SPI 32 bits per word errors

[sjkelly]

Thank you for this package, it has been very helpful for interactive debugging in the REPL!

I am trying to set the bits_per_word parameter and receiving a few errors in the IOCtl.

julia> using BaremetalPi

julia> init_spi("/dev/spidev0.0", max_speed_hz = 100_000, mode=0x00, bits_per_word=32)
ERROR: Could not open `/dev/spidev0.0`. Make sure you have the required permissions.
Stacktrace:
 [1] error(::String) at ./error.jl:33
 [2] init_spi(::Array{String,1}; mode::UInt8, max_speed_hz::Int64, bits_per_word::Int64) at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/spi.jl:93
 [3] #init_spi#1 at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/spi.jl:35 [inlined]
 [4] top-level scope at REPL[2]:1
caused by [exception 1]
SystemError: Error in IOCTL call: Invalid argument
Stacktrace:
 [1] _ioctl(::Int64, ::UInt64, ::Base.RefValue{Int64}) at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/ioctl.jl:20
 [2] _ioctl at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/ioctl.jl:10 [inlined]
 [3] init_spi(::Array{String,1}; mode::UInt8, max_speed_hz::Int64, bits_per_word::Int64) at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/spi.jl:82
 [4] #init_spi#1 at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/spi.jl:35 [inlined]
 [5] top-level scope at REPL[2]:1

julia> init_spi("/dev/spidev0.0", max_speed_hz = 100_000, mode=0x00)

julia> a = [zero(UInt32)]
1-element Array{UInt32,1}:
 0x00000000

julia> spi_transfer!(1, [0x00000001], a, bits_per_word=32)
ERROR: SystemError: Error in IOCTL call: Invalid argument
Stacktrace:
 [1] _ioctl at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/ioctl.jl:20 [inlined]
 [2] spi_transfer!(::Int64, ::Array{UInt32,1}, ::Array{UInt32,1}; max_speed_hz::Int64, delay_usecs::Int64, bits_per_word::Int64, cs_change::Bool) at /home/ubuntu/.julia/packages/BaremetalPi/vlIDG/src/spi.jl:298
 [3] top-level scope at REPL[11]:1

It is possible I have something wrong or a missing driver. This is on the Ras pi 4 with 64 bit ubuntu 20.04. It works fine with 8 bit words.

[ronisbr]

Hi @sjkelly

Thank you for this package, it has been very helpful for interactive debugging in the REPL!

Nice! I am glad it is being useful.

I am trying to set the bits_per_word parameter and receiving a few errors in the IOCtl.

I think you found a bug. Can you please test if this work passing a Int8 or UInt8 to the keyword bits_per_word:

julia> init_spi("/dev/spidev0.0", max_speed_hz = 100_000, mode=0x00, bits_per_word=Int8(32))

julia> init_spi("/dev/spidev0.0", max_speed_hz = 100_000, mode=0x00, bits_per_word=UInt8(32))

[sjkelly]

I tried both, and still get the same error. FWIW the permission error is just default. I tried changing this line to UInt8 with no avail either:

BaremetalPi.jl/src/spi.jl

Line 56 in 5e658e7

bits_per_word = [bits_per_word for _ = 1:num_init_devices]

It is possible the Ras Pi does not support 32 bit per word send, as the error occurs setting the SPI_IOC_WR_BITS_PER_WORD. If not, the error should probably be at the ioctl call like here:

https://github.com/cpb-/spi-tools/blob/4a36a84f7df291ddaebd397aecf0c8515256a8e0/src/spi-config.c#L231-L236

I am setting up a python test to verify real quick if it is hardware or otherwise.

[ronisbr]

It is possible the Ras Pi does not support 32 bit per word send, as the error occurs setting the SPI_IOC_WR_BITS_PER_WORD. If not, the error should probably be at the ioctl call like here:

https://github.com/cpb-/spi-tools/blob/4a36a84f7df291ddaebd397aecf0c8515256a8e0/src/spi-config.c#L231-L236

Yes, the IOCTL is failing due to an invalid argument. Initially, I thought it could be the format of the variable bits_per_word, which would be solved by my proposal. Now, it can be that the hardware does not support 32 bits per word. If you can check with python and tell me, I will appreciate!

[sjkelly]

Yes, It seems to be the hardware:

>>> import spidev
>>> spi = spidev.SpiDev()
>>> spi.open(0,0)
>>> spi.max_speed_hz
125000000
>>> spi.max_speed_hz = 100000
>>> spi.mode
0
>>> spi.bits_per_word
8
>>> spi.bits_per_word = 0x20
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 22] Invalid argument
>>> spi.bits_per_word
8

I also validated with spi-tools and it does not support 32 bit words.

This is also confirmed in the docs: https://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md

Thanks for the help!

[ronisbr]

Nice! Thanks for the info :) This is important to me because I only have the Pi Zero to test. Knowing that it is working in another device is really nice!