How to change stm32 m4 adc channel?

On 4/28/21 9:36 PM, Ed Lee wrote:
> On Wednesday, April 28, 2021 at 4:41:06 PM UTC-7, Richard Damon wrote:
>> On 4/28/21 10:17 AM, Ed Lee wrote: 
>>> On Wednesday, April 28, 2021 at 1:17:13 AM UTC-7, Michael Kellett wrote: 
>>>> On 27/04/2021 21:50, Ed Lee wrote: 
>>>>> On Tuesday, April 27, 2021 at 9:33:12 AM UTC-7, Michael Kellett wrote: 
>>>>>> On 27/04/2021 16:39, Ed Lee wrote: 
>>>>>>> On Tuesday, April 27, 2021 at 5:35:04 AM UTC-7, Michael Kellett wrote: 
>>>>>>>> On 26/04/2021 18:25, Ed Lee wrote: 
>>>>>>>>> Does anyone know how to do it in register level? 
>>>>>>>>>
>>>>>>>>> I see many code examples using: 
>>>>>>>>>
>>>>>>>>> ADC_ChannelConfTypeDef sConfig = {ADC_CHANNEL_0, 1, ADC_SAMPLETIME_28CYCLES}; 
>>>>>>>>> HAL_ADC_ConfigChannel(&hadc1, &sConfig); 
>>>>>>>>> or 
>>>>>>>>> ADC_RegularChannelConfig(ADC1, ADC_channel_0, 1, ADC_SampleTime_480Cycles); 
>>>>>>>>>
>>>>>>>>> but i don't have access to these routines from arm-gcc. 
>>>>>>>>>
>>>>>>>>> By the way, i am using this to read the adc data: 
>>>>>>>>>
>>>>>>>>> #include "stm32f407xx.h" 
>>>>>>>>> ADC1->CR2 |= ADC_CR2_SWSTART; // Start A2D 
>>>>>>>>> while (!(ADC1->SR & ADC_SR_EOC)); // ready wait 
>>>>>>>>> data = ADC1->DR; 
>>>>>>>>>
>>>>>>>> If you download and install ST's Cube etc you will end up with (amongst 
>>>>>>>> a LOT of other stuff) the library code that you could use if you want 
>>>>>>>> functions like: 
>>>>>>>>
>>>>>>>> HAL_ADC_ConfigChannel() 
>>>>>>>>
>>>>>>>> I don't use these - they try to be universal but end up being hard to 
>>>>>>>> understand and slow. 
>>>>>>>>
>>>>>>>> To drive the ADC directly you will need to study the reference manual 
>>>>>>>> and register descriptions and it may well help to look at some ST 
>>>>>>>> examples (from the Cube again). 
>>>>>>>>
>>>>>>>> To address your specific problem: 
>>>>>>>>
>>>>>>>> Assuming a single conversion of one channel and starting after a 
>>>>>>>> hardware reset: 
>>>>>>>>
>>>>>>>> write the channel to be converted into the SQ1 field of ADC_SQR3 
>>>>>>>>
>>>>>>>> make sure the L field of ADC_SQR1 = 0 so the ADC does just one conversion 
>>>>>>>>
>>>>>>>> set the SMP field for the channel in question to the sampling time you 
>>>>>>>> want (ADC_SMPR1 or ADC_SMPR2) 
>>>>>>>>
>>>>>>>> enable the ADC by setting bit 0 in ADC_CR1 
>>>>>>>>
>>>>>>>> start the conversion by setting bit 30 in ADC_CR2 
>>>>>>>>
>>>>>>>> (All the above based on Ref manual for STM446xx - check details for your 
>>>>>>>> own processor.) 
>>>>>>>>
>>>>>>>> You will need to enable the ADC clock but you must have got there already. 
>>>>>>>>
>>>>>>>> MK 
>>>>>>>
>>>>>>> OK, i think this is getting close, but also need to select the Alt-Funct Reg for the port pin. I was hoping to find a complete example of such. 
>>>>>>>
>>>>>> You don't use the GPIO port Alt Function Register for making a pin an 
>>>>>> analogue input. 
>>>>>> You do it by setting the mode bits for that pin in the GPIO Mode register. 
>>>>>> There are two bits for each pin, coded like this: 
>>>>>>
>>>>>> Bits 2y:2y+1 MODERy[1:0]: Port x configuration bits (y = 0..15) 
>>>>>> These bits are written by software to configure the I/O direction mode. 
>>>>>> 00: Input (reset state) 
>>>>>> 01: General purpose output mode 
>>>>>> 10: Alternate function mode 
>>>>>> 11: Analog mode 
>>>>>>
>>>>>> I don't have any shareable examples that don't use DMA with scan and 
>>>>>> usually continuous mode for the ADC which I think might be distracting. 
>>>>>>
>>>>>> MK 
>>>>>
>>>>> So, reading from PA0 or PA1 like this? 
>>>>>
>>>>> RCC->APB2ENR |= RCC_APB2ENR_ADC1EN; // Enable ADC clock 
>>>>> ADC1->CR2 |= ADC_CR2_ADON; // Enable ADC 
>>>>> ADC1->SQR1 = 0; // bit 23-20 single coversion 
>>>>> ADC->SMPR2 = 2; // 28 cycles 
>>>>>
>>>>> #if PA0 
>>>>> GPIOA->MODER |= 3; // bit 1-0 Analog mode 
>>>>> ADC1->SQR3 = 0; // bit 3-0,0 channel 0 
>>>>> #endif 
>>>>>
>>>>> #if PA1 
>>>>> GPIOA->MODER |= 0xc; // bit 3-2 Analog mode 
>>>>> ADC1->SQR3 = 1; // bit 3-0,0 channel 1 
>>>>> #endif 
>>>>>
>>>>> ADC1->CR2 |= ADC_CR2_SWSTART; // Start ADC 
>>>>> while (!(ADC1->SR & ADC_SR_EOC)); // ready wait 
>>>>> DATA = ADC1->DR; // read data 
>>>>>
>>>> Not quite, entries in SMPR1/2 are for each ADC channel, not each entry 
>>>> in the sequencer. 
>>>> So for PA1 you need to set SMP1 bit field to 2, 
>>>> ADC->SMPR2 = (uint32_t)2 << 3; 
>>>
>>> OK, thanks. 
>>>
>>>> Here's a little challenge for you - good practice is to test this code 
>>>> - and that would mean you should test that the sampling time is actually 
>>>> what you meant it to be (not that you wrote x bits to y register). 
>>>> How would you do that ? 
>>>
>>> I guess i can measure the average conversion time from a sampling loop. For 100MHz clock, even 480 cycles are more than enough. 
>>>
>>> One question remain. How does it ties PA0 with channel 0? If it's hard coded, does it mean only port A can be analog? 
>>>
>> Each analog channel is hard tied internally to a given pin. (They are 
>> all port A from my memory, but scattered about a bit). Read the device 
>> reference manual for a listing of the capability of each pin.
> 
> OK, i will have dig a bit deeper in the reference manual.
> 
> This info is critical for someone like me new to the STM chip.
> 
> For the (microchip/Atmel) &mu;A SAM world, we have to set them explicitly.
> 
>         PORT->Group[1].DIRCLR.reg = PORT_PB09;
>         // Enable the peripheral multiplexer for PB09
>         PORT->Group[1].PINCFG[9].reg |= PORT_PINCFG_PMUXEN;
>         // Set PB09 to function B which is analog input.
>         PORT->Group[1].PMUX[4].reg = PORT_PMUX_PMUXO_B;
> 

The STM pins also have config registers to configure which special
function (if any) they are set for. There generally is a table listing
every pin and what functions it can connect to.