From 2f78308de0efdbedf1414177e2d0fceb6b9287eb Mon Sep 17 00:00:00 2001
From: Igor Mammedov <imammedo@redhat.com>
Date: Thu, 23 May 2019 18:45:06 +0200
Subject: [PATCH] uart: add drain() API

it would allow to empty RX buffer when necessary

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 esphome/components/uart/uart.cpp | 29 +++++++++++++++++++++++++++++
 esphome/components/uart/uart.h   |  5 +++++
 2 files changed, 34 insertions(+)

diff --git a/esphome/components/uart/uart.cpp b/esphome/components/uart/uart.cpp
index 56661b8aa7..ca74885393 100644
--- a/esphome/components/uart/uart.cpp
+++ b/esphome/components/uart/uart.cpp
@@ -98,6 +98,14 @@ void UARTComponent::flush() {
   ESP_LOGVV(TAG, "    Flushing...");
   this->hw_serial_->flush();
 }
+
+void UARTComponent::drain() {
+  for (int i = 0; this->available(); i++) {
+    uint8_t junk;
+    this->read_byte(&junk);
+    ESP_LOGVV(TAG, "Draining RX[%d]: %0x", i, junk);
+  }
+}
 #endif  // ESP32
 
 #ifdef ARDUINO_ARCH_ESP8266
@@ -235,6 +243,19 @@ void UARTComponent::flush() {
   }
 }
 
+void UARTComponent::drain() {
+  if (this->hw_serial_ != nullptr) {
+    for (int i = 0; this->available(); i++) {
+      uint8_t junk;
+      this->read_byte(&junk);
+      ESP_LOGVV(TAG, "Draining RX[%d]: %0x", i, junk);
+    }
+  } else {
+    this->sw_serial_->drain();
+  }
+}
+
+
 void ESP8266SoftwareSerial::setup(int8_t tx_pin, int8_t rx_pin, uint32_t baud_rate) {
   this->bit_time_ = F_CPU / baud_rate;
   if (tx_pin != -1) {
@@ -321,6 +342,14 @@ uint8_t ESP8266SoftwareSerial::peek_byte() {
   return this->rx_buffer_[this->rx_out_pos_];
 }
 void ESP8266SoftwareSerial::flush() { this->rx_in_pos_ = this->rx_out_pos_ = 0; }
+
+void ESP8266SoftwareSerial::drain() {
+  for (int i = 0; this->available(); i++) {
+    uint8_t junk = this->read_byte();
+    ESP_LOGVV(TAG, "Draining RX[%d]: %0x", i, junk);
+  }
+}
+
 int ESP8266SoftwareSerial::available() {
   int avail = int(this->rx_in_pos_) - int(this->rx_out_pos_);
   if (avail < 0)
diff --git a/esphome/components/uart/uart.h b/esphome/components/uart/uart.h
index 005536de4a..28cf7f69d0 100644
--- a/esphome/components/uart/uart.h
+++ b/esphome/components/uart/uart.h
@@ -16,6 +16,7 @@ class ESP8266SoftwareSerial {
   uint8_t peek_byte();
 
   void flush();
+  void drain();
 
   void write_byte(uint8_t data);
 
@@ -62,6 +63,8 @@ class UARTComponent : public Component, public Stream {
 
   void flush() override;
 
+  void drain();
+
   float get_setup_priority() const override { return setup_priority::BUS; }
 
   size_t write(uint8_t data) override;
@@ -109,6 +112,8 @@ class UARTDevice : public Stream {
 
   void flush() override { return this->parent_->flush(); }
 
+  void drain() { return this->parent_->drain(); }
+
   size_t write(uint8_t data) override { return this->parent_->write(data); }
   int read() override { return this->parent_->read(); }
   int peek() override { return this->parent_->peek(); }