[BUG] spi_xfer Currently Fails

[TheCedarPrince]

Hi @Alexander-Barth and co,

Just wanted to report that while #18 did work to open a SPI interface, it now appears I am unable to write with SPI. Here's code in Python (using your tip about checking out the Python library):

import pigpio

pi = pigpio.pi()

SPI_CHANNEL = 0  # SPI channel (0 or 1)
SPI_SPEED = 1000000  # SPI speed in Hz (1 MHz)
SPI_FLAGS = 0  # SPI flags (0 for default)

handle = pi.spi_open(SPI_CHANNEL, SPI_SPEED, SPI_FLAGS)
data_to_send = [0x01, 0x02, 0x03, 0x04]  # Example data
count, data_received = pi.spi_xfer(handle, data_to_send)

And the output

>>> handle
0 # Or 1 -- this is correct to the Julia version

>>> count
4

>>> data_received
bytearray(b'\x00\x00\x00\x00')

Here's the same version in Julia:

julia> using PiGPIO

julia> p = Pi();
[ Info: Successfully connected!

julia> h = PiGPIO.spi_open(p, 1, 100000, 0)
0

julia> data_to_send = [0x01, 0x02, 0x03, 0x04]
4-element Vector{UInt8}:
 0x01
 0x02
 0x03
 0x04


julia> count, data = PiGPIO.spi_xfer(p, h, data_to_send)
ERROR: UndefVarError: `u2i` not defined
Stacktrace:
 [1] spi_xfer(self::Pi, handle::Int32, data::Vector{UInt8})
   @ PiGPIO ~/.julia/packages/PiGPIO/UOeJH/src/spiSerial.jl:199
 [2] top-level scope
   @ REPL[5]:1

I then tried to patch it with the following fix:

julia> function spi_xfer(self::Pi, handle, data)
           # I p1 handle
           # I p2 0
           # I p3 len
           ## extension ##
           # s len data bytes

           # Don't raise exception.  Must release lock.
           bytes = signed(PiGPIO._pigpio_command_ext(
           self.sl, PiGPIO._PI_CMD_SPIX, handle, 0, length(data), data, false))
           if bytes > 0
               data = PiGPIO.rxbuf(bytes)
           else
               data = ""
           end
           unlock(self.sl.l)
           return bytes, data
       end
spi_xfer (generic function with 1 method)

julia> (count, data) = spi_xfer(p, h, data_to_send)
(0, "")

But that doesn't return what the Python version did. Any thoughts about how to fix this @Alexander-Barth or @aviks? I can examine the Python version a bit more, but was curious what your thought is here first.

Cheers!

~ tcp 🌳

[Alexander-Barth]

I just made a couple of commits, but I don't think that they address the root issue here.
When you rerun your code with:

ENV["JULIA_DEBUG"] = "PiGPIO"

Can you copy the screen output here? It would be useful to compare them to also some internal calls in pigpio.py (the python functions spi_xfer, _pigpio_command_ext_nolock,...). This, however, would require to change also the python code to some print calls there.

[TheCedarPrince]

Hey @Alexander-Barth, seems like we are moving a little bit further along! Here is what I am seeing:

julia> ENV["JULIA_DEBUG"] = "PiGPIO"
"PiGPIO"

julia> using PiGPIO

julia> p = Pi()
┌ Debug: _pigpio_command
│   out =
│    16-element Vector{UInt8}:
│     0x63
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
└ @ PiGPIO ~/.julia/packages/PiGPIO/I3q1H/src/pi.jl:111
[ Info: Successfully connected!
Pi("localhost", 8888, true, PiGPIO.SockLock(Sockets.TCPSocket(RawFD(17) open, 0 bytes waiting), ReentrantLock(nothing, 0x00000000, 0x00, Base.GenericCondition{Base.Threads.SpinLock}(Base.IntrusiveLinkedList{Task}(nothing, nothing), Base.Threads.SpinLock(0)), (0, 0, 0))), PiGPIO.CallbackThread(PiGPIO.SockLock(Sockets.TCPSocket(RawFD(17) open, 0 bytes waiting), ReentrantLock(nothing, 0x00000000, 0x00, Base.GenericCondition{Base.Threads.SpinLock}(Base.IntrusiveLinkedList{Task}(nothing, nothing), Base.Threads.SpinLock(0)), (0, 0, 0))), PiGPIO.SockLock(Sockets.TCPSocket(RawFD(18) paused, 0 bytes waiting), ReentrantLock(nothing, 0x00000000, 0x00, Base.GenericCondition{Base.Threads.SpinLock}(Base.IntrusiveLinkedList{Task}(nothing, nothing), Base.Threads.SpinLock(0)), (0, 0, 0))), true, true, 0, 0x00000000, Any[]))

julia> h = PiGPIO.spi_open(p, 0, 100000, 0)
┌ Debug: _pigpio_command_ext
│   out =
│    16-element Vector{UInt8}:
│     0x47
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│        ⋮
│     0x01
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│   ext =
│    20-element Vector{UInt8}:
│     0x47
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│        ⋮
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
└ @ PiGPIO ~/.julia/packages/PiGPIO/I3q1H/src/pi.jl:137
0

julia> data_to_send = [0x01, 0x02, 0x03, 0x04]
4-element Vector{UInt8}:
 0x01
 0x02
 0x03
 0x04

julia> count, data = PiGPIO.spi_xfer(p, h, data_to_send)
┌ Debug: _pigpio_command_ext
│   out =
│    16-element Vector{UInt8}:
│     0x4b
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│        ⋮
│     0x00
│     0x00
│     0x04
│     0x00
│     0x00
│     0x00
│   ext =
│    20-element Vector{UInt8}:
│     0x4b
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│        ⋮
│     0x00
│     0x00
│     0x01
│     0x02
│     0x03
│     0x04
└ @ PiGPIO ~/.julia/packages/PiGPIO/I3q1H/src/pi.jl:137
ERROR: UndefVarError: `readbytes` not defined
Stacktrace:
 [1] rxbuf(self::Pi, count::Int32)
   @ PiGPIO ~/.julia/packages/PiGPIO/I3q1H/src/pi.jl:354
 [2] spi_xfer(self::Pi, handle::Int32, data::Vector{UInt8})
   @ PiGPIO ~/.julia/packages/PiGPIO/I3q1H/src/spiSerial.jl:205
 [3] top-level scope
   @ REPL[8]:1

Here I'll note that it does appear like the ext array does receive the byte data. But I am not sure how to access it. However, I did a small patch to the rxbuf and spi_xfer functions as follows:

julia> function rxbuf(self::Pi, count)
           ext = readbytes!(self.sl.s, count, all)
           return ext
       end
rxbuf (generic function with 1 method)

julia> function spi_xfer(self::Pi, handle, data)
           # I p1 handle
           # I p2 0
           # I p3 len
           ## extension ##
           # s len data bytes

           # Don't raise exception.  Must release lock.
           bytes = PiGPIO.u2i(PiGPIO._pigpio_command_ext(
           self.sl, PiGPIO._PI_CMD_SPIX, handle, 0, length(data), data, false))
           if bytes > 0
               data = rxbuf(self, bytes)
           else
               data = ""
           end
           unlock(self.sl.l)
           return bytes, data
       end
spi_xfer (generic function with 1 method)

julia> (count, data) = spi_xfer(p, 1, data_to_send)
┌ Debug: _pigpio_command_ext
│   out =
│    16-element Vector{UInt8}:
│     0x00
│     0x00
│     0x00
│     0x00
│     0x4b
│     0x00
│        ⋮
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│     0x00
│   ext =
│    20-element Vector{UInt8}:
│     0x4b
│     0x00
│     0x00
│     0x00
│     0x01
│     0x00
│        ⋮
│     0x00
│     0x00
│     0x01
│     0x02
│     0x03
│     0x04
└ @ PiGPIO ~/.julia/packages/PiGPIO/I3q1H/src/pi.jl:137
(0, "")

But it still does not return what the Python code does. I can try a fork of the pigpio python package as well and adding in some debug statements while I tinker if that would be helpful @Alexander-Barth. Otherwise, any other thoughts?

Thanks!

[Alexander-Barth]

Yes the rxbuf function is incorrect. Can you try with the following?

function rxbuf(self::Pi, count)
    ext = read(self.sl.s, count)
    return ext
end

In general, when we hit some error state, we might need to make a new connection to the pigpio deamon (a new Pi object). Maybe it is even necessary to restart the deamon (sudo systemctl restart pigpiod).

[TheCedarPrince]

Good news @Alexander-Barth ! This seems to work now!

I get exactly what I was expecting based on the Python version. I opened a PR with the fix here: #21

I'll let you close the issue in case you had any more questions. Otherwise, back to tinkering!

[Alexander-Barth]

This is great, thank you for all your tests!