I get STM32F103 DMA speed of 160 bytes in 1600 clock cycles => 1 transfer every 10 clock cycles. What else is contending the bus? Just seems a bit slow.

[Elektraglide]

This from a project I've been building color display output blogged here:

https://medium.com/@adambillyard/experiments-in-hard-realtime-35136ed79398

[waclawek.jan]

> The same code using TIM1 driving GPIO with PWM, has the same 72MHz timing as TIM3. Now I know! Is that explained anywhere?

Ah, the "timers clocked at twice the APB if APB is divided" gotcha.

 

Also, see Table 2 in RM0008. Btw, AFAIK this table is only in the 'F1 manuals.

> I think I need to configure the DMA to be DRQ-ed from the GPIO

There's no direct way to do this; you have to go through a channel of a timer set to input capture, triggering the DMA. And then you are probably better off simply triggering the DMA from a free-runnig timer. And I don't believe you'll achieve significantly higher transfer rate than what you see now.

JW