1 files changed, 44 insertions, 0 deletions
diff --git a/examples/rp2/pio_uart_tx.py b/examples/rp2/pio_uart_tx.py
new file mode 100644
index 000000000..0f8c1260b
--- /dev/null
+++ b/examples/rp2/pio_uart_tx.py
@@ -0,0 +1,44 @@
+# Example using PIO to create a UART TX interface
+
+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))