Error Transmitting data via UART when using ADC & DMA (works separately)

[ponuliukas]

Hi All,

I have been a little confused about my code and would appreciate some help greatly...

I have a basic program where I would like to read the ADC values from a sensor, and transmit them via UART for later signal processing and whatnot.

The structure is simple, and when I tested out reading the values from the ADC, as well as sending strings via UART - they both work perfectly fine. But now when I merge the two, the UART does not work anymore... I do not see anything in my serial monitor (Putty)

I feel like I am missing something big, but cannot find it. I would appreciate it if someone pointed me in the right direction :)

in my main, I have: 

 

 

uint32_t value[2]; // start adc in DMA mode
int isSent = 1;
uint8_t tx_buffer[] = "Welcome to BinaryUpdates!\n\r"; 

int main(void)
{
 HAL_Init();
 SystemClock_Config();
 MX_GPIO_Init();
 MX_DMA_Init();
 MX_ADC1_Init();
 MX_TIM3_Init();
 MX_TIM4_Init();
 MX_TIM2_Init();
 MX_USART6_UART_Init();

 HAL_ADC_Start_DMA(&hadc1, value, 2);

 while (1)
 {
	 if (isSent == 1)
	 {
	 	 HAL_UART_Transmit_DMA(&huart6, tx_buffer, 27);
// HAL_UART_Transmit_DMA(&huart6, value[0], sizeof(value[0]));
	 	 isSent = 0;
	 }
	 HAL_Delay(1000);
 }
}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
	isSent = 1;
}

 

 

[Andrew Neil]

---

@ponuliukas wrote:

the UART does not work anymore... 

---

What do you mean by that?

• It transmits nothing at all ?
• It transmits something, but not what you wanted ?
• other ?

 

EDIT:

You haven't shown your definition of isSent, but it should be 'volatile'

Do you have any conflicts between ADC and UART pins?

[ponuliukas]

Thank you for the reply @Andrew Neil and @raptorhal2 , and apologies for not being perfectly clear. I edited the question :) 

[Andrew Neil]

It's confusing to edit the question after people have already commented on the question in its original form!

It's better to post an update as a reply.

Again,  isSent should be 'volatile'

 

---

@ponuliukas wrote:

the UART does not work anymore... I do not see anything in my serial monitor (Putty) 

---

That could be because your UART is sending something that's not visible to PuTTY ?

Have you check on the wires with a logic analyser or oscilloscope?

You're ignoring the return value from HAL_UART_Transmit_DMA - it might be telling you something ...

https://community.st.com/t5/stm32-mcus-boards-and-hardware/hal-rcc-oscconfig/m-p/674455/highlight/true#M19028 

What happens if you do away with the DMA, and just use a plain blocking send?

[raptorhal2]

Edit: Cancel - I misunderstood. How do you get "value" into tx_buffer ?

[Andrew Neil]

---

@ponuliukas wrote:

 

 

uint8_t tx_buffer[27] = "Welcome to BinaryUpdates!\n\r"; 

 

 

---

Although it doesn't matter in the code you've shown so far, note that this does not leave space for a terminating NUL - so that won't be a proper C string.

To have a proper C string:

 

uint8_t tx_buffer[] = "Welcome to BinaryUpdates!\n\r";