STMicroelectronics STM32 STM32 microcontroller Application note

AN3116
Application note
STM32™’s ADC modes
and their applications
Introduction
STM32 microcontrollers have one of the most advanced ADCs on the microcontroller
market. You could imagine a multitude of applications based on the STM32 ADC features.
Some ADC modes are provided to simplify measurements and give efficient results in
applications such as motor control.
This application note provides help for ADC users to understand some advanced modes
offered in the STM32 microcontrollers, and to quick start development. Each of the
described modes is provided with an example of application to better understand how to use
them. Most modes come with a basic firmware to make it easier to understand the ADC
configuration.
This application note is divided into two sections: independent modes and dual modes. The
first section describes modes used with a single ADC. The second section describes modes
that should be used with two ADCs (ADC1 and ADC2 working jointly).
This application note does not describe the ADC modes that result from the combination of
other modes.
March 2010
Doc ID 16840 Rev 1
1/18
www.st.com
Contents
AN3116
Contents
1
Independent modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
1.2
1.3
1.4
1.5
2
1.1.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Multichannel (scan), single conversion mode . . . . . . . . . . . . . . . . . . . . . . 5
1.2.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Single-channel continuous conversion mode . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.2
Example of applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Multichannel (scan) continuous conversion mode . . . . . . . . . . . . . . . . . . . 7
1.4.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Injected conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Dual modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1
2.2
2.3
2.4
2.5
2/18
Single-channel, single conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Dual regular simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Dual fast interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Dual slow interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Dual alternate trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Dual combined regular/injected simultaneous mode . . . . . . . . . . . . . . . . 14
2.5.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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Contents
2.6
Dual combined: injected simultaneous + interleaved mode . . . . . . . . . . . 14
2.6.1
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.6.2
Example of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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List of figures
AN3116
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
4/18
Single-channel, single conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
ADC sequencer converting 7 channels with different configured sampling
times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Multichannel, single conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Single-channel, continuous conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Multichannel, continuous conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Injected conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Dual regular simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Simultaneous measurement of voltage and current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Dual fast interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Dual slow interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Dual alternate trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Dual combined regular/injected simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Dual combined: injected simultaneous + interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . 15
UPS system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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Independent modes
1
Independent modes
1.1
Single-channel, single conversion mode
1.1.1
Description
This is the simplest ADC mode. In this mode, the ADC performs the single conversion
(single sample) of a single channel x (refer to Figure 1.) and stops after completion of the
conversion.
Note:
This application note is not delivered with a firmware example of this mode.
Figure 1.
Single-channel, single conversion mode
3TART
#(X
3TOP
AI
1.1.2
Example of application
This mode can be used for the measurement of a voltage level to decide if the system can
be started or not. Measure the voltage level of the battery before starting the system: if the
battery has a low level, the “low battery” message appears. In this case, do not start the
system.
1.2
Multichannel (scan), single conversion mode
1.2.1
Description
This mode is used to convert some channels successively in independent mode. With the
ADC sequencer, you can use this ADC mode to configure any sequence of up to 16
channels successively with different sampling times and in different orders. You can for
example carry out the sequence shown in Figure 2. In this way, you do not have to stop the
ADC during the conversion process in order to reconfigure the next channel with a different
sampling time. This mode saves additional CPU load and heavy software development.
Figure 2.
Note:
ADC sequencer converting 7 channels with different configured sampling
times
This application note is not delivered with a firmware example of this mode.
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Independent modes
Figure 3.
AN3116
Multichannel, single conversion mode
3TART
#(X
#(N
3TOP
1.2.2
AI
Example of application
This mode can be used when starting a system depends on some parameters like knowing
the coordinates of the arm’s tip in a manipulator arm system. In this case, you have to read
the position of each articulation in the manipulator arm system at power-on to determine the
coordinates of the arm’s tip.
This mode can also be used to make single measurements of multiple signal levels (voltage,
pressure, temperature, etc.) to decide if the system can be started or not in order to protect
the people and equipment.
It can likewise be used to convert signals coming from strain gauges to determine the
directions and values of the different strains and deformations of an object.
1.3
Single-channel continuous conversion mode
1.3.1
Description
The single-channel continuous conversion mode converts a single channel continuously
and indefinitely in regular channel conversion.
The continuous mode feature allows the ADC to work in the background. The ADC converts
the channels continuously without any intervention from the CPU. Additionally, the DMA can
be used in circular mode, thus reducing the CPU load.
Note:
An example of firmware is provided with this application note: SingleChannelContinuous.
The example uses two methods: DMA and interrupts. To select either method, simply
comment or uncomment #define USE_DMA_Transfer in the main.c file.
Figure 4.
Single-channel, continuous conversion mode
3TART
#(X
AI
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1.3.2
Independent modes
Example of applications
This ADC mode can be implemented to monitor a battery voltage, the measurement and
regulation of an oven temperature, etc.
In the case of the oven temperature regulation, the temperature is read and compared to the
temperature set by the user. When the oven temperature reaches the desired temperature,
the heating resistor is powered off.
1.4
Multichannel (scan) continuous conversion mode
1.4.1
Description
The multichannel, or scan, continuous mode can be used to convert some channels
successively with the ADC in independent mode. With the sequencer, you can configure any
sequence of up to 16 channels successively with different sampling times and different
orders. This mode is similar to the multichannel single conversion mode except that it does
not stop converting after the last channel of the sequence but it restarts the conversion
sequence from the first channel and continues indefinitely.
Figure 5.
Multichannel, continuous conversion mode
3TART
#(X
#(N
AI
1.4.2
Example of application
This mode can be used to monitor multiple voltages and temperatures in a multiple battery
charger. The voltage and temperature of each battery are read during the charging process.
When the voltage or the temperature reaches the maximum level, the corresponding battery
should be disconnected from the charger.
1.5
Injected conversion mode
1.5.1
Description
This mode is intended for use when conversion is triggered by an external event or by
software.
The injected group has priority over the regular channel group. It interrupts the conversion of
the current channel in the regular channel group.
Note:
An example of firmware is provided with this application note: Indep_InjectedGroup.
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Independent modes
AN3116
Figure 6.
!$#
Injected conversion mode
#(
#(
!$#
)NJECTED
TRIGGER
#(
2EGULARSIMULTANEOUSMODE
INTERRUPTEDBYTHEALTERNATE
TRIGGERMODE
#(
#(
%NDOFINJECTED
CONVERSION
ON!$#
3AMPLING
#ONVERSION
AI
1.5.2
Example of application
This mode can be used to synchronize the conversion of channels to an event. It is
interesting in motor control applications where transistor switching generates noise that
impacts ADC measurements and results in wrong conversions. Using a timer, the injected
conversion mode can thus be implemented to delay the ADC measurements to after the
transistor switching.
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2
Dual modes
Dual modes
Dual modes are available in STM32 microcontrollers that feature two ADCs: ADC1 master
and ADC2 slave. ADC1 and ADC2 triggers are synchronized internally for regular and
injected channel conversion. ADC1 and ADC2 work together.
In some devices, there are up to 3 ADCs: ADC1, ADC2 and ADC3. In this case ADC3
always works independently, and is not synchronized with the other ADCs.
Note:
Do not sample the same channel on the two ADCs at the same time, this would introduce
conversion errors.
2.1
Dual regular simultaneous mode
2.1.1
Description
The dual regular simultaneous ADC mode is used to perform two conversions
simultaneously owing to the synchronization of ADC1 and ADC2. Each ADC converts a
channel sequence (with scan enabled and the sequencer of each ADC configured) or
converts a single channel (scan disabled). The conversion can be started with an external
trigger or by software. In this mode, the conversion results of ADC1 and ADC2 are stored in
ADC1’s data register (32-bit format). Figure 7 shows how ADC1 and ADC2 convert two
sequences simultaneously. ADC1 converts a sequence of 16 channels successively:
channel 15 to channel 0 and ADC2 converts a sequence of 16 channels successively:
channel 0 to channel 15.
Note:
This application note does not provide a firmware example. However the STM32 firmware
library provides an example of this mode at the following path:
\Project\STM32F10x_StdPeriph_Examples\ADC\RegSimul_DualMode.
Figure 7.
Dual regular simultaneous mode
!$#
#(
#(
#(
#(
!$#
#(
#(
#(
#(
4RIGGERFOR
REGULARCHANNELS
#(
#(
%NDOFCONVERSION
ON!$#AND!$#
3AMPLING
#ONVERSION
AI
2.1.2
Example of application
The dual regular simultaneous mode can be used in applications where two signals should
be sampled and converted at the same time. For example, to measure and plot the singlephase or three-phase instantaneous electrical power: pn(t) = un(t) × in(t).
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Dual modes
AN3116
In this case, the voltage and current should be measured simultaneously and then the
instantaneous power, which is the product of un(t) and in(t), should be computed.
Figure 8 shows how to measure a power using the two ADCs in dual regular simultaneous
mode.
To measure a single-phase power, ADC1 and ADC2 are used with two channels (1 channel
for the voltage and 1 channel for the current).
To measure a three-phase power, ADC1 and ADC2 are used with 6 channels (3 channels
for the voltage and 3 channels for the current).
Figure 8.
Simultaneous measurement of voltage and current
3INGLEPHASECASE
!$#
#(XUT
#(XUT
#(XUT
!$#
#(YIT
#(YIT
#(YIT
PTUT§T#(X§#(Y
4HREEPHASECASE
!$#
#(UUPH T
#(VU PH T
#(WU PH T
!$#
#(XI PH T
#(YI PH T
#(ZI PH T
P PH TUPHTIPHT#(U§#(X
P PH TUPHTIPHT#(V§#(Y
P PH TUPHTIPHT#(W§#(Z
AI
2.2
Dual fast interleaved mode
2.2.1
Description
The dual fast interleaved ADC mode is intended for the conversion of one channel. ADC1
and ADC2 convert the selected channel alternately with a period of 7 ADC clock cycles.
This means that the channel is converted every 7 clock cycles. Each ADC converts the
channel every 14 ADC clock cycles. With a 14 MHz ADC clock, it is thus possible to reach
2 Msamples per second: 14 MHz/7 = 2 MHz (sampling frequency). The conversion can be
started by external trigger or by software and the conversion results of ADC1 and ADC2 are
stored into ADC1 data register (32-bit format).
The maximum allowed sampling time is 7 ADC clock cycles to avoid the overlap between
the ADC1 and ADC2 sampling phases in the event that they convert the same channel. This
means that the only allowed sampling time is 1.5 cycles.
Note:
10/18
1
It is highly recommended to use DMA instead of interrupts to avoid the loss of data.
2
An example of firmware is provided with this application note: Dual_FastInterleaved.
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Dual modes
Figure 9.
Dual fast interleaved mode
!$#
#(
#(
#(
3AMPLING
%NDOFCONVERSIONON!$#
#ONVERSION
!$#
#(
4RIGGERFOR
REGULAR
CHANNELS
#(
!$#CLOCKCYCLES
#(
%NDOFCONVERSIONON!$#
AI
2.2.2
Example of application
This mode is used to speed up the sampling rate of the ADC when 2 Msamples/second are
needed with 1.5 cycle of sampling time. ADC1 and ADC2 convert the same channel
alternately to reduce the conversion time. While ADC1 samples channel CHx, ADC2
converts the previous sample.
For example if a signal to be converted has a maximum frequency of 800 kHz, the sampling
rate frequency should be higher than or equal to twice the frequency of the signal to be
converted (in accordance with Shannon-Nyquist criteria). Since the maximum sampling rate
is 1 Msample/second with one ADC, the criteria cannot be met. This is solved by using the
dual fast interleaved ADC mode. In this way, the sampling rate frequency becomes
2 Msample/second since the two ADCs (ADC1 and ADC2) work alternately and sample the
signal at equal periods (7 ADC cycles).
With the dual fast interleaved ADC mode, 2 Msamples/second can be achieved with 1.5
cycles of sampling time.
2.3
Dual slow interleaved mode
2.3.1
Description
The dual slow interleaved ADC mode is intended for the conversion of one channel. ADC1
and ADC2 convert the selected channel alternately with a period of 14 ADC clock cycles.
The channel is thus converted every 14 clock cycles. Each ADC converts the channel every
28 ADC clock cycles. The conversion can be started by external trigger or by software and
the conversion results of ADC1 and ADC2 are stored into ADC1’s data register (32-bit
format).
The maximum allowed sampling time is 14 ADC clock cycles to avoid any overlap with the
next conversion. This means that the only allowed sampling times are 1.5, 7.5 and 13.5
cycles.
Continuous conversion should not be used in this mode since the ADCs would continuously
convert the selected regular channel automatically (the CONT bit should not be set in this
mode).
Note:
1
It is highly recommended to use DMA instead of interrupts to avoid the loss of data.
2
An example of firmware is provided with this application note: Dual_SlowInterleaved.
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Dual modes
AN3116
Figure 10. Dual slow interleaved mode
!$#
#(
#(
3AMPLING
%NDOFCONVERSIONON!$#
#ONVERSION
!$#
#(
4RIGGERFOR
REGULAR
CHANNEL
!$#CLOCKCYCLES
#(
%NDOFCONVERSIONON!$#
!$#CLOCKCYCLES
2.3.2
AI
Example of application
Let us assume that the signal to be converted has a maximum frequency (fin) of 500 kHz
with an impedance RAIN = 10 k. The minimum sampling rate should be
1 Msamples/second (in accordance with Shannon-Nyquist criteria).
With one ADC, the only configuration is fADC = 14 MHZ and the sampling time Ts = 1.5
cycles (Ts = ts × fADC, refer to the datasheet of the STM32 product you are using for more
details on the sampling time vs. the source impedance).
In this case, the maximum allowed impedance of the source (RAINmax) is 1.2 k. The
conversion will not be accurate since RAIN > RAINmax.
Solution
Use the ADC in dual slow interleaved mode. Each ADC sampling should be configured to
have a minimum sampling rate of 500 ksamples/second with fADC = 14 MHz.
f ADC
T TotalRate = T s + T conv = t TotalRate  f ADC = ---------------- , where:
F sRate
–
TTotalRate is the total conversion time in ADC clock cycles.
–
tTotalRate is the sum of the sampling time ts (ts = Ts/fADC) and the conversion time
tconv (tconv = Tconv/fADC)
–
Tconv is a constant equal to 12.5 cycles
Ts is the sampling time given in ADC cycles, it is equal to:
6
f ADC
14 10 - – 12.5 = 15.5 cycles , where F
T s = ---------------- – 12.5 = --------------------sRate is the sampling rate
3
F sRate
500 10
frequency.
Since Ts = 15.5 cycles is not available for the configuration (for more details about the
different available Ts values, refer to the “12-bit ADC characteristics” section in the
datasheet of the STM32 product you are using). The nearest available value is Ts = 13.5.
To know whether this value meets Shannon-Nyquist criteria, we need to calculate the
sampling rate with Ts = 13.5 and fADC = 14 MHz:
TTotalRate = 13.5 + 12.5 = 26 cycles
FsRate = fADC/TTotalRate = 14.106 / 26 = 538 kHz per ADC
Since the conversion is made with two ADCs (ADC1 + ADC2) working alternately, the
sampling rate frequency is: FsRate = 538 × 2 = 1076 kHz > 2 × fin, and so the ShannonNyquist criteria is respected.
12/18
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Dual modes
With Ts = 13.5 cycles, the maximum allowed impedance of the source (RAIN) is 19 k. Since
the source has an impedance RAIN = 10 k < 19 k the impedance condition is respected.
With a single ADC and with Ts = 1.5 (corresponding to 1.2 k), the impedance condition is
not satisfied. By using two ADCs, we have thus extended the impedance margin from
1.2 k to 19 k.
With the dual slow interleaved ADC mode, the 1 Msamples/second sampling rate is
achieved with higher input impedances.
2.4
Dual alternate trigger mode
2.4.1
Description
The dual alternate trigger ADC mode can be used only on an injected channel group. In this
mode, ADC1 and ADC2 alternately convert the injected channels on the same external
trigger. When the first trigger occurs, all injected group channels in ADC1 are converted.
When the second trigger happens, all injected group channels in ADC2 are converted and
so on. The maximum number of injected channels in the group is 4 for each ADC.
Note:
An example of firmware is provided with this application note: Dual_AlternateTrigger.
Figure 11.
Dual alternate trigger mode
STTRIGGER
!$#
RDTRIGGER
#(
THTRIGGER
THTRIGGER *%/#ON!$#
#(
#(
3AMPLING
#(
#ONVERSION
!$#
#(
NDTRIGGER
2.4.2
THTRIGGER
#(
#(
THTRIGGER
THTRIGGER
#(
*%/#ON!$#
AI
Example of application
The dual alternate trigger mode makes it possible to have sampling points as close as
possible to each other (down to 1.5 ADC cycles). This is interesting for instance in motor
control applications, where a single-shunt sensor is used for three-phase current reading. In
some cases, the PWM duty cycle of the power stage has to be limited to maintain a
minimum time slot for two consecutive conversions. If the sampling points are as close as
possible, the PWM duty cycle is maximized, which increases the voltage applied to the
motor.
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Dual modes
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2.5
Dual combined regular/injected simultaneous mode
2.5.1
Description
The dual combined regular/injected simultaneous ADC mode is a regular simultaneous
mode that allows injection. The injected channels are also converted simultaneously.
In this mode, you should convert sequences with the same length or ensure that the interval
between triggers is longer than the longest of the 2 sequences. Otherwise, the ADC with the
shortest sequence may restart while the ADC with the longest sequence is completing the
previous conversions.
Note:
An example of firmware is provided with this application note:
Dual_Combined_Reg_Inj_Sumultaneous. The example uses two methods: DMA and
interrupts. To select either method, simply comment or uncomment #define
USE_DMA_Transfer in the main.c file.
Figure 12. Dual combined regular/injected simultaneous mode
!$#
#(
!$#
#(
#(
4RIGGERFOR
REGULAR
CHANNELS
3AMPLING
#(
2EGULARSIMULTANEOUS
CONVERSIONINTERRUPTED
BYINJECTEDSIMULTANEOUS
CONVERSION
!$#
#(
#(
!$#
#(
#(
#ONVERSION
4RIGGERFORINJECTEDCHANNELS
2.5.2
#(
#(
#(
#(
#(
#(
%NDOFCONVERSIONON!$#
AND!$#
%NDOFINJECTEDCONVERSIONON!$#
AND!$#
AI
Example of application
The dual combined (regular/injected) simultaneous mode can be used to read 3-phase
currents at definite times. This mode is interesting when you read the currents of two of the
phases and you determine the current of the third phase by extrapolation since there is a
relationship between the currents of the 3 phases.
2.6
Dual combined: injected simultaneous + interleaved mode
2.6.1
Description
This mode is the combination of the dual interleaved mode (fast or slow) and the dual
injected simultaneous mode. When the regular channel is triggered, the dual interleaved
conversion starts: ADC2 makes the first conversion, then ADC1 converts the channel and
so on. When the injected channel is triggered, it interrupts the interleaved channel
conversion and the two ADCs (ADC1 and ADC2) start converting the group of injected
channels. When the two ADCs finish the injected conversion, they resume the conversion of
the channel configured in interleaved mode.
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Note:
Dual modes
This application note is not delivered with a firmware example of this mode.
Figure 13. Dual combined: injected simultaneous + interleaved mode
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INJECTEDSIMULTANEOUS
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%NDOFINJECTEDCONVERSIONON!$#
AND!$#
!$#
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4RIGGERFORINJECTEDCHANNELS
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2.6.2
Example of application
You can use this dual combined mode in a UPS system (uninterruptible power supply). The
battery voltage is monitored with the ADC watchdog converted in dual interleaved mode.
The ADC also monitors the power consumed by the load by measuring the voltage and the
current in dual injected simultaneous mode.
Figure 14. UPS system
503
"ATTERYVOLTAGE
MONITORING
"ATTERIES
,OADVOLTAGEANDCURRENT
MEASUREMENTS
$#TO!#
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Conclusion
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Conclusion
This application note explains some ADC modes, and provides examples of applications to
make it easier to understand the presented modes. Most examples come with firmware to
simplify the ADC configuration and speed up development. With the provided firmware
examples, you can modify the code a little to switch from one mode to another.
The STM32’s ADC has several modes intended for advanced conversion processes so as to
attain efficient conversion results in applications such as motor control.
DMA is a major feature and its use is recommended when possible to avoid the loss of
samples and release the CPU load.
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Revision history
Revision history
Table 1.
Document revision history
Date
Revision
02-Mar-2010
1
Changes
Initial release.
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