rp2/rp2_pio: Add fifo_join support for PIO.

tjvr · dpgeorge · commit f842a40df4d2 · 2021-04-17T00:45:38.000+10:00
The PIO state machines on the RP2040 have 4 word deep TX and RX FIFOs. If you only need one direction, you can "merge" them into either a single 8 word deep TX or RX FIFO. We simply add constants to the PIO object, and set the appropriate bits in `shiftctrl`. Resolves adafruit#6854. Signed-off-by: Tim Radvan <tim@tjvr.org>
diff --git a/examples/rp2/pio_uart_rx.py b/examples/rp2/pio_uart_rx.py
@@ -22,6 +22,7 @@
     autopush=True,
     push_thresh=8,
     in_shiftdir=rp2.PIO.SHIFT_RIGHT,
+    fifo_join=PIO.JOIN_RX,
 )
 def uart_rx_mini():
     # fmt: off
diff --git a/ports/rp2/modules/rp2.py b/ports/rp2/modules/rp2.py
@@ -31,7 +31,8 @@ def __init__(
         autopush=False,
         autopull=False,
         push_thresh=32,
-        pull_thresh=32
+        pull_thresh=32,
+        fifo_join=0
     ):
         # uarray is a built-in module so importing it here won't require
         # scanning the filesystem.
@@ -40,7 +41,8 @@ def __init__(
         self.labels = {}
         execctrl = 0
         shiftctrl = (
-            (pull_thresh & 0x1F) << 25
+            fifo_join << 30
+            | (pull_thresh & 0x1F) << 25
             | (push_thresh & 0x1F) << 20
             | out_shiftdir << 19
             | in_shiftdir << 18
diff --git a/ports/rp2/rp2_pio.c b/ports/rp2/rp2_pio.c
@@ -360,6 +360,10 @@ STATIC const mp_rom_map_elem_t rp2_pio_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SHIFT_LEFT), MP_ROM_INT(0) },
     { MP_ROM_QSTR(MP_QSTR_SHIFT_RIGHT), MP_ROM_INT(1) },
 
+    { MP_ROM_QSTR(MP_QSTR_JOIN_NONE), MP_ROM_INT(0) },
+    { MP_ROM_QSTR(MP_QSTR_JOIN_TX), MP_ROM_INT(1) },
+    { MP_ROM_QSTR(MP_QSTR_JOIN_RX), MP_ROM_INT(2) },
+
     { MP_ROM_QSTR(MP_QSTR_IRQ_SM0), MP_ROM_INT(0x100) },
     { MP_ROM_QSTR(MP_QSTR_IRQ_SM1), MP_ROM_INT(0x200) },
     { MP_ROM_QSTR(MP_QSTR_IRQ_SM2), MP_ROM_INT(0x400) },

Original file line number	Diff line number	Diff line change
`@@ -22,6 +22,7 @@`
`22`	`22`	`autopush=True,`
`23`	`23`	`push_thresh=8,`
`24`	`24`	`in_shiftdir=rp2.PIO.SHIFT_RIGHT,`
	`25`	`+ fifo_join=PIO.JOIN_RX,`
`25`	`26`	`)`
`26`	`27`	`def uart_rx_mini():`
`27`	`28`	`# fmt: off`