SPI_Master : Expecting same result in SPI Mode 0 and 3 but it differs

[muhkuhns]

In the sensor datasheet it says one can use SPI_Mode 0 or 3 (doesn't say that there is anything to do to switch between them).

I connected MISO from the DK with SDO from the Sensor and MOSI with SDI

I tried all 4 CPHA/CPOL combinations and 2 should give me the same result.. but they all differ! (Of course I chose a coefficient that should be constant (and with no change in spi mode but just resetting to get the result again it is.).

RX from left to right: reset-command, prom-read-command 0xA6, prom read results

ActiveLow + Trailing : FE FE 92 93 
ActiveLow + Leading : FF FF C9 49 
ActiveHigh + Leading : FE FE FE C8 
ActiveHigh + Trailing : FF FE FE 87

What am I missing? I used the ble_uart example and added SPI. Of course I tried other speeds too.

Maybe someone with a 100% working SPI Slave could flash, just edit the command and test if the code works?

main.c ble_app_uart.zip

Datasheet of Sensor

[Stian Røed Hafskjold]

ActiveLow + Leading and ActiveHigh + Trailing should give you the same results. Could it be that the last bit you receive is some kind of ACK bit, and that if you receive 0xFF it was not acknowledged. And the two other modes give you a false 0xFE because SDO is sampled to late. Problems like this is really hard to debug without a logic analyzer. It could be many things..