diff --git a/esp-link/cgipins.c b/esp-link/cgipins.c
index b763d12..bf4754d 100644
--- a/esp-link/cgipins.c
+++ b/esp-link/cgipins.c
@@ -32,9 +32,10 @@ int ICACHE_FLASH_ATTR cgiPinsGet(HttpdConnData *connData) {
   int len;
 
   len = os_sprintf(buff,
-      "{ \"reset\":%d, \"isp\":%d, \"conn\":%d, \"ser\":%d, \"swap\":%d, \"rxpup\":%d }",
+      "{ \"reset\":%d, \"isp\":%d, \"conn\":%d, \"ser\":%d, \"swap\":%d, \"rxpup\":%d, \"txen\":%d }",
       flashConfig.reset_pin, flashConfig.isp_pin, flashConfig.conn_led_pin,
-      flashConfig.ser_led_pin, !!flashConfig.swap_uart, !!flashConfig.rx_pullup);
+      flashConfig.ser_led_pin, !!flashConfig.swap_uart, !!flashConfig.rx_pullup,
+      flashConfig.tx_enable_pin);
 
   jsonHeader(connData, 200);
   httpdSend(connData, buff, len);
@@ -48,7 +49,7 @@ int ICACHE_FLASH_ATTR cgiPinsSet(HttpdConnData *connData) {
   }
 
   int8_t ok = 0;
-  int8_t reset, isp, conn, ser;
+  int8_t reset, isp, conn, ser, tx_enable;
   uint8_t swap, rxpup;
   ok |= getInt8Arg(connData, "reset", &reset);
   ok |= getInt8Arg(connData, "isp", &isp);
@@ -56,6 +57,7 @@ int ICACHE_FLASH_ATTR cgiPinsSet(HttpdConnData *connData) {
   ok |= getInt8Arg(connData, "ser", &ser);
   ok |= getBoolArg(connData, "swap", &swap);
   ok |= getBoolArg(connData, "rxpup", &rxpup);
+  ok |= getInt8Arg(connData, "txen", &tx_enable);
   if (ok < 0) return HTTPD_CGI_DONE;
 
   char *coll;
@@ -75,6 +77,10 @@ int ICACHE_FLASH_ATTR cgiPinsSet(HttpdConnData *connData) {
       if (pins & (1<<ser)) { coll = "Serial LED"; goto collision; }
       pins |= 1 << ser;
     }
+    if (tx_enable >= 0) {
+        if (pins & (1<<tx_enable)) { coll = "TX Enable"; goto collision; }
+        pins |= 1 << tx_enable;
+    }
     if (swap) {
       if (pins & (1<<15)) { coll = "Uart TX"; goto collision; }
       if (pins & (1<<13)) { coll = "Uart RX"; goto collision; }
@@ -90,8 +96,9 @@ int ICACHE_FLASH_ATTR cgiPinsSet(HttpdConnData *connData) {
     flashConfig.ser_led_pin = ser;
     flashConfig.swap_uart = swap;
     flashConfig.rx_pullup = rxpup;
-    os_printf("Pins changed: reset=%d isp=%d conn=%d ser=%d swap=%d rx-pup=%d\n",
-	reset, isp, conn, ser, swap, rxpup);
+    flashConfig.tx_enable_pin = tx_enable;
+    os_printf("Pins changed: reset=%d isp=%d conn=%d ser=%d swap=%d rx-pup=%d tx_enable=%d\n",
+	reset, isp, conn, ser, swap, rxpup, tx_enable);
 
     // apply the changes
     serbridgeInitPins();
diff --git a/esp-link/config.c b/esp-link/config.c
index 224f047..e3a4fe7 100644
--- a/esp-link/config.c
+++ b/esp-link/config.c
@@ -34,6 +34,7 @@ FlashConfig flashDefault = {
   .data_bits	= EIGHT_BITS,
   .parity	= NONE_BITS,
   .stop_bits	= ONE_STOP_BIT,
+  .tx_enable_pin = -1,
 };
 
 typedef union {
@@ -160,6 +161,13 @@ bool ICACHE_FLASH_ATTR configRestore(void) {
       flashConfig.parity = flashDefault.parity;
       flashConfig.stop_bits = flashDefault.stop_bits;
   }
+  if (flashConfig.tx_enable_pin == 0 &&
+      (flashConfig.conn_led_pin == 0 || flashConfig.reset_pin == 0 ||
+       flashConfig.isp_pin == 0 || flashConfig.ser_led_pin == 0)) {
+    // just added tx_enable_pin and it got the default 0, which is not good, need to default to
+    // disabled.
+    flashConfig.tx_enable_pin = -1;
+  }
   return true;
 }
 
diff --git a/esp-link/config.h b/esp-link/config.h
index 65195d2..862bf0c 100644
--- a/esp-link/config.h
+++ b/esp-link/config.h
@@ -41,6 +41,7 @@ typedef struct {
   int8_t   data_bits;
   int8_t   parity;
   int8_t   stop_bits;
+  int8_t   tx_enable_pin;
 } FlashConfig;
 extern FlashConfig flashConfig;
 
diff --git a/esp-link/main.c b/esp-link/main.c
index 88cc705..8d5d015 100644
--- a/esp-link/main.c
+++ b/esp-link/main.c
@@ -163,10 +163,11 @@ void ICACHE_FLASH_ATTR
 user_init(void) {
   system_timer_reinit();
 
-// uncomment the following three lines to see flash config messages for troubleshooting
+  // uncomment the following three lines to see flash config messages for troubleshooting
   //uart_init(115200, 115200);
   //logInit();
-  //os_delay_us(100000L);
+  //os_delay_us(60000L);
+
   // get the flash config so we know how to init things
   //configWipe(); // uncomment to reset the config for testing purposes
   bool restoreOk = configRestore();
diff --git a/html/home.html b/html/home.html
index de9862f..59dc5fd 100644
--- a/html/home.html
+++ b/html/home.html
@@ -76,6 +76,12 @@
                   <div class="popup">Second signal to program &#xb5;C.
                     AVR:not used, esp8266:gpio2, ARM:ISP</div>
                 </div>
+                <div class="pure-control-group">
+                  <label for="pin-txen">TX Enable</label>
+                  <select id="pin-txen"></select>
+                  <div class="popup">A pin that should be asserted high while transmitting
+                    (eg. to put RS/485 trancievers into TX mode)</div>
+                </div>
                 <div class="pure-control-group">
                   <label for="pin-conn">Conn LED</label>
                   <select id="pin-conn"></select>
diff --git a/html/ui.js b/html/ui.js
index 67361c9..eb50b4c 100644
--- a/html/ui.js
+++ b/html/ui.js
@@ -393,12 +393,12 @@ function showNotification(text) {
 //===== GPIO Pin mux card
 
 var pinPresets = {
-  // array: reset, isp, conn, ser, swap, rxpup
-  "esp-01":       [  0, -1, 2, -1, 0, 1 ],
-  "esp-12":       [ 12, 14, 0,  2, 0, 1 ],
-  "esp-12 swap":  [  1,  3, 0,  2, 1, 1 ],
-  "esp-bridge":   [ 12, 13, 0, 14, 0, 0 ],
-  "wifi-link-12": [  1,  3, 0,  2, 1, 0 ],
+  // array: reset, isp, conn, ser, swap, rxpup, txen
+  "esp-01":       [  0, -1, 2, -1, 0, 1, -1 ],
+  "esp-12":       [ 12, 14, 0,  2, 0, 1, -1 ],
+  "esp-12 swap":  [  1,  3, 0,  2, 1, 1, -1 ],
+  "esp-bridge":   [ 12, 13, 0, 14, 0, 0, -1 ],
+  "wifi-link-12": [  1,  3, 0,  2, 1, 0, -1 ],
 };
 
 function createPresets(sel) {
@@ -418,6 +418,7 @@ function createPresets(sel) {
     setPP("ser",   pp[3]);
     setPP("swap",  pp[4]);
     $("#pin-rxpup").checked = !!pp[5];
+    setPP("txen",  pp[6]);
     sel.value = 0;
   };
 
@@ -453,6 +454,7 @@ function displayPins(resp) {
   createSelectForPin("ser", resp["ser"]);
   $("#pin-swap").value = resp["swap"];
   $("#pin-rxpup").checked = !!resp["rxpup"];
+  createSelectForPin("txen", resp["txen"]);
   createPresets($("#pin-preset"));
 
   $("#pin-spinner").setAttribute("hidden", "");
@@ -469,7 +471,7 @@ function setPins(ev) {
   ev.preventDefault();
   var url = "/pins";
   var sep = "?";
-  ["reset", "isp", "conn", "ser", "swap"].forEach(function(p) {
+  ["reset", "isp", "conn", "ser", "swap", "txen"].forEach(function(p) {
     url += sep + p + "=" + $("#pin-"+p).value;
     sep = "&";
   });
diff --git a/serial/serbridge.c b/serial/serbridge.c
index 7ba8e8e..ff85694 100644
--- a/serial/serbridge.c
+++ b/serial/serbridge.c
@@ -18,7 +18,7 @@
 static struct espconn serbridgeConn1; // plain bridging port
 static struct espconn serbridgeConn2; // programming port
 static esp_tcp serbridgeTcp1, serbridgeTcp2;
-static int8_t mcu_reset_pin, mcu_isp_pin;
+static int8_t mcu_reset_pin, mcu_isp_pin, tx_enable_pin;
 
 uint8_t in_mcu_flashing;   // for disabling slip during MCU flashing
 
@@ -557,9 +557,10 @@ serbridgeInitPins()
 {
   mcu_reset_pin = flashConfig.reset_pin;
   mcu_isp_pin = flashConfig.isp_pin;
+  tx_enable_pin = flashConfig.tx_enable_pin;
 #ifdef SERBR_DBG
-  os_printf("Serbridge pins: reset=%d isp=%d swap=%d\n",
-      mcu_reset_pin, mcu_isp_pin, flashConfig.swap_uart);
+  os_printf("Serbridge pins: reset=%d isp=%d tx_enable=%d swap=%d\n",
+      mcu_reset_pin, mcu_isp_pin, tx_enable_pin, flashConfig.swap_uart);
 #endif
 
   if (flashConfig.swap_uart) {
@@ -578,12 +579,25 @@ serbridgeInitPins()
     system_uart_de_swap();
   }
 
-  // set both pins to 1 before turning them on so we don't cause a reset
-  if (mcu_isp_pin >= 0)   GPIO_OUTPUT_SET(mcu_isp_pin, 1);
-  if (mcu_reset_pin >= 0) GPIO_OUTPUT_SET(mcu_reset_pin, 1);
-  // switch pin mux to make these pins GPIO pins
-  if (mcu_reset_pin >= 0) makeGpio(mcu_reset_pin);
-  if (mcu_isp_pin >= 0)   makeGpio(mcu_isp_pin);
+  /* set both pins to 1 before turning them on (so we don't cause a reset)
+   * then switch pin mux to make these pins GPIO pins
+   */
+  if (mcu_isp_pin >= 0) {
+    GPIO_OUTPUT_SET(mcu_isp_pin, 1);
+    makeGpio(mcu_isp_pin);
+  }
+
+  if (mcu_reset_pin >= 0) {
+    GPIO_OUTPUT_SET(mcu_reset_pin, 1);
+    makeGpio(mcu_reset_pin);
+  }
+
+  // set TX_ENABLE to 0 so we start up listening
+  if (tx_enable_pin >= 0) {
+    GPIO_OUTPUT_SET(tx_enable_pin, 0);
+    makeGpio(tx_enable_pin);
+  }
+  //uart0_set_tx_enable_pin(tx_enable_pin); // must set to -1 if that's its value
 }
 
 // Start transparent serial bridge TCP server on specified port (typ. 23)