Arduino for STM32

Posted: **Thu Jan 30, 2020 4:21 pm**

Im getting too higher ADC conversion time on the STM32F303CCT6 Black Pill Board, around 200-220 us

It can be some clock configurations?
There is any other function other than AnalogRead() that have a better conversion time?
There is some configuration of number of cycles for this reading?

Just for comparison, with STM32F103C8T6 i get about 65-68us of conversion time using the same code:

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float temp1 , temp2, temp3 = 0;
void setup()
{
  pinMode(PA0, INPUT);
  analogReadResolution(12);
  SerialUSB.begin();
 }
 
 void loop()
{

  temp1 = micros();

  temp3 = analogRead(PA0);

  temp2 = micros();

  SerialUSB.print(static_cast<double>(temp2 - temp1), 4);
  SerialUSB.println("us");

  delay(500);
}

This is my Platformio.ini:

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[env:robotdyn_blackpill_f303cc]
platform = ststm32
board = robotdyn_blackpill_f303cc
framework = arduino

Posted: **Thu Jan 30, 2020 5:36 pm**

ADC_SAMPLINGTIME and ADC_CLOCK_DIV could also be redefined by the variant or using build_opt.h.

See https://github.com/stm32duino/wiki/wiki ... l-channels

Posted: **Fri Jan 31, 2020 12:02 am**

fpiSTM wrote: Thu Jan 30, 2020 5:36 pm ADC_SAMPLINGTIME and ADC_CLOCK_DIV could also be redefined by the variant or using build_opt.h.

See https://github.com/stm32duino/wiki/wiki ... l-channels

as shown in the link, i added #include "stm32f3xx_ll_adc.h" and tried this two ways, but none of them worked:

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#if defined(STM32F3xx)
#define ADC_SAMPLINGTIME  LL_ADC_SAMPLINGTIME_19CYCLES_5
#define ADC_CLOCK_DIV LL_ADC_CLOCK_SYNC_PCLK_DIV2
#endif

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//added this line on setup()
LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_0, LL_ADC_SAMPLINGTIME_19CYCLES_5);

how can i change the sampling time and clock division?

Posted: **Fri Jan 31, 2020 7:13 am**

You go on the wrong way.
What I mean is ADC_SAMPLINGTIME can be redefined at sketch level. Do not use HAL or LL function as analogWrite do the full configuration.

Here how it is defined by default:
https://github.com/stm32duino/Arduino_C ... pp#L57-L71

And here the possible value for F3 series:
https://github.com/stm32duino/Arduino_C ... 1377-L1384

So, in our case the default value is :

ADC_SAMPLETIME_13CYCLES_5

To redefine int you can create a build_opt.h file and define the desired value:

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-DADC_SAMPLINGTIME=ADC_SAMPLETIME_1CYCLE_5

Or add hal_conf_extra.h with:

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#define ADC_SAMPLINGTIME ADC_SAMPLETIME_1CYCLE_5

This is the same for

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ADC_CLOCK_DIV

Anyway, analogRead() do a full configuration each time it is called. The fact you get a lesser time on a STM32F103 is not really relevant as it is not the same series nor the same HAL ADC.

Posted: **Fri Jan 31, 2020 12:09 pm**

fpiSTM wrote: Fri Jan 31, 2020 7:13 am
To redefine int you can create a build_opt.h file and define the desired value:
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-DADC_SAMPLINGTIME=ADC_SAMPLETIME_1CYCLE_5

I tried to creat a file called build_opt.h with the line you suggested and added #include "build_opt.h", but i get the following error:

In file included from src\main.cpp:3:0:
src\build_opt.h:1:1: error: expected unqualified-id before '-' token
-DADC_SAMPLINGTIME=ADC_SAMPLETIME_1CYCLE_5
^
*** [.pio\build\robotdyn_blackpill_f303cc\src\main.cpp.o] Error 1

Then i tried to include this lines in Platformio.ini:

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build_flags = 
    -D ADC_SAMPLINGTIME=ADC_SAMPLETIME_1CYCLE_5
    -D ADC_CLOCK_DIV=ADC_CLOCK_SYNC_PCLK_DIV1

The sketch compiled but nothing changed

For last i created the file hal_conf_extra.h with this lines and added #include "hal_conf_extra.h":

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#define ADC_SAMPLINGTIME ADC_SAMPLETIME_1CYCLE_5
#define ADC_CLOCK_DIV ADC_CLOCK_SYNC_PCLK_DIV4

The sketch compiles too, i tried to play with the clock divider and sampling time, but nothing changed again

I want to have 12 bit resolution at the adc, so i have analogReadResolution(12) at the setup(), this can mess with the other configurations?

Do you recommend any sampling and clock configuration for the best 12bit readings with the lower time conversion?

Sorry to ask so many questions, im new to platformio

Posted: **Fri Jan 31, 2020 1:50 pm**

I didn't support PIO as I do not use it.

leogomide07 wrote: Fri Jan 31, 2020 12:09 pm I tried to creat a file called build_opt.h with the line you suggested and added #include "build_opt.h", but i get the following error:

I never told to include it, just create it, it is a dedicated file for the GCC option... See the Wiki.
Same for the hal_conf_extra.h , this is managed dynamically.

As It told analogRead is not for high performance ADC. You could crosscheck the clock settings maybe the ADC clock can be increased.

One other way, you can use the HAL or LL and even use the DMA but you will have to do this on your own.
I've provided an example how to use HAL on the code snipplets:
viewtopic.php?f=41&t=110

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