diff --git a/gateware/cal/cal.py b/gateware/cal/cal.py
index 6aeb3fe..0a1468a 100755
--- a/gateware/cal/cal.py
+++ b/gateware/cal/cal.py
@@ -80,10 +80,12 @@ def decode_raw_samples(n, raw, array_avg):
     ch_tc_values = np.zeros(n)
     while ix != n:
         channel = ix
-        msb = raw[ix*2]
-        lsb = raw[ix*2+1]
-        value = (msb << 8) | lsb
-        value_tc = twos_comp(value, 16)
+        byte0 = raw[ix*4]
+        byte1 = raw[ix*4+1]
+        byte2 = raw[ix*4+2]
+        byte3 = raw[ix*4+3]
+        value = (byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3
+        value_tc = twos_comp(value, 32)
         alpha = 0.3
         array_avg[channel] = alpha*value_tc + (1-alpha)*array_avg[channel]
         print(channel, hex(value), value_tc, int(array_avg[channel]))
diff --git a/gateware/cal/debug_uart.sv b/gateware/cal/debug_uart.sv
index 7d84fb2..7919cbb 100644
--- a/gateware/cal/debug_uart.sv
+++ b/gateware/cal/debug_uart.sv
@@ -9,6 +9,7 @@
 
 module debug_uart #(
     parameter W = 16, // sample width
+    parameter WM = 32, // maximum sample width
     parameter DIV = 12 // baud rate == CLK / DIV
 )(
     input clk,
@@ -32,6 +33,16 @@ logic [7:0] dout;
 logic tx1_ack;
 logic [7:0] state;
 
+logic signed [WM-1:0] adc0_ex;
+logic signed [WM-1:0] adc1_ex;
+logic signed [WM-1:0] adc2_ex;
+logic signed [WM-1:0] adc3_ex;
+
+assign adc0_ex = adc0;
+assign adc1_ex = adc1;
+assign adc2_ex = adc2;
+assign adc3_ex = adc3;
+
 uart_tx utx (
     .tx(tx_o),
     .data(dout),
@@ -50,26 +61,35 @@ always_ff @(posedge clk) begin
     end else if(tx1_ack) begin
         tx1_valid <= 1'b1;
         case (state)
-            0:  dout <= MAGIC1;
-            1:  dout <= MAGIC2;
-            2:  dout <= eeprom_mfg;
-            3:  dout <= eeprom_dev;
-            4:  dout <= eeprom_serial[31      :32-1*8];
-            5:  dout <= eeprom_serial[32-1*8-1:32-2*8];
-            6:  dout <= eeprom_serial[32-2*8-1:32-3*8];
-            7:  dout <= eeprom_serial[32-3*8-1:     0];
-            8:  dout <= jack;
-            // Note: we're currently only sending 2 bytes per
-            // sample for calibration purposes. This should
-            // eventually be derived from the sample width.
-            9:  dout <= 8'((adc0 & 16'hFF00) >> 8);
-            10: dout <= 8'((adc0 & 16'h00FF));
-            11: dout <= 8'((adc1 & 16'hFF00) >> 8);
-            12: dout <= 8'((adc1 & 16'h00FF));
-            13: dout <= 8'((adc2 & 16'hFF00) >> 8);
-            14: dout <= 8'((adc2 & 16'h00FF));
-            15: dout <= 8'((adc3 & 16'hFF00) >> 8);
-            16: dout <= 8'((adc3 & 16'h00FF));
+            0:   dout <= MAGIC1;
+            1:   dout <= MAGIC2;
+            2:   dout <= eeprom_mfg;
+            3:   dout <= eeprom_dev;
+            4:   dout <= eeprom_serial[32    -1:32-1*8];
+            5:   dout <= eeprom_serial[32-1*8-1:32-2*8];
+            6:   dout <= eeprom_serial[32-2*8-1:32-3*8];
+            7:   dout <= eeprom_serial[32-3*8-1:     0];
+            8:   dout <= jack;
+            // Channel 0
+            9:   dout <= adc0_ex[WM    -1:WM-1*8];
+            10:  dout <= adc0_ex[WM-1*8-1:WM-2*8];
+            11:  dout <= adc0_ex[WM-2*8-1:WM-3*8];
+            12:  dout <= adc0_ex[WM-3*8-1:     0];
+            // Channel 1
+            13:  dout <= adc1_ex[WM    -1:WM-1*8];
+            14:  dout <= adc1_ex[WM-1*8-1:WM-2*8];
+            15:  dout <= adc1_ex[WM-2*8-1:WM-3*8];
+            16:  dout <= adc1_ex[WM-3*8-1:     0];
+            // Channel 2
+            17:  dout <= adc2_ex[WM    -1:WM-1*8];
+            18:  dout <= adc2_ex[WM-1*8-1:WM-2*8];
+            19:  dout <= adc2_ex[WM-2*8-1:WM-3*8];
+            20:  dout <= adc2_ex[WM-3*8-1:     0];
+            // Channel 3
+            21:  dout <= adc3_ex[WM    -1:WM-1*8];
+            22:  dout <= adc3_ex[WM-1*8-1:WM-2*8];
+            23:  dout <= adc3_ex[WM-2*8-1:WM-3*8];
+            24:  dout <= adc3_ex[WM-3*8-1:     0];
             default: begin
                 // Should never get here
             end
diff --git a/gateware/eurorack_pmod.sv b/gateware/eurorack_pmod.sv
index 03e5849..7e6b84e 100644
--- a/gateware/eurorack_pmod.sv
+++ b/gateware/eurorack_pmod.sv
@@ -75,7 +75,7 @@ logic signed [W-1:0] sample_dac3;
 cal #(
     .W(W),
     .CAL_MEM_FILE(CAL_MEM_FILE)
-)cal_instance (
+) cal_instance (
     .rst(rst),
     .clk_256fs (clk_256fs),
     .clk_fs (clk_fs),
@@ -102,7 +102,9 @@ cal #(
 );
 
 // CODEC ser-/deserialiser. Sample rate derived from these clocks.
-ak4619 ak4619_instance (
+ak4619 #(
+    .W(W),
+) ak4619_instance (
     .rst       (rst),
     .clk_256fs (clk_256fs),
     .clk_fs    (clk_fs),
diff --git a/gateware/top.sv b/gateware/top.sv
index 45b1530..6a479e3 100644
--- a/gateware/top.sv
+++ b/gateware/top.sv
@@ -7,7 +7,7 @@
 //`define OUTPUT_CALIBRATION
 
 module top #(
-    parameter int W = 16 // sample width, bits
+    parameter int W = 32 // sample width, bits
 )(
 `ifndef INTERNAL_CLOCK
     input   CLK,
@@ -175,6 +175,7 @@ eurorack_pmod #(
 // Helper module to serialize some interesting state to a UART
 // for bringup and calibration purposes.
 debug_uart #(
+    .W(W),
     .DIV(12) // WARN: baud rate is determined by clk_256fs / 12 !!
 ) debug_uart_instance (
     .clk (clk_256fs),