Strange Behaviour HAL_TIM_PWM_Start_DMA

[Simi_Myr]

Hello everyone.
I am encountering a very strange issue with the STM32H7B0 using the J-Link to debug.
I followed this tutorial to control the WS28B12 LED using Timer, PWM and DMA.
I use the following function to transmit the PWM data. 

if (HAL_TIM_PWM_Start_DMA(&htim1, TIM_CHANNEL_1, address, 74) != HAL_OK) Error_Handler();

 But here comes the strange thing:

If i run the code, nothing happens, or lets say, the data doesn't get transmitted:

But if i look at value of the address variable in the debugger before running the ...Start_DMA...:

And then Resume the program it suddenly works:

Why does this happen?
Any help is appreciated

[Sarra.S · Accepted solution]

Hello @Simi_Myr, 

The behavior that you're describing, where the program works after inspecting the variable in the debugger, means that there might be a timing issue or a need for a delay! This is probably related to the debug mode settings.

Try adding  a breakpoint in your callback function to monitor the execution flow and ensure that the source data has been transferred to the destination buffer 

[TDK]

> the data doesn't get transmitted

Looks like your code sets everything to 0, or at least most of it (50/74 values) but we can't see the rest. The data looks like a bunch of 0's being transmitted.