pio_encode_mov(pio_pindirs, pio_x) gives wrong value

[PetteriAimonen]

When calling:

pio_encode_mov(pio_pindirs, pio_x);

it returns 0xA081, while according to datasheet the correct value would be 0xA061

I think this is a left-over bug from RP2040 which doesn't support pindirs as mov destination.

[lurch]

I did a bit of digging, and it looks like you're right.

I compiled these tables of encoding bit-patterns from the PIO chapters of the RP2040 and RP2350 datasheets: (with bold highlighting where RP2350 differs from RP2040)

Chip	Instruction	Src or Dest	00	01	10	11
RP2040	WAIT	Source	GPIO	PIN	IRQ	Reserved
RP2350	WAIT	Source	GPIO	PIN	IRQ	JMPPIN

Chip	Instruction	Src or Dest	000	001	010	011	100	101	110	111
RP2040	IN	Source	PINS	X	Y	NULL	Reserved	Reserved	ISR	OSR
RP2040	OUT	Destination	PINS	X	Y	NULL	PINDIRS	PC	ISR	EXEC
RP2040	MOV	Destination	PINS	X	Y	Reserved	EXEC	PC	ISR	OSR
RP2040	MOV	Source	PINS	X	Y	NULL	Reserved	STATUS	ISR	OSR
RP2040	SET	Destination	PINS	X	Y	Reserved	PINDIRS	Reserved	Reserved	Reserved
RP2350	IN	Source	PINS	X	Y	NULL	Reserved	Reserved	ISR	OSR
RP2350	OUT	Destination	PINS	X	Y	NULL	PINDIRS	PC	ISR	EXEC
RP2350	MOV	Destination	PINS	X	Y	PINDIRS	EXEC	PC	ISR	OSR
RP2350	MOV	Source	PINS	X	Y	NULL	Reserved	STATUS	ISR	OSR
RP2350	SET	Destination	PINS	X	Y	Reserved	PINDIRS	Reserved	Reserved	Reserved

pio_encode_mov(enum pio_src_dest dest, enum pio_src_dest src) just does

return _pio_encode_instr_and_src_dest(pio_instr_bits_mov, dest, src & 7u);

pio_src_dest is defined as:

enum pio_src_dest {
    pio_pins = 0u,
    pio_x = 1u,
    pio_y = 2u,
    pio_null = 3u | _PIO_INVALID_SET_DEST | _PIO_INVALID_MOV_DEST,
    pio_pindirs = 4u | _PIO_INVALID_IN_SRC | _PIO_INVALID_MOV_SRC | _PIO_INVALID_MOV_DEST,
    pio_exec_mov = 4u | _PIO_INVALID_IN_SRC | _PIO_INVALID_OUT_DEST | _PIO_INVALID_SET_DEST | _PIO_INVALID_MOV_SRC,
    pio_status = 5u | _PIO_INVALID_IN_SRC | _PIO_INVALID_OUT_DEST | _PIO_INVALID_SET_DEST | _PIO_INVALID_MOV_DEST,
    pio_pc = 5u | _PIO_INVALID_IN_SRC | _PIO_INVALID_SET_DEST | _PIO_INVALID_MOV_SRC,
    pio_isr = 6u | _PIO_INVALID_SET_DEST,
    pio_osr = 7u | _PIO_INVALID_OUT_DEST | _PIO_INVALID_SET_DEST,
    pio_exec_out = 7u | _PIO_INVALID_IN_SRC | _PIO_INVALID_SET_DEST | _PIO_INVALID_MOV_SRC | _PIO_INVALID_MOV_DEST,
};

which explains why pio_encode_mov(pio_pindirs, pio_x); is encoding pio_pindirs as binary 100 instead of the binary 011 that the MOV instruction in RP2350's PIO expects.

So perhaps pio_src_dest needs to be tweaked to add:

#if PICO_PIO_VERSION > 0
    pio_pindirs_mov = 3u _PIO_INVALID_IN_SRC | _PIO_INVALID_OUT_DEST | _PIO_INVALID_SET_DEST | _PIO_INVALID_MOV_SRC,
#endif

and then your example-code would need to do pio_encode_mov(pio_pindirs_mov, pio_x); instead of pio_encode_mov(pio_pindirs, pio_x);.