SPI MOSI default high? NRF SDK 12.2.0

RE: SPI MOSI default high? NRF SDK 12.2.0

MattyIce — Thu, 17 Aug 2017 16:32:38 GMT

It turns out my issue was due to the full-duplex nature of the SPI driver. Namely, for every byte sent on the MOSI line, a byte is received on the MISO line. So if you send 4 bytes and want to read one byte, in response, you need to make the rx buffer 5 bytes long and read the 5th byte as the "response" from the slave.

RE: SPI MOSI default high? NRF SDK 12.2.0

Nick Bentzen — Thu, 17 Aug 2017 12:24:14 GMT

I was not able to solve this problem - I did end up electrically inverting the MOSI signal (and flipped bits in code to compensate) and it didn't solve my problem - turns out it was EMI.

RE: SPI MOSI default high? NRF SDK 12.2.0

Jørn — Thu, 17 Aug 2017 08:42:56 GMT

Unfortunately setting the MOSI pin high will not change the pins polarity between transmissions. The SPI hardware takes control of the pin, and it will keep the pin low between transmissions. After the SPI is uninitialized the pin will maintain its configuration (low) until the application changes this. The only way I can think of to achieve a high MOSI pin between transmissions is to unititialize the SPI between every transmission and "manually" set the pin high.

RE: SPI MOSI default high? NRF SDK 12.2.0

MattyIce — Tue, 15 Aug 2017 16:40:06 GMT

@Turbo J, where is that change made?

RE: SPI MOSI default high? NRF SDK 12.2.0

Turbo J — Tue, 20 Jun 2017 22:42:03 GMT

Try setting the corresponding bit to 1in NRF_GPIO->OUTregister.