Read 18bits from SPI?

RE: Read 18bits from SPI?

awneil — Fri, 05 Aug 2016 13:45:57 GMT

Because (by definition) the master always generates the clock, the number of bits sent by the master (on MOSI) always has to be the same as the number of bits received (on MISO).

RE: Read 18bits from SPI?

bx — Fri, 05 Aug 2016 13:17:02 GMT

awneil is right, SPI does not necessarily work with bytes, and the specific ADC I am interfacing outputs 18bit, period. Is there any other way to define the amount of data to be rx, other than setting tx string of specific lenght?

RE: Read 18bits from SPI?

awneil — Fri, 05 Aug 2016 11:30:00 GMT

Err - the thing with SPI (unlike I2C, say) is that there is no standard for this stuff!

The only thing that SPI defines is the 4 wires - it says absolutely nothing about numbers of bits or anything else to do with higher-level protocols.

So the question is actually about the specific peripheral implementation in the particular chip (nRF51422) - and has nothing to do with SPI itself.

en.wikipedia.org/.../Serial_Peripheral_Interface_Bus

RE: Read 18bits from SPI?

Øyvind Karlsen — Fri, 05 Aug 2016 11:10:57 GMT

Hi,

SPI normally uses entire bytes, so it makes sense to receive 8, 16 24, 32 bits etc in each section.

If everything is working for you I think it's better to follow the standard and focus on keeping your code well commented for easy review.

Best regards,

Øyvind