Skip to main content
JLee.161
JLee.161
Associate III
October 10, 2019
Question

STM32L051K8 with timer triggered multiple ADC +USART (CubeMX + Keil) help needed:

Hello, I'm new to STM32 and I'm trying to use this MCU to do timer triggered multiple ADC sampling at 10Hz. I watched a few youtube guides on this matter which all use STM32F~ discovery boards, and have followed along, but got no good results so far.

I have set

1) enabled timer6 with update event every 100ms (baseclock 2.097mHz, prescaler 2097, counter period 100)

2) enabled ADC In 3-7

3) ADC_regular_conversionMode external trigger source timer6 trigger out event, trigger detection on rising edge

4) DMA continuous requests enabled

then in Keil:

1) uint16_t adcVar[5]

2) in main loop,

HAL_ADC_Start_DMA(&hadc, (uint32_t *)&adcVal, 5);

HAL_TIM_Base_Start(&htim6);

-----

Now I'm wondering how I could send each sample from each channel every 100ms through USART? I have tried using ADC interrupt to do so, but I can't get HAL_UART_Transmit to send the correct data.. any help please?

This topic has been closed for replies.

4 replies

TDK
TDK
October 11, 2019

What problem are you running into? What’s wrong with the data you’re trying to send?

i would probably use dma tx complete to start the uart transmission, but it could be done in many ways.

"If you feel a post has answered your question, please click ""Accept as Solution""."
JLee.161
JLee.161Author
Associate III
October 11, 2019

Hi, I'll outline my complete setup:

CubeMX:

Timer

TIM6 enabled, prescaler: 2097, counter:100, Trigger event: update event

ABP1 timer clock 2.097MHz

ADC

ADC IN3-7 enabled, DMA continuous requests enabled, EOC selection: end of sequence of conversion

sample time: 19.5cycles, external trigger source: timer6 trigger out, external trigger edge: trigger detection on rising edge

DMA mode circular peripheral-to-memory, data width: half word

DMA1 channel 1 interrupt enabled

ADC interrupt enabled

USART

USART1 enabled, USART_TX DMA enabled

DMA mode circular memory-to-peripheral, data width: byte

DMA1 channel 2 interrupt enabled

Keil:

variables

volatile uint16_t adcVal[5];

char header[10] = "AA";

while loop

 /* USER CODE BEGIN 2 */

HAL_ADC_Start_DMA(&hadc, (uint32_t *)&adcVal, 5);

HAL_TIM_Base_Start(&htim6);

 /* USER CODE END 2 */

ADC complete interrupt

HAL_UART_Transmit(&huart1, (uint8_t *)header, strlen(header), 10);

-------------------------------------

Soo it also seems that what was working yesterday isn't working anymore either (my 5 channel ADC values are not changing in debugging mode)...

What I wanted to do with the above ADC interrupt was to send the header variable first through USART, then send the five 16bit ADC data from channels 3-7 through USART as well...

So my question is:

1) Is there a reason my ADC isn't working anymore (seems like the interrupt stopped completely as well since not even the header is going through USART)? I've changed quite a bit of settings since yesterday and I'm not sure if I can return it to when it worked...

2) after ADC starts working and interrupt works, do I just have to do the following to send five 16bit data in ten 8bit data format?

HAL_UART_Transmit_DMA(&huart1, (uint8_t *)&adcVal, 10);

Thanks for the help, I really appreciate it as a beginner

Ozone
Ozone
Principal
October 11, 2019

> ADC complete interrupt

> HAL_UART_Transmit(&huart1, (uint8_t *)header, strlen(header), 10);

Do not send in an interrupt context.

Rather set a flag, and send from "normal" user context. You might need to copy the data before.

I hope you checked the output channel (serial interface) bandwidth can keep up with the input data (ADC value / strings).

JLee.161
JLee.161Author
Associate III
October 11, 2019

Hi Ozone, thanks for the reply. I actually tried the same code in the main while loop, but saw no avail (I received no data on the RX side). Could you tell me more what you mean by the bandwidth of the output channel? I just have the output of the USART connected to a CP2102 chip which I have always used to send 16bit data in 115200 baud rate. Thanks!

Terms & ConditionsAccessibility statement