RP2350B: Working on Bidirectional bus using PIO at two different state machines (MicroPython 1.27.0) #19020
Replies: 3 comments 2 replies
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You're reading directly (a few ns) after toggling the direction, thus reading the inherent capacitance effects of those lines or pins. And – btw – what are the PIOs doing after they have been activated? Execute what ever is in the remaining parts of the 32 WORDS? You probably want some sort of a STOP command and a restart before using them again. |
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Hi @GitHubsSilverBullet , thanks for the help. I have spaced out the time (more than one second) between the read and the writes, however it is still giving me the last write. Also, I have made a mistake on the PIO - the SM should be in the loop waiting for the system to issue reads/writes. I have added the @rp2.asm_pio(out_init=(rp2.PIO.OUT_LOW,) * 16, out_shiftdir=rp2.PIO.SHIFT_RIGHT)
def write_data():
wrap_target()
mov(pindirs, ~null)
pull()
out(pins, 16)
wrap()
@rp2.asm_pio(out_init=(rp2.PIO.OUT_LOW,) * 16, in_shiftdir=rp2.PIO.SHIFT_LEFT)
def read_data():
wrap_target()
mov(pindirs, null)
in_(pins, 16)
push()
wrap()However, this still got stuck at the |
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There's a difference between wrap_target()
mov(pindirs, null) # change to input
in_(pins, 16) # read |
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Oooops, thanks for letting me know on this one. I had forgotten to insert these inside. I have checked and added some delays such as @rp2.asm_pio(out_init=(rp2.PIO.OUT_LOW,) * 16, out_shiftdir=rp2.PIO.SHIFT_RIGHT)
def write_data():
wrap_target()
mov(pindirs, invert(null))
nop()[31]
pull()
out(pins, 16)
wrap()
@rp2.asm_pio(out_init=(rp2.PIO.OUT_LOW,) * 16, in_shiftdir=rp2.PIO.SHIFT_LEFT)
def read_data():
wrap_target()
mov(pindirs, null)
nop()[31]
in_(pins, 16)
push()
wrap()
# more code there...
# SM1 for write data pins:
sm1_write_data = rp2.StateMachine(4, write_data, freq=10000, out_base=Pin(0))
sm1_write_data.active(1)
# SM2 for read data pins:
sm2_read_data = rp2.StateMachine(5, read_data, freq=10000, out_base=Pin(0))
sm2_read_data.active(1)
# some more code there too...
while True:
for i in range(10):
sm1_write_data.put(0xa5a5)
time.sleep(0.5)
print(f"sm2 read at {i}: {sm2_read_data.get():08X}")Unfortunately despite putting more than one |
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If you're toying with a High-impedance situation, keep in mind that there's still the Pad error in the A2 build of the 2350. In that case you want pull-down resistors, 8.2kΩ or less or High levels will get stuck . |
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Hello Micropython team,
I'm trying to perform a read and write on the same bus without accidentally reading the previous written value.
The issue seems to be if after I have written the bus (at "write enable") for example 0xA5A5, and then reading it back (at "write disable/Read enable") it gives me the last written value.
Here is the context: I'm writing a sample code for reading/writing on a S29GL Flash. The board and the NOR flash are already connected in a board I personally did.
I have split the writing of address and data on different state machine and different PIO too:
SM0 = address pins on GPIO16-39 @ PIO0
SM4 = write data pins on GPIO0-15 @ PIO1
SM5 = read data pins from GPIO0-15 @ PIO1
I was advised to change the
pindirswhen working on bidirectional pins. So I added thesemov(pindirs, null)andmov(pindirs,~null)accordingly in each of the state machine, read and write respectively.However, when switching to the inputs (
mov(pindirs,~null)) at reading the bus, it stalled after the first read. I'm not able to pinpoint whether I have left important command or setting beforehand.I'm a bit stuck here after searching all over the place for some similar attempts, so I appreciate any help. :D
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