Sets the Bluetooth friendly name advertised during an inquiry scan. Name can be up to 16 characters.
PIN Code
Sets four digit PIN code used for legacy pairing.
Serialized Name
Example: “S-,AUDIO\r” sets Bluetooth name to friendly address “AUDIO-b1b0” where b0 and b1 hex values for first two bytes (right most) of MAC address i.e. “AUDIO-51A2”.
NOTE: this is a write only parameter
Audio Route
Set the route for audio output. Values are:
00 – Analog (default)
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 8
^,<dec>
%,<hex8>
01 – I2S (variable sample rate, 24bit sample, left justified, 1 delay)
02 – S/PDIF
Example: “S|,02\r” set audio output to SPDI/F at next reboot.
Automatic Shutdown on Idle
0- Feature disable, on forever
1-600 seconds of idle time (not-connected)
Extended Feature
Bit 0 – enable AVRCP buttons for EK
Bit 1 – enable reconnect on power-on
Bit 2 – discoverable on start up
NOTE: Extended features default value is set at factory to 00 for RN52 modules and 07 for
RN52EK. The “SF,1” does NOT change this value. It must be changed with “S%,<hex8>” command.
5 Action Commands
Action commands make immediate changes to the module and do NOT require reboot. The format of action command is as follows:
<char>,<optional argument>\r
All Action commands are non-blocking and will return immediately. If background processing is required then event notification should be used to determine if operation succeeded or failed.
All commands respond with “
AOK,<opt msg>” for success, or “ERR,<opt msg>” if command fails. <opt msg> is optional message text.
A,<phone>
AV+
AV-
AT+
AT-
Description
Initiate Voice Call
Sends command to Phone to initiate a call to
<phone>, where phone is a string max 25 characters; example “A,14083955300”, ERR returned if connection state is NOT (0,1,2).
Volume UP
Sends AVRCP volume up command to AG or BT host.
Volume UP
Sends AVRCP volume down command to AG or BT host.
Next Track
Sends AVRCP next track command to AG or BT host.
Previous Track
Sends AVRCP previous track command to AG or
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 9
AP
B
C
D
E
BT host.
Play/Pause Toggle
Sends AVRCP play/pause command to AG or BT host.
Reconnect to Profiles
Attempt to reconnect profiles to most recently paired & connected device. Reconnect will be attempted on the profiles specified in the connection mask. See the “SK,<value>” command.
Use “Q” to retrieve BT profile connection status in byte 0 (bits 0-3) value. ERR returned if module has not been previously connected or connection mask is set to 00 (00 means module is unconnectable).
Accept Incoming Voice Call
Use “Q” to retrieve call status Byte[1]:bits
0-3 value. ERR returned if call status is NOT set to incoming call established (5).
Display Active Configuration
Display configuration settings.
Drop or Reject Call
Terminate an active call or reject an incoming call. Call status must be either (1)
H
Incoming call, (2) active call, otherwise ERR is returned.
Display Help Text
Displays help text. Useful when accessing command console from terminal emulator.
HV,<decimal> Set AG Volume Level
Sends volume level to AG (audio gateway) to adjust voice call volume. This command is used to synchronize volume levels. Level in decimal integer 0-15; example “HV,8”. Conform to HFP Specification 1.6 4.28.2.
I@
I@,<hex16>
I&
I&,<hex16>
Configure GPIO direction
16-bit mask used to set GPIO direction, bit on for output, bit off for input
If no argument specified the current configuration is returned
GPIO level and input pull-up configuration
Bit on is logical high, bit off logical low
If no argument specified the current levels are returned.
The 16-bit <hex16> value is PIO bit map (bit4
= PIO4).
When PIO is configured as output, I&,<hex16> drives the level high for PIO specified in
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 10
K,<byte>
Q
M,<enable>
R,1
Y,<0,1>
<hex16>.
When PIO is configured as input, I& configures the PIO to use a pull-up (bit set) or pull-down(bit clear).
Disconnect Profiles
Drop connections specified on profile byte
(see Byte 0, bit 0-3)
Show Connection Status
Display byte (ascii hex) string indicating connected profiles, connection states, and other events. See section 3.
Hold/Mute Current Call
Places active call on hold/mute or toggles hold/mute.
“M” toggles hold/mute on/off
“M,0” – unmute call. ERR returned if call status is NOT Active Call (2).
Reboot Module
Drops all active connections and reload stored values from previous “S” (set) commands.
Gain Level (Speaker or Microphone)
In response to bit 14 & 15 in event status register, this command returns either last speaker or microphone level as 0-15 decimal value sent from audio gateway.
“Y,0” returns speaker volume
“Y,1” returns microphone level
V
Display Firmware Version
Displays firmware level.
@,<decimal>
Discoverability Enable/Disable
Enables or disables discoverability of
+ module.
“@,0”, disable discoverability
“@,1”, enable discoverability
Local Echo Toggle
Helpful when accessing the command console from terminal emulator
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 11
6 Using GPIOs
The RN52 GPIO are configurable as action commands. The IO configuration does not persist and must be through “I@” and “I&” commands when module is running.
A 16-bit mask is used to refer each GPIO in the “I@” an “I&” commands. The default state is undefined until they are configured. Default Mask as boot time. The available
GPIO are shown below. Any GPIO grayed out row is not available for general purpose use.
GPIO MAP
PIO
0
1
2
Mask Description
0001
0002
0004
N/A
N/A
RESERVED, output only used to drive state change notifications. The mask value “I@” will always return “0004”
7
8
9
3
4
5
6
0008
0010
0020
0040
0080
0100
0200
Volume up in AVRCP mode
N/A
RESERVED, input only used to detect
CMD mode entry.
0400 Volume down in AVRCP mode
10
11
12
13
14
15
0800
1000
2000
4000
8000
Previous track in AVRCP mode
Next Track in AVRCP mode
Pause/Play in AVRCP mode
N/A
N/A
WARNING for RN52-EK (AVRCP mode enabled):
It is not recommended to enable the “S%,01” AVRCP buttons and configure the button PIOs
(5,10-13) as outputs (i.e.“I@,3C20”). Pressing the buttons in this configuration may damage the RN52 module.
PIO INPUT/OUTPUT EXAMPLE:
This example assume the AVRCP mode is disabled (S%,00). To configure GPIO 5-7 as inputs with pull up, and 12,13 outputs, issue the following commands.
“I@,3000\r” // configured 12 & 13 as outputs, the rest are inputs
“I@\r” // read the PIO mask
“3004\r\n” // PIO2 (bit2=0004) will always be configured as output
“I&,20E0\r” // enable internal pull up resistor on 5,6,7,drive 13 high, clear remaining levels
7 DFU – Device Firmware Update
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 12
Figure 5: schematic USB DFU port and PIO3
Device Firmware Update (DFU) uses the USB port to update the firmware in the RN52.
Implement the DFU feature is highly encouraged as firmware updates offer new features which enhance the functions of the RN52 module. Follow the reference design in the figure
X. When an external USB host is plugged into DFU port and energized VBUS, the RN52 enters DFU mode when module is rebooted or powered up. The line C4 and D1 to VBUS input on voltage regulator (see full reference design schematic in data sheet) is not need if customer board is not being power from USB VBUS.
A 47K pull down resistor (See R2 on figure x) is required on PIO3 even if DFU USB
reference is not used.
7.1 Using DFU Loader utility
TBD
8 Factory Default Using PIO4
[step by step] TBD
9 Firmware Release Revision
Version Description
1.08
1.09
First release on RN52-EK, Mar 2013
Added new commands:
“I@” action command to configure GPIO
“I&” action command to set/get GPIO levels
“S%”, to configure extended features
1.10
1.11
1.12
1.13
Modified “S%” extended features to avoid factory default via “SF,1” command. Extended features must be set with “S%,<byte>” command. This was done to support RN52EK configuration on production line.
Fixed a issue with “B” command not reconnecting iAP profile
Changed GPIO2 from pulse to latched/unlatch mechanism
Hardened K,FF and B, a
Mar 2013
Apr 2013
Apr 2013
Apr 2013
Apr 2013
May 2013
Microchip Technology Inc
RN52 Command Specifications
Rev J pg. 13
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