#I am trying to implement a PIO program

1 messages · Page 1 of 1 (latest)

acoustic kiln
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The error I am currently getting is:

ValueError: Invalid set destination 'bits'
subtle sable
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you don't have variables

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you have two registers for that, x and y

acoustic kiln
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ah

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Alright, code now fixed to:

.program rs485
.side_set 1 opt
loop:
    set x, 31              ; A variable used to keep track of how many bits we have gone through
    out y, 32              ; Shove 32 bits from the shift register into the register `y`
bitloop:                   ; This is where we will loop back to until all bits are written out
    out pins, y side 1     ; Set the pin high based on `y` to write out
    jmp x-- bitloop side 0 ; Keep looping while bits has not performed 32 times
complete:
    jmp loop               ; Loop back to the beginning where we will wait for more data to write

I am now getting ValueError: invalid syntax for integer with base 10. Does it not like 31 or 32?

subtle sable
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I think it doesn't like the "y" in out pins, y side 1

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you can't use registers in place of numbers

acoustic kiln
subtle sable
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the out instruction takes the destination and the count, and count has to be a constant, not a register

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look at page 323 of the datasheet, it lists all possible variants of the out instruction

acoustic kiln
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Ok, after reading the actual documentation for OUT, I think I have a better understanding for the operation.

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I think that I should change this around so that I pull for 32 bits (a word for the protocol) then just shift out from the OSR for each bit remaining in the OSR.

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I think that should work

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Maybe?

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.program rs485
.side_set 1 opt
loop:
    pull 32                ; Ensure we have 32 bits to shift out
    set x, 31              ; A variable used to keep track of how many bits we have gone through
bitloop:                   ; This is where we will loop back to until all bits are written out
    out pins, 1 side 1     ; Set the pin high based on `y` to write out
    jmp x-- bitloop side 0 ; Keep looping while bits has not performed 32 times
complete:
    jmp loop               ; Loop back to the beginning where we will wait for more data to write
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Also:

  1. I am not sure what .side_set 1 opt does or if I need it.
  2. the side 0 and side 1 I am trying to use to pull the second pin to be high or low in that instruction. Hopefully that is what that actually does
subtle sable
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.side_set 1 opt tells it that for each instruction there may be optionally a sideset instruction that sets one pin to the specified value

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the way you wrote it, you will have the pin set to 1 for one instruction, and to 0 for 5 instructions

acoustic kiln
subtle sable
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you can set a different set of pins for side and for out

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oh, and you can change value or direction

acoustic kiln
acoustic kiln
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This is the current progress on what my program looks like. The yellow line is the data line and the blue line is effectively a clock. The timing for everything looks amazing.

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However, the data I am sending is not accurate. It looks like it is looping on a the first byte pulled from the shift register.

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I am trying to write out: A000FF00 as a test. What is actually represented is 32 bits of A0 then 32 bits of 00, then 32 bits of FF. Where the byte is written four times.

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So I guess when I pull 32, this does not pull 32 bits, but rather 8 bits? And just loops over that byte when I try to write too much from the 8 bits pulled?

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The program is:

.program rs485
.side_set 1 opt
loop:
    set x, 31              ; A variable used to keep track of how many bits we have gone through
    pull 32                ; Ensure we have 32 bits to shift out
bitloop:                   ; This is where we will loop back to until all bits are written out
    out pins, 1     side 1 ; Set the pin high based on `y` to write out
    jmp x-- bitloop side 0 ; Keep looping while bits has not performed 32 times
complete:
    jmp loop               ; Loop back to the beginning where we will wait for more data to write
#

And this is the corresponding state machine:

sm = rp2pio.StateMachine(
    arinc_write,
    frequency=200000,
    first_out_pin=board.D12,
    out_pin_count=1,
    first_sideset_pin=board.D13,
    sideset_pin_count=1,
    sideset_enable=True,
    out_shift_right=False,  # Start pulling out most sigificant bits first
    auto_pull=True,
    pull_threshold=32,  # Make sure we can pull 32 bits
)