Avoid swapping L/R channels on I2S input (#2124)

earlephilhower · web-flow · commit a8e663477632 · 2024-04-25T11:22:07.000-07:00
Fixes #2123
diff --git a/libraries/I2S/src/pio_i2s.pio b/libraries/I2S/src/pio_i2s.pio
@@ -295,8 +295,8 @@ static inline void pio_i2s_in_program_init(PIO pio, uint sm, uint offset, uint d
 
     pio_sm_exec(pio, sm, pio_encode_set(pio_y, bits - 2));
 
-    // Offset the data by 1 bit
-    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1));
+    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits)); // Shift in 1st L data
+    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1)); // Shift in 1st R data modulo one bit, avoiding bit shift from #2037
 }
 
 %}
diff --git a/libraries/I2S/src/pio_i2s.pio.h b/libraries/I2S/src/pio_i2s.pio.h
@@ -378,8 +378,8 @@ static inline void pio_i2s_in_program_init(PIO pio, uint sm, uint offset, uint d
     pio_sm_set_pindirs_with_mask(pio, sm, pin_mask, pin_mask);
     pio_sm_set_pins(pio, sm, 0); // clear pins
     pio_sm_exec(pio, sm, pio_encode_set(pio_y, bits - 2));
-    // Offset the data by 1 bit
-    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1));
+    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits)); // Shift in 1st L data
+    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1)); // Shift in 1st R data modulo one bit, avoiding bit shift from #2037
 }
 
 #endif

Original file line number	Diff line number	Diff line change
`@@ -295,8 +295,8 @@ static inline void pio_i2s_in_program_init(PIO pio, uint sm, uint offset, uint d`
`295`	`295`
`296`	`296`	`pio_sm_exec(pio, sm, pio_encode_set(pio_y, bits - 2));`
`297`	`297`
`298`		`- // Offset the data by 1 bit`
`299`		`- pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1));`
	`298`	`+ pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits)); // Shift in 1st L data`
	`299`	`+ pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1)); // Shift in 1st R data modulo one bit, avoiding bit shift from #2037`
`300`	`300`	`}`
`301`	`301`
`302`	`302`	`%}`