Photon Test Breakout Board

[rickkas7]

I was unable to get a single byte SPI.transfer(c) to work for a SPI slave. The example in this post does 8 byte transfers, but you can simply make the data buffer smaller and it will transfer fewer bytes.

SPI2.transfer(tx_buffer, rx_buffer, sizeof(rx_buffer), NULL); gives me hardware error

I think you’re getting a hard fault on the SPI slave device because you have a Particle.publish in your onSelect handler. The onSelect is an interrupt handler and you can’t call Particle.publish in it. I wouldn’t even recommend calling Serial.print. You should only set the select_state flag. As far as I can tell, you can’t use a single byte SPI transfer in SPI slave mode. I never get valid data doing that. You need to use the multi-byte DMA transfer mode. I prefer to structure my code differen…