From 5b5deb5a7784702b0c71a5bea1cfa15bac9b7256 Mon Sep 17 00:00:00 2001
From: Markus Sattler <help.markus+git@gmail.com>
Date: Sun, 17 May 2015 13:43:49 +0200
Subject: [PATCH] improve os_printf handling when buffer full.  - wait for free
 buffer in hw fifo

---
 cores/esp8266/HardwareSerial.cpp | 46 +++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/cores/esp8266/HardwareSerial.cpp b/cores/esp8266/HardwareSerial.cpp
index bdcd45716..ac56919ca 100644
--- a/cores/esp8266/HardwareSerial.cpp
+++ b/cores/esp8266/HardwareSerial.cpp
@@ -42,12 +42,12 @@ extern "C" {
 #define UART_TX_FIFO_SIZE 0x80
 
 struct uart_ {
-    int uart_nr;
+        int uart_nr;
     int baud_rate;
     bool rxEnabled;
     bool txEnabled;
-    uint8_t rxPin;
-    uint8_t txPin;
+        uint8_t rxPin;
+        uint8_t txPin;
 };
 
 static const int UART0 = 0;
@@ -120,7 +120,7 @@ void ICACHE_RAM_ATTR uart_interrupt_handler(uart_t* uart) {
     // -------------- UART 0 --------------
     if(Serial.isRxEnabled()) {
         while(U0IS & (1 << UIFF)) {
-            Serial._rx_complete_irq((char)(U0F & 0xff));
+            Serial._rx_complete_irq((char) (U0F & 0xff));
             U0IC = (1 << UIFF);
         }
     }
@@ -135,7 +135,7 @@ void ICACHE_RAM_ATTR uart_interrupt_handler(uart_t* uart) {
 
     if(Serial1.isRxEnabled()) {
         while(U1IS & (1 << UIFF)) {
-            Serial1._rx_complete_irq((char)(U1F & 0xff));
+            Serial1._rx_complete_irq((char) (U1F & 0xff));
             U1IC = (1 << UIFF);
         }
     }
@@ -357,19 +357,19 @@ void uart_swap(uart_t* uart) {
     switch(uart->uart_nr) {
         case UART0:
             if(uart->txPin == 1 && uart->rxPin == 3) {
-                pinMode(15, FUNCTION_4);//TX
-                pinMode(13, FUNCTION_4);//RX
+                pinMode(15, FUNCTION_4); //TX
+                pinMode(13, FUNCTION_4); //RX
                 USWAP |= (1 << USWAP0);
-                pinMode(1, INPUT);//TX
-                pinMode(3, INPUT);//RX
+                pinMode(1, INPUT); //TX
+                pinMode(3, INPUT); //RX
                 uart->rxPin = 13;
                 uart->txPin = 15;
             } else {
-                pinMode(1, SPECIAL);//TX
-                pinMode(3, SPECIAL);//RX
+                pinMode(1, SPECIAL); //TX
+                pinMode(3, SPECIAL); //RX
                 USWAP &= ~(1 << USWAP0);
-                pinMode(15, INPUT);//TX
-                pinMode(13, INPUT);//RX
+                pinMode(15, INPUT); //TX
+                pinMode(13, INPUT); //RX
                 uart->rxPin = 3;
                 uart->txPin = 1;
             }
@@ -400,6 +400,14 @@ void uart0_write_char(char c) {
             return;
         }
     }
+
+    // wait for the Hardware FIFO
+    while(true) {
+        if(((USS(0) >> USTXC) & 0xff) <= (UART_TX_FIFO_SIZE - 2)) {
+            break;
+        }
+    }
+
     if(c == '\n') {
         USF(0) = '\r';
     }
@@ -416,6 +424,14 @@ void uart1_write_char(char c) {
             return;
         }
     }
+
+    // wait for the Hardware FIFO
+    while(true) {
+        if(((USS(1) >> USTXC) & 0xff) <= (UART_TX_FIFO_SIZE - 2)) {
+            break;
+        }
+    }
+
     if(c == '\n') {
         USF(1) = '\r';
     }
@@ -469,11 +485,11 @@ void HardwareSerial::begin(unsigned long baud, byte config) {
     }
 
     if(_uart->rxEnabled) {
-        if (!_rx_buffer)
+        if(!_rx_buffer)
             _rx_buffer = new cbuf(SERIAL_RX_BUFFER_SIZE);
     }
     if(_uart->txEnabled) {
-        if (!_tx_buffer)
+        if(!_tx_buffer)
             _tx_buffer = new cbuf(SERIAL_TX_BUFFER_SIZE);
     }
     _written = false;