DMA interrupt in STM32F407

[parthiban]

Posted on June 08, 2015 at 15:01

Hi,

Am trying Quadrature sampling in STM32F407 controller. DMA interrupt is happening in every 1.5ms, after filtering the values, 256 bits of data(one packet) will get ready in every 480ms. This was working fine. But when i enable the USART NVIC, the timing of the packet increases, that is its happening now in every 760ms. Moreover am not transmitting or receiving any data via USART. But still the timing get increased just by enabling the NVIC of USART. Am not sure what could be the issue. Am i missing something in the USART initialization. Please help me on this. Thank you in advance.

[Tesla DeLorean]

Posted on June 08, 2015 at 15:21

Yeah, I'm not able to understand your problem from your description. Perhaps you could present a concise example that demonstrates the problem, and explain the buffer size and trigger mechanism for the DMA.

If you enable interrupts you need to service them properly. With the USART TXE interrupt you have to supply data to the USART to clear it, or disable the interrupt source.