How to read ADC for different ADC pins using DMA buffer?

[Tejashree]

I am have configured 3 ADC pins (PA4,PC4,PB11) with DMA.I want to read individual values at 3 different PINs.

how do adjust the size of the buffer for 3 Pins?Or any other way to read it?

[KnarfB]

The ADC values are interleaved in the buffer. So multiply the buffer size by the number of channels. The last parameter in HAL_ADC_Start_DMA is the size in Bytes. So 17 seems odd. Use sizeof(adc_buf) or calculate by *sizeof(uint32_t) etc..

If unsure: heavily oversize the allocated buffer, fill it with 0 and validate that only the expected number of bytes/values is written by debugging/dumping the buffer.

hth

KnarfB

[Tejashree]

 HAL_ADC_Start_DMA(&hadc2, (uint32_t*)adc_buf, sizeofbuf);

Here I tried sizeofbuf as 3.But I cannot read the value .

Can you help me to set the exact value for sizeofbuf.

I am using ADC2.

PA4-ADC2_IN17

PC4-ADC2_IN5

PB11-ADC2_IN14

these are pins used.

What sizeofbuf should i choose in this case?

[Tejashree]

 HAL_ADC_Start_DMA(&hadc2, (uint32_t*)adc_buf, sizeofbuf);

Here I tried sizeofbuf as 3.But I cannot read the value .

Can you help me to set the exact value for sizeofbuf.

I am using ADC2.

PA4-ADC2_IN17

PC4-ADC2_IN5

PB11-ADC2_IN14

these are pins used.

What sizeofbuf should i choose in this case?

[Javier1]

Did you checked DMA init was called before ADC_init?

Its a common bug in cumemx autogenerated code

it happened to me

[Tejashree]

Yes, DMA_Init() is called before ADC_Init().

[Javier1]

could you post an image of your cubeMX setup for the ADCs?

you should be able to calculate sizeofbuf with that info

match your receiving buffer unit definition (uint8_t/uint16_t/uint32_t) to the one setup n your DMA

word=32bits

halfword=16bits

byte=8bits

[Tejashree]

Half Word = 16 bits

so what would be my buffer size for following Pins?

PA4-ADC2_IN17

PC4-ADC2_IN5

PB11-ADC2_IN14

[ssipa.1]

hello

you can read the following tutorial

STM32 ADC Read Example - DMA / Interrupt / Polling Example Code (deepbluembedded.com)

[MM..1]

simply how many samples you need in buffer for one pin X num pins

for you for example 100 x 3 = 300

uint16_t adc_buf[300];
 
 HAL_ADC_Start_DMA(&hadc2, (uint32_t*)adc_buf,300);

but your images is chaos DMA show ADC1 instead ADC2 and checked inputs isnt as you write