From f2df542cb1c8d20102af3d752b6487f49aac038c Mon Sep 17 00:00:00 2001
From: Jan Grewe <jan@faked.org>
Date: Thu, 22 Dec 2022 08:14:11 +0100
Subject: [PATCH] Allow ignoring of failed Modbus response CRC (#3930)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
---
 esphome/components/modbus/__init__.py | 6 ++++--
 esphome/components/modbus/modbus.cpp  | 9 +++++++--
 esphome/components/modbus/modbus.h    | 2 ++
 esphome/const.py                      | 1 +
 4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/esphome/components/modbus/__init__.py b/esphome/components/modbus/__init__.py
index 254322d097..6fea7033f2 100644
--- a/esphome/components/modbus/__init__.py
+++ b/esphome/components/modbus/__init__.py
@@ -6,6 +6,7 @@ from esphome.const import (
     CONF_FLOW_CONTROL_PIN,
     CONF_ID,
     CONF_ADDRESS,
+    CONF_DISABLE_CRC,
 )
 from esphome import pins
 
@@ -27,6 +28,7 @@ CONFIG_SCHEMA = (
             cv.Optional(
                 CONF_SEND_WAIT_TIME, default="250ms"
             ): cv.positive_time_period_milliseconds,
+            cv.Optional(CONF_DISABLE_CRC, default=False): cv.boolean,
         }
     )
     .extend(cv.COMPONENT_SCHEMA)
@@ -45,8 +47,8 @@ async def to_code(config):
         pin = await gpio_pin_expression(config[CONF_FLOW_CONTROL_PIN])
         cg.add(var.set_flow_control_pin(pin))
 
-    if CONF_SEND_WAIT_TIME in config:
-        cg.add(var.set_send_wait_time(config[CONF_SEND_WAIT_TIME]))
+    cg.add(var.set_send_wait_time(config[CONF_SEND_WAIT_TIME]))
+    cg.add(var.set_disable_crc(config[CONF_DISABLE_CRC]))
 
 
 def modbus_device_schema(default_address):
diff --git a/esphome/components/modbus/modbus.cpp b/esphome/components/modbus/modbus.cpp
index 4d75675d0f..137fb0b26b 100644
--- a/esphome/components/modbus/modbus.cpp
+++ b/esphome/components/modbus/modbus.cpp
@@ -102,8 +102,12 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
     uint16_t computed_crc = crc16(raw, data_offset + data_len);
     uint16_t remote_crc = uint16_t(raw[data_offset + data_len]) | (uint16_t(raw[data_offset + data_len + 1]) << 8);
     if (computed_crc != remote_crc) {
-      ESP_LOGW(TAG, "Modbus CRC Check failed! %02X!=%02X", computed_crc, remote_crc);
-      return false;
+      if (this->disable_crc_) {
+        ESP_LOGD(TAG, "Modbus CRC Check failed, but ignored! %02X!=%02X", computed_crc, remote_crc);
+      } else {
+        ESP_LOGW(TAG, "Modbus CRC Check failed! %02X!=%02X", computed_crc, remote_crc);
+        return false;
+      }
     }
   }
   std::vector<uint8_t> data(this->rx_buffer_.begin() + data_offset, this->rx_buffer_.begin() + data_offset + data_len);
@@ -139,6 +143,7 @@ void Modbus::dump_config() {
   ESP_LOGCONFIG(TAG, "Modbus:");
   LOG_PIN("  Flow Control Pin: ", this->flow_control_pin_);
   ESP_LOGCONFIG(TAG, "  Send Wait Time: %d ms", this->send_wait_time_);
+  ESP_LOGCONFIG(TAG, "  CRC Disabled: %s", YESNO(this->disable_crc_));
 }
 float Modbus::get_setup_priority() const {
   // After UART bus
diff --git a/esphome/components/modbus/modbus.h b/esphome/components/modbus/modbus.h
index 95414ba090..dd8732c6e9 100644
--- a/esphome/components/modbus/modbus.h
+++ b/esphome/components/modbus/modbus.h
@@ -30,12 +30,14 @@ class Modbus : public uart::UARTDevice, public Component {
   void set_flow_control_pin(GPIOPin *flow_control_pin) { this->flow_control_pin_ = flow_control_pin; }
   uint8_t waiting_for_response{0};
   void set_send_wait_time(uint16_t time_in_ms) { send_wait_time_ = time_in_ms; }
+  void set_disable_crc(bool disable_crc) { disable_crc_ = disable_crc; }
 
  protected:
   GPIOPin *flow_control_pin_{nullptr};
 
   bool parse_modbus_byte_(uint8_t byte);
   uint16_t send_wait_time_{250};
+  bool disable_crc_;
   std::vector<uint8_t> rx_buffer_;
   uint32_t last_modbus_byte_{0};
   uint32_t last_send_{0};
diff --git a/esphome/const.py b/esphome/const.py
index 19fc226dd9..f0b0c089bf 100644
--- a/esphome/const.py
+++ b/esphome/const.py
@@ -175,6 +175,7 @@ CONF_DIO_PIN = "dio_pin"
 CONF_DIR_PIN = "dir_pin"
 CONF_DIRECTION = "direction"
 CONF_DIRECTION_OUTPUT = "direction_output"
+CONF_DISABLE_CRC = "disable_crc"
 CONF_DISABLED_BY_DEFAULT = "disabled_by_default"
 CONF_DISCONNECT_DELAY = "disconnect_delay"
 CONF_DISCOVERY = "discovery"