1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
# Example using PIO to create a UART TX interface
# ruff: noqa: F821 - @asm_pio decorator adds names to function scope
from machine import Pin
from rp2 import PIO, StateMachine, asm_pio
UART_BAUD = 115200
PIN_BASE = 10
NUM_UARTS = 8
@asm_pio(sideset_init=PIO.OUT_HIGH, out_init=PIO.OUT_HIGH, out_shiftdir=PIO.SHIFT_RIGHT)
def uart_tx():
# fmt: off
# Block with TX deasserted until data available
pull()
# Initialise bit counter, assert start bit for 8 cycles
set(x, 7) .side(0) [7]
# Shift out 8 data bits, 8 execution cycles per bit
label("bitloop")
out(pins, 1) [6]
jmp(x_dec, "bitloop")
# Assert stop bit for 8 cycles total (incl 1 for pull())
nop() .side(1) [6]
# fmt: on
# Now we add 8 UART TXs, on pins 10 to 17. Use the same baud rate for all of them.
uarts = []
for i in range(NUM_UARTS):
sm = StateMachine(
i, uart_tx, freq=8 * UART_BAUD, sideset_base=Pin(PIN_BASE + i), out_base=Pin(PIN_BASE + i)
)
sm.active(1)
uarts.append(sm)
# We can print characters from each UART by pushing them to the TX FIFO
def pio_uart_print(sm, s):
for c in s:
sm.put(ord(c))
# Print a different message from each UART
for i, u in enumerate(uarts):
pio_uart_print(u, "Hello from UART {}!\n".format(i))
|
