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Port, board and/or hardware

PICO W

MicroPython version

MicroPython v1.22.2 on 2024-02-22; Raspberry Pi Pico W with RP2040

Problem

rp2.PIO(1).remove_program() removes all programs even the cyw43 program.

If after this statement a program is added to PIO(1) it is written from the TOP address 1F.
This cause the PICO to hang until unplugged.

CAUSE

If no program is given in rp2_pio_remove_program() then a program of lenth 32 and offset 0 is removed:

see rp2_pio_remove_program.c(314):

    uint8_t length = 32;
    uint offset = 0;
...
    struct pio_program pio_program = { NULL, length, -1 };
    rp2_pio_remove_managed_program(self->pio, &pio_program, offset);

This will also free the cyw43 pio program in the pico sdk, which keeps track of used memory.

SOLUTION

If no program is given in rp2.PIO(1).remove_program() the function should use

   rp2_pio_remove_all_managed_programs()

like it is used in rp2_pio_deinit().

This will only free instruction memory, that was allocated by python PIO. At least I hope. Didn't check this.

Steps to reproduce

# just some nop() instructions
program = [array('H', [41026, 41026, 41026, 41026, 41026]), -1, -1, 16384, 0, None, None, None]
print(program) 
rp2.StateMachine(7,program)
print(program)   # program is at address 21, because pio_add_program knows about used instruction memory
rp2.PIO(1).remove_program()
program[2] = -1 # not allocated yet, you could also use a new program
rp2.StateMachine(7,program)
print(program)   # now has offet 27 and overwrite cyw43 

this output is:

[array('H', [41026, 41026, 41026, 41026, 41026]), -1, -1, 16384, 0, None, None, None]
[array('H', [41026, 41026, 41026, 41026, 41026]), -1, 21, 16384, 0, None, None, None]
[array('H', [41026, 41026, 41026, 41026, 41026]), -1, 27, 16384, 0, None, None, None]

The program is, when added the second time, loaded at offset 27and overwrites the cyw43 program.

Workaround

instead of using remove_program() of PIO(1) use this code to free all memory except the cyw43 memory:
This assumes that cyw43 is loaded at address 1A to 1F (as it is in V1.22.2)

    nops = [array('H', [40993] * 26), -1, 0, 16384, 0, None, None, None] # mov(x,x)
    rp2.PIO(1).remove_program(nops)
    nops[2] = 0

Debug

To list the current instruction in pio memory, you can do this:

def Dump():
    from machine import mem32
    _SIZE_SM = const(0xe0 - 0xC8)
    smId = 2    
    end = 32
    start = 0 
    pio  = 1
    sm = rp2.PIO(1).state_machine(smId)        
    pioBase = 0x50200000+ pio * 0x100000
    
    smId = smId & 0x3
    for i in range(start,end,1):
        
        sm.exec(f"set(x,{i})")
        sm.exec(f"mov(pc,x)")
        addr = mem32[pioBase+smId*_SIZE_SM+ 0x0d4]
        instr = mem32[pioBase+smId*_SIZE_SM+0xD8]

        print(f"  {i:02X} {addr:04x}: {instr:04X} ")

this prints:

  00 0000: B598 
  01 0001: BBFB 
  02 0002: 304B 
  03 0003: AF57 
  04 0004: FA06 
  05 0005: 2FFD 
  06 0006: 3AF0 
  07 0007: CF3A 
  08 0008: CA27 
  09 0009: 54D9 
  0A 000a: ADA1 
  0B 000b: 8BA7 
  0C 000c: CEBE 
  0D 000d: FD26 
  0E 000e: EC7E 
  0F 000f: CBDF 
  10 0010: B147 
  11 0011: BA79 
  12 0012: 8ABF 
  13 0013: EF59 
  14 0014: 5D9A 
  15 0015: D7FA 
  16 0016: 6F9B 
  17 0017: EE48 
  18 0018: FF2A 
  19 0019: D58B 
  1A 001a: 6001
  1B 001b: 105A 
  1C 001c: E080 
  1D 001d: B042 
  1E 001e: 4001 
  1F 001f: 109E 

Address 1A to 1F is the CYW43 program

Cheers,
Dirk

Reproduction

just some nop() instructions
program = [array('H', [41026, 41026, 41026, 41026, 41026]), -1, -1, 16384, 0, None, None, None]
print(program)
rp2.StateMachine(7,program)
print(program) # program is at address 21, because pio_add_program knows about used instruction memory
rp2.PIO(1).remove_program()
program[2] = -1 # not allocated yet, you could also use a new program
rp2.StateMachine(7,program)
print(program) # now has offet 27 and overwrites cyw43

Expected behaviour

Don't overwrite cyw43 instructions.

Observed behaviour

cyw43 instructions are overwritten