It all works!!! I think- need to make sure I copied the code oever right.

Author: efairbanks

libraries/I2S/src/pio_i2s.pio

@@ -141,15 +141,15 @@ lastbit:             ; Last bit toggles WCLK to mark frame boundary
 ; to be 32 (as per the TDM specs)
 ;                           +----- WCLK
 ;                           |+---- BCLK
-    mov x, y         side 0b01 [1]
+    mov x, y         side 0b00 [1]
 bitloop:
-    in pins, 1       side 0b00    ; Sample input on falling edge
-    out pins, 1      side 0b00    ; Output changes on falling edge
-    jmp x-- bitloop  side 0b01 [1]
+    out pins, 1      side 0b11    ; Output changes on falling edge
+    in pins, 1       side 0b11    ; Sample input on falling edge
+    jmp x-- bitloop  side 0b00 [1]
 
 lastbit:             ; Last bit toggles WCLK to mark frame boundary
-    in pins, 1       side 0b10
-    out pins, 1      side 0b10
+    in pins, 1       side 0b01
+    out pins, 1      side 0b01
     ; Loop back to the beginning
 
 .program pio_tdm_inout_swap
@@ -529,9 +529,6 @@ static inline void pio_tdm_inout_program_init(PIO pio, uint sm, uint offset, uin
         pio_sm_exec(pio, sm, pio_encode_set(pio_y, bits * channels - 2));
     }
 
-    // Initialize input shift register
-    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, 32));  // Shift in first TDM frame
-    
     // Need to make OSR believe there's nothing left to shift out
     pio_sm_exec(pio, sm, pio_encode_out(pio_osr, 32));
 }

libraries/I2S/src/pio_i2s.pio.h

@@ -267,12 +267,12 @@ static inline pio_sm_config pio_tdm_in_swap_program_get_default_config(uint offs
 
 static const uint16_t pio_tdm_inout_program_instructions[] = {
             //     .wrap_target
-    0xa922, //  0: mov    x, y            side 1 [1] 
-    0x4001, //  1: in     pins, 1         side 0     
-    0x6001, //  2: out    pins, 1         side 0     
-    0x0941, //  3: jmp    x--, 1          side 1 [1] 
-    0x5001, //  4: in     pins, 1         side 2     
-    0x7001, //  5: out    pins, 1         side 2     
+    0xa122, //  0: mov    x, y            side 0 [1] 
+    0x7801, //  1: out    pins, 1         side 3     
+    0x5801, //  2: in     pins, 1         side 3     
+    0x0141, //  3: jmp    x--, 1          side 0 [1] 
+    0x4801, //  4: in     pins, 1         side 1     
+    0x6801, //  5: out    pins, 1         side 1     
             //     .wrap
 };
 
@@ -737,10 +737,8 @@ static inline void pio_tdm_inout_program_init(PIO pio, uint sm, uint offset, uin
         pio_sm_exec(pio, sm, pio_encode_pull(false, false));
         pio_sm_exec(pio, sm, pio_encode_mov(pio_y, pio_osr));
     } else {
-        pio_sm_exec(pio, sm, pio_encode_set(pio_y, bits * channels - 1));
+        pio_sm_exec(pio, sm, pio_encode_set(pio_y, bits * channels - 2));
     }
-    // Initialize input shift register
-    pio_sm_exec(pio, sm, pio_encode_in(pio_pins, 32));  // Shift in first TDM frame
     // Need to make OSR believe there's nothing left to shift out
     pio_sm_exec(pio, sm, pio_encode_out(pio_osr, 32));
 }