softwareserial on nrf52

RE: softwareserial on nrf52

Stas — Wed, 08 Nov 2017 16:21:16 GMT

Mostly we need only 9600 baudrate. But It seems best decision is to use additional chip e.g. stm32f205 has 4 usart, 2 uart.

RE: softwareserial on nrf52

Hung Bui — Wed, 08 Nov 2017 16:02:44 GMT

Yes, but I was thinking of high UART baudrate , says 115200bps, the CPU has to wake up every 8us. Also since the 4 UART is not syncronized, you need to sample twice as fast as the clock to make sure you won't miss any pulse. Another limitation is if you have higher priority interrupt (softdevice activity for example) you will miss some bytes on UART.

RE: softwareserial on nrf52

Stas — Tue, 07 Nov 2017 19:13:29 GMT

CPU to read pins only on timer interrupt. All time after interrupt CPU in WFI state.

RE: softwareserial on nrf52

Hung Bui — Tue, 07 Nov 2017 16:39:03 GMT

How exactly did you implement your soft serial ? My understanding is to use high frequency timer, and use CPU to read the pin on every pulse of the timer, to detect the start bit , stop bit and the data. And on each pulse of the timer the CPU read all 4 pins a the same time, so it doesn't matter if you have 4 UART or more.

It's mor like a parallel port, but in this case you have only 4 bit, and start bit and stop bit has to be handled.

But this solution requires the CPU to stay in the timer event handle most of the time. So what you are thinking of using external UART chip maybe a better solution.

RE: softwareserial on nrf52

Stas — Tue, 07 Nov 2017 11:28:42 GMT

The problem is we can not manage handler from different instances of one timer simultaneously. We can work only with one softserial uart at a time. When the packets coincide our library is fail. So we wonder could freertos solve this problem. We gonna use hardware uart too of course. We tend to use additional chip stm32f205ret6 it has 6 uart modules 51 GPIO and a lot of other peripherals, on the board we gonna connect it by spi with our main chip nrf52832.

RE: softwareserial on nrf52

Hung Bui — Tue, 07 Nov 2017 10:11:30 GMT

Hi Stas,

Could you explain a little bit more what is the problem when you mentioned "some conflicts in timer handlers" ?

Could you provide some more information why you can't use the hardware UART on the nRF52 ? At least it would reduce the number of bit banging UART to 3