From 2cf76ba784daa9eefa6a939944c0d66ec92ab2ef Mon Sep 17 00:00:00 2001
From: "Dirk O. Kaar" <dok@dok-net.net>
Date: Sun, 28 Mar 2021 21:57:46 +0200
Subject: [PATCH] HW Serial swap and pin setting work only on a few pins,
 return false on failure.

---
 cores/esp8266/HardwareSerial.h | 16 ++++-----
 cores/esp8266/uart.cpp         | 60 ++++++++++++++++++++++++----------
 cores/esp8266/uart.h           |  6 ++--
 3 files changed, 54 insertions(+), 28 deletions(-)

diff --git a/cores/esp8266/HardwareSerial.h b/cores/esp8266/HardwareSerial.h
index b8747f09d..8c27d2777 100644
--- a/cores/esp8266/HardwareSerial.h
+++ b/cores/esp8266/HardwareSerial.h
@@ -101,31 +101,31 @@ public:
         return uart_get_rx_buffer_size(_uart);
     }
 
-    void swap()
+    bool swap()
     {
-        swap(1);
+        return swap(1);
     }
-    void swap(uint8_t tx_pin)    //toggle between use of GPIO13/GPIO15 or GPIO3/GPIO(1/2) as RX and TX
+    bool swap(uint8_t tx_pin)    //toggle between use of GPIO13/GPIO15 or GPIO3/GPIO(1/2) as RX and TX
     {
-        uart_swap(_uart, tx_pin);
+        return uart_swap(_uart, tx_pin);
     }
 
     /*
      * Toggle between use of GPIO1 and GPIO2 as TX on UART 0.
      * Note: UART 1 can't be used if GPIO2 is used with UART 0!
      */
-    void set_tx(uint8_t tx_pin)
+    bool set_tx(uint8_t tx_pin)
     {
-        uart_set_tx(_uart, tx_pin);
+        return uart_set_tx(_uart, tx_pin);
     }
 
     /*
      * UART 0 possible options are (1, 3), (2, 3) or (15, 13)
      * UART 1 allows only TX on 2 if UART 0 is not (2, 3)
      */
-    void pins(uint8_t tx, uint8_t rx)
+    bool pins(uint8_t tx, uint8_t rx)
     {
-        uart_set_pins(_uart, tx, rx);
+        return uart_set_pins(_uart, tx, rx);
     }
 
     int available(void) override;
diff --git a/cores/esp8266/uart.cpp b/cores/esp8266/uart.cpp
index 3359ae6fd..7ad926cb9 100644
--- a/cores/esp8266/uart.cpp
+++ b/cores/esp8266/uart.cpp
@@ -760,11 +760,11 @@ uart_uninit(uart_t* uart)
     free(uart);
 }
 
-void
+bool
 uart_swap(uart_t* uart, int tx_pin)
 {
     if(uart == NULL)
-        return;
+        return false;
 
     switch(uart->uart_nr)
     {
@@ -788,6 +788,7 @@ uart_swap(uart_t* uart, int tx_pin)
                 pinMode(uart->rx_pin, FUNCTION_4);    //RX
 
             IOSWAP |= (1 << IOSWAPU0);
+            return true;
         }
         else
         {
@@ -808,6 +809,7 @@ uart_swap(uart_t* uart, int tx_pin)
                 pinMode(3, SPECIAL);    //RX
 
             IOSWAP &= ~(1 << IOSWAPU0);
+            return true;
         }
         break;
     case UART1:
@@ -816,13 +818,14 @@ uart_swap(uart_t* uart, int tx_pin)
     default:
         break;
     }
+    return false;
 }
 
-void
+bool
 uart_set_tx(uart_t* uart, int tx_pin)
 {
     if(uart == NULL)
-        return;
+        return false;
 
     switch(uart->uart_nr)
     {
@@ -834,12 +837,14 @@ uart_set_tx(uart_t* uart, int tx_pin)
                 pinMode(uart->tx_pin, INPUT);
                 uart->tx_pin = 2;
                 pinMode(uart->tx_pin, FUNCTION_4);
+                return true;
             }
             else if (uart->tx_pin == 2 && tx_pin != 2)
             {
                 pinMode(uart->tx_pin, INPUT);
                 uart->tx_pin = 1;
                 pinMode(uart->tx_pin, SPECIAL);
+                return true;
             }
         }
 
@@ -850,33 +855,54 @@ uart_set_tx(uart_t* uart, int tx_pin)
     default:
         break;
     }
+    return false;
 }
 
-void
+bool
 uart_set_pins(uart_t* uart, int tx, int rx)
 {
     if(uart == NULL)
-        return;
+        return false;
 
-    if(uart->uart_nr == UART0) // Only UART0 allows pin changes
+    if(uart->uart_nr != UART0) // Only UART0 allows pin changes
+        return false;
+
+    if(uart->tx_enabled && uart->tx_pin != tx)
     {
-        if(uart->tx_enabled && uart->tx_pin != tx)
+        if( rx == 13 && tx == 15)
         {
-            if( rx == 13 && tx == 15)
+            if (!uart_swap(uart, 15))
+                return false;
+        }
+        else if (rx == 3 && (tx == 1 || tx == 2))
+        {
+            if (uart->rx_pin != rx)
             {
-                uart_swap(uart, 15);
+                if (!uart_swap(uart, tx))
+                    return false;
             }
-            else if (rx == 3 && (tx == 1 || tx == 2))
+            else
             {
-                if (uart->rx_pin != rx)
-                    uart_swap(uart, tx);
-                else
-                    uart_set_tx(uart, tx);
+                if (!uart_set_tx(uart, tx))
+                    return false;
             }
         }
-        if(uart->rx_enabled && uart->rx_pin != rx && rx == 13 && tx == 15)
-            uart_swap(uart, 15);
+        else
+            return false;
     }
+
+    if (uart->rx_enabled && uart->rx_pin != rx)
+    {
+        if (rx == 13 && tx == 15)
+        {
+            if (!uart_swap(uart, 15))
+                return false;
+        }
+        else
+            return false;
+    }
+
+    return true;
 }
 
 
diff --git a/cores/esp8266/uart.h b/cores/esp8266/uart.h
index d792de665..8e08da021 100644
--- a/cores/esp8266/uart.h
+++ b/cores/esp8266/uart.h
@@ -116,9 +116,9 @@ typedef struct uart_ uart_t;
 uart_t* uart_init(int uart_nr, int baudrate, int config, int mode, int tx_pin, size_t rx_size, bool invert);
 void uart_uninit(uart_t* uart);
 
-void uart_swap(uart_t* uart, int tx_pin);
-void uart_set_tx(uart_t* uart, int tx_pin);
-void uart_set_pins(uart_t* uart, int tx, int rx);
+bool uart_swap(uart_t* uart, int tx_pin);
+bool uart_set_tx(uart_t* uart, int tx_pin);
+bool uart_set_pins(uart_t* uart, int tx, int rx);
 bool uart_tx_enabled(uart_t* uart);
 bool uart_rx_enabled(uart_t* uart);