diff --git a/src/main/io/serial.c b/src/main/io/serial.c
index 901f14d2d2..2765cfb575 100644
--- a/src/main/io/serial.c
+++ b/src/main/io/serial.c
@@ -36,6 +36,9 @@
 #include "drivers/serial_uart.h"
 #endif
 
+#include "drivers/gpio.h"
+#include "drivers/light_led.h"
+ 
 #if defined(USE_VCP)
 #include "drivers/serial_usb_vcp.h"
 #endif
@@ -92,7 +95,7 @@ baudRate_e lookupBaudRateIndex(uint32_t baudRate)
     return BAUD_AUTO;
 }
 
-static serialPortUsage_t *findSerialPortUsageByIdentifier(serialPortIdentifier_e identifier)
+serialPortUsage_t *findSerialPortUsageByIdentifier(serialPortIdentifier_e identifier)
 {
     uint8_t index;
     for (index = 0; index < SERIAL_PORT_COUNT; index++) {
@@ -421,3 +424,55 @@ void evaluateOtherData(serialPort_t *serialPort, uint8_t receivedChar)
         systemResetToBootloader();
     }
 }
+
+#if defined(GPS) || ! defined(SKIP_SERIAL_PASSTHROUGH)
+// Default data consumer for serialPassThrough.
+static void nopConsumer(uint8_t data)
+{
+    UNUSED(data);
+}
+
+/*
+ A high-level serial passthrough implementation. Used by cli to start an
+ arbitrary serial passthrough "proxy". Optional callbacks can be given to allow
+ for specialized data processing.
+ */
+void serialPassthrough(serialPort_t *left, serialPort_t *right, serialConsumer 
+                       *leftC, serialConsumer *rightC)
+{
+    waitForSerialPortToFinishTransmitting(left);
+    waitForSerialPortToFinishTransmitting(right);
+
+    if (!leftC)
+        leftC = &nopConsumer;
+    if (!rightC)
+        rightC = &nopConsumer;
+
+    LED0_OFF;
+    LED1_OFF;
+
+    // Either port might be open in a mode other than MODE_RXTX. We rely on
+    // serialRxBytesWaiting() to do the right thing for a TX only port. No
+    // special handling is necessary OR performed.
+    while(1) {
+        // TODO: maintain a timestamp of last data received. Use this to
+        // implement a guard interval and check for `+++` as an escape sequence
+        // to return to CLI command mode.
+        // https://en.wikipedia.org/wiki/Escape_sequence#Modem_control
+        if (serialRxBytesWaiting(left)) {
+            LED0_ON;
+            uint8_t c = serialRead(left);
+            serialWrite(right, c);
+            leftC(c);
+            LED0_OFF;
+         }
+         if (serialRxBytesWaiting(right)) {
+             LED0_ON;
+             uint8_t c = serialRead(right);
+             serialWrite(left, c);
+             rightC(c);
+             LED0_OFF;
+         }
+     }
+ }
+ #endif