SPI Mode 2 & 3 problems in sam0_common cpu #9695
Description
Description
SPI modes 2 & 3 have incorrect clock signals on samr21-xpro board or anything with the sam0_common cpu.
Steps to reproduce the issue
On the samr21-xpro run tests/periph_spi looking at PB22 and PB23
init 1 2 0 0 0
2018-08-03 13:40:14,532 - INFO # SPI_DEV(1) initialized: mode: 2, clk: 0, cs_port: 0, cs_pin: 0
> send UUUU
2018-08-03 13:40:18,405 - INFO # send UUUU
2018-08-03 13:40:18,406 - INFO # Sent bytes
2018-08-03 13:40:18,408 - INFO # 0 1 2 3
2018-08-03 13:40:18,410 - INFO # 0x55 0x55 0x55 0x55
2018-08-03 13:40:18,412 - INFO # U U U U
2018-08-03 13:40:18,413 - INFO #
2018-08-03 13:40:18,414 - INFO # Received bytes
2018-08-03 13:40:18,416 - INFO # 0 1 2 3
2018-08-03 13:40:18,418 - INFO # 0x00 0x00 0x00 0x00
2018-08-03 13:40:18,420 - INFO # ?? ?? ?? ??
If scoped you should see the above waveforms on the MOSI/SCK
Expected results
> Correct waveforms
This are the spected waveforms for each SPI mode (0 to 3), by changing the polarity and the phase.
| Mode | CPOL | CPHA |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 0 | 1 |
| 2 | 1 | 0 |
| 3 | 1 | 1 |
Actual results
> Mode 2
When SPI was configured in Mode 2 it was observed that SCK should be HIGH when the CS pin goes LOW (enabled) but it is LOW.
In this mode the falling edge should occur at the middle of the data pulse, but its happening at the beginning of it.
> Mode 3
In this case data sample should occur with the first rising edge of SCK and that should happen right in the middle of the data pulse. Instead, the rising edge of SCK occurs at the beginning of the data and at the middle there is a falling edge on SCK.
Versions
Operating system: Linux
Installed compiler toolchains
-----------------------------
native gcc: gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
arm-none-eabi-gcc: arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors 6-2017-q2-update) 6.3.1 20170620 (release) [ARM/embedded-6-branch revision 249437]
avr-gcc: missing
mips-mti-elf-gcc: missing
msp430-gcc: missing
riscv-none-embed-gcc: missing
clang: missing
Installed compiler libs
-----------------------
arm-none-eabi-newlib: "2.5.0"
mips-mti-elf-newlib: missing
riscv-none-embed-newlib: missing
avr-libc: missing (missing)
Installed development tools
---------------------------
cmake: missing
cppcheck: missing
doxygen: missing
flake8: missing
git: git version 2.17.1
coccinelle: missing