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[modbus] Modbus server role: write holding registers (#9156)

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This commit is contained in:
Javier Peletier
2025-07-01 15:39:06 +12:00
committed by GitHub
parent 16ef5a9377
commit 35de36d690
6 changed files with 154 additions and 16 deletions
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esphome/components/modbus/modbus.cpp
+33 -15
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@@ -90,15 +90,24 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
} else {
// data starts at 2 and length is 4 for read registers commands
if (this->role == ModbusRole::SERVER && (function_code == 0x1 || function_code == 0x3 || function_code == 0x4)) {
data_offset = 2;
data_len = 4;
}
// the response for write command mirrors the requests and data starts at offset 2 instead of 3 for read commands
if (function_code == 0x5 || function_code == 0x06 || function_code == 0xF || function_code == 0x10) {
data_offset = 2;
data_len = 4;
if (this->role == ModbusRole::SERVER) {
if (function_code == 0x1 || function_code == 0x3 || function_code == 0x4 || function_code == 0x6) {
data_offset = 2;
data_len = 4;
} else if (function_code == 0x10) {
if (at < 6) {
return true;
}
data_offset = 2;
// starting address (2 bytes) + quantity of registers (2 bytes) + byte count itself (1 byte) + actual byte count
data_len = 2 + 2 + 1 + raw[6];
}
} else {
// the response for write command mirrors the requests and data starts at offset 2 instead of 3 for read commands
if (function_code == 0x5 || function_code == 0x06 || function_code == 0xF || function_code == 0x10) {
data_offset = 2;
data_len = 4;
}
}
// Error ( msb indicates error )
@@ -132,6 +141,7 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
bool found = false;
for (auto *device : this->devices_) {
if (device->address_ == address) {
found = true;
// Is it an error response?
if ((function_code & 0x80) == 0x80) {
ESP_LOGD(TAG, "Modbus error function code: 0x%X exception: %d", function_code, raw[2]);
@@ -141,13 +151,21 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
// Ignore modbus exception not related to a pending command
ESP_LOGD(TAG, "Ignoring Modbus error - not expecting a response");
}
} else if (this->role == ModbusRole::SERVER && (function_code == 0x3 || function_code == 0x4)) {
device->on_modbus_read_registers(function_code, uint16_t(data[1]) | (uint16_t(data[0]) << 8),
uint16_t(data[3]) | (uint16_t(data[2]) << 8));
} else {
device->on_modbus_data(data);
continue;
}
found = true;
if (this->role == ModbusRole::SERVER) {
if (function_code == 0x3 || function_code == 0x4) {
device->on_modbus_read_registers(function_code, uint16_t(data[1]) | (uint16_t(data[0]) << 8),
uint16_t(data[3]) | (uint16_t(data[2]) << 8));
continue;
}
if (function_code == 0x6 || function_code == 0x10) {
device->on_modbus_write_registers(function_code, data);
continue;
}
}
// fallthrough for other function codes
device->on_modbus_data(data);
}
}
waiting_for_response = 0;