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7 years, 9 months ago.
timeline for Serial or SPI async on ST Micro M4?
Anyone have any idea when async Serial might be supported on ST Micro processors? In particular I am using an STM32F446 (Arm Cortex M4). I could *really* use it. Same goes for async SPI.
Basically, I need to run an AnalogOut @ 100 KHz without any time jitter and send some UART and SPI messages concurrently. I tried the mbed RTOS but it seems to always swap threads every 5 ms no matter how I play with osPriority and/or calling Thread::yield().
Thanks!
Elwood Downey Steward Observatory University of Arizona
1 Answer
7 years, 9 months ago.
Hi Elwood,
In mbed OS 3 we have async SPI and async serial, which I know works (as I have used it :-)). According to the docs there should be async SPI etc. in mbed OS 5.1 as well (see DEVICE_SPI_ASYNCH). If you see thread swapping happening every 5 ms. that'd be a bug, so please file it here.
Hi Jan, thanks much for your response.
I was not very clear. When I called the Serial async methods read() and write() I would get a compile error "Platform not compatible with Low Power APIs for Serial". But no worries, I found Sam Grove's BufferedSerial and it solves my problem.
Regarding Thread granularity, it was my error in thinking. I had two threads and main() was sitting in wait(10000). I was assuming things worked like POSIX threads where this would not be schedulable, but now I understand it is in mbed. So now I just have one thread, with the other work directly in main(). The two each call yield() and bounce back and forth nicely.
Best regards,
Elwood
posted by 10 Aug 2016