How to use DAC1 Ch2 without dual mode Topic is solved

[neums]

Hello,
how i can use dac1 channel2 without dual mode. Due to manual it is possible to used this dac independently. In the dac_lld.c it seems that it is not possible with the current Version (code snip is part of dac_lld_start_conversion):

Code: Select all

  /* DAC configuration.*/
#if STM32_DAC_DUAL_MODE == FALSE
  cr = DAC_CR_DMAEN1 | (dacp->grpp->trigger << 3) | DAC_CR_TEN1 | DAC_CR_EN1;
  dacp->params->dac->CR &= dacp->params->regmask;
  dacp->params->dac->CR |= cr << dacp->params->regshift;
#else
  dacp->params->dac->CR = 0;
  cr = DAC_CR_DMAEN1 | (dacp->grpp->trigger << 3)  | DAC_CR_TEN1 | DAC_CR_EN1
                     | (dacp->grpp->trigger << 19) | DAC_CR_TEN2 | DAC_CR_EN2;
  dacp->params->dac->CR = cr;
#endif

It just used DAC1 Channel 2 if both are used and dual mode is activated. Is this correct?
The DMAEN2 bit is also not set.

Thank you for reply.

[Giovanni]

Hi,

Correct. the current driver does not support that scenario. Channel 2 is seen as part of DAC1 not as a separate DAC.

Giovanni

[neums]

Hi,
thank you for your answer. In the DACD2 handle definition in dac_lld.c (line 65 to 68) this scenario is declared but not implented in the driver function.

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/** @brief DAC1 CH2 driver identifier.*/
#if (STM32_DAC_USE_DAC1_CH2 && !STM32_DAC_DUAL_MODE) || defined(__DOXYGEN__)
DACDriver DACD2;
#endif

So if you define DAC1Ch2 in your mcuconf.h like this:

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#define STM32_DAC_DUAL_MODE                 FALSE
#define STM32_DAC_USE_DAC1_CH1              FALSE
#define STM32_DAC_USE_DAC1_CH2              TRUE

there will be a DAC2D handle which can not be used.

Is there a due date when the official driver will support this case? Dual Mode is not an opportunity for my Project because the PA4 (DAC1 Ch1) is used as ADC2IN1. Is there a work around to use both DAC1 channels in dual mode with the ADC2Ch1 working at PA4?

Thank you.

[Giovanni]

The idea is to complete the driver but I cannot give you an exact date, there is so much work in the pipeline (support for L0, L4 and F7 just talking of STM32).

Giovanni

[neums]

Hello,
when i use DAC1Ch1 and DAC1Ch2 without dual mode, then the channel 2 does not work. I fixed the problem in dac_lld.c void dac_lld_start_conversion(DACDriver *dacp) function as follows:
before fix:

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case DAC_DHRM_12BIT_RIGHT:
    osalDbgAssert(dacp->grpp->num_channels == 1, "invalid number of channels");

    dmaStreamSetPeripheral(dacp->params->dma, &dacp->params->dac->DHR12R1 +
                                              dacp->params->dataoffset);
    dmamode = dacp->params->dmamode |
              STM32_DMA_CR_PSIZE_HWORD | STM32_DMA_CR_MSIZE_HWORD;
    break;

after fix by casting the &dacp->params->dac->DHR12R1 pointer to uint32_t:

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case DAC_DHRM_12BIT_RIGHT:
    osalDbgAssert(dacp->grpp->num_channels == 1, "invalid number of channels");

    dmaStreamSetPeripheral(dacp->params->dma, (uint32_t)&dacp->params->dac->DHR12R1 +
                                              dacp->params->dataoffset);
    dmamode = dacp->params->dmamode |
              STM32_DMA_CR_PSIZE_HWORD | STM32_DMA_CR_MSIZE_HWORD;
    break;

The fault was that the address of the pointer was not correctly added with the dataoffset.

Can you check this scenario? Maybe i did something else wrong.

Thanks a lot.

[Giovanni]

It is a bug, thanks for finding.

Added a ticket: https://sourceforge.net/p/chibios/bugs/624/

Giovanni

[alex31]

Hello,

I am in the same position that a previous user, i want to use channel 2 alone in a design where channel 1 is already wired to
analog input.

in 2015/07 it was a work in progress, what is the status of the dac driver concerning that use case now ?

I have tried to use channel 2 alone, without dma, using dacPutChannelX (&DACD2, 0, VAL), but is does not seems to work.

Alexandre

[Giovanni]

Hi,

Please provide a (minimal) example I can test. The driver should allow to use channels individually.

Giovanni

[alex31]

I have made a minimal test, for discovery F4. there is 2 git branches inside :
° dac_channel_2 which show the problem
° dac_channel_1 which work

in the dac channel 1 branch, all is working as expected.
the voltmeter wired to PA4 shows around 0V during 5 seconds, then, when the led lit
the voltmeter shows around 3V.

in the dac channel 2 branch, the voltmeter wired to PA5 don't reflect the dac value, so something should go wrong
(i hope it's not in my code )

https://drive.google.com/file/d/0B3a7E0 ... sp=sharing

Alexandre

[alex31]

got it.

the problem is in dac_lld_put_channel function.
the dataoffset is not added in case of use of channel 2 only.
with the hal abstraction model, in case of only channel 2 used, the driver is DACD2 with only one channel (0),
but for the real hardware, the channel is channel 2 and offset has to be add.

adding the offset resolve the problem.

Code: Select all

void dac_lld_put_channel(DACDriver *dacp,
                         dacchannel_t channel,
                         dacsample_t sample) {

  switch (dacp->config->datamode) {
  case DAC_DHRM_12BIT_RIGHT:
#if STM32_DAC_DUAL_MODE
  case DAC_DHRM_12BIT_RIGHT_DUAL:
#endif
    if (channel == 0U) {
       dacp->params->dac->DHR12R1 =  (uint32_t)sample; // offset not taken into account
       *(&dacp->params->dac->DHR12R1 + dacp->params->dataoffset) = (uint32_t)sample; // proposal fix tested ok

of course, the offset has to be add for all the possible sample format, 12 bits RIGHT and LEFT, and 8 bits RIGHT.

Alexandre