I just finished slapping together a setup in ESPHome for my Kamstrup electricity meter which uses MBus to communicate. I found there were not very many examples of using the UART integration in ESPHome, so although probably not a lot of people will have the same setup as me, maybe it can serve as an example for similar projects. Keep in mind the code is not exactly what you’d call elegant… 
ESPHome config:
esphome:
name: ams
platform: ESP32
board: nodemcu-32s
includes:
mbus.h
wifi:
power_save_mode: light
networks:
- ssid: "LulzNettOppe"
password: ##PASSWORD##
- ssid: "LulzNettEkstra"
password: ##PASSWORD##
- ssid: "LulzNett"
password: ##PASSWORD##
# Enable logging
logger:
level: DEBUG
# Enable Home Assistant API
api:
ota:
uart:
id: uart_bus
tx_pin: GPIO17
rx_pin: GPIO16
baud_rate: 2400
# Example configuration entry
dallas:
- pin: GPIO25
sensor:
- platform: dallas
address: 0xEA0214808622FF28
name: "Temperature Sikringsskap"
- platform: custom
lambda: |-
auto mbus_reader = new MbusReader(id(uart_bus));
App.register_component(mbus_reader);
return {mbus_reader->wattage_sensor, mbus_reader->reactive_power_sensor, mbus_reader->amperage_sensor, mbus_reader->voltage_sensor, mbus_reader->energy_sensor, mbus_reader->reactive_energy_sensor};
sensors:
- name: "AMS Wattage"
unit_of_measurement: kW
accuracy_decimals: 3
filters:
- multiply: 0.001
- name: "AMS Reactive Power"
unit_of_measurement: VAr
accuracy_decimals: 0
internal: true
- name: "AMS Amperage"
unit_of_measurement: A
accuracy_decimals: 2
filters:
- multiply: 0.01
- name: "AMS Voltage"
unit_of_measurement: V
accuracy_decimals: 0
- name: "AMS Hourly Energy"
unit_of_measurement: kWh
accuracy_decimals: 3
filters:
- multiply: 0.01
- name: "AMS Hourly Reactive Energy"
unit_of_measurement: kVArh
accuracy_decimals: 3
internal: true
filters:
- multiply: 0.01
mbus.h:
#include "esphome.h"
class MbusReader : public Component, public uart::UARTDevice, public Sensor {
public:
MbusReader(uart::UARTComponent *parent) : uart::UARTDevice(parent) {}
uint8_t temp_byte = 0;
uint8_t *temp_byte_pointer = &temp_byte;
uint8_t uart_buffer_[512]{0};
uint16_t uart_counter = 0;
char uart_message[550];
char temp_string[10];
char obis_code[32];
char temp_obis[10];
uint32_t obis_value = 0;
float wattage = 0;
float amperage = 0;
float voltage = 0;
float energy = 0;
Sensor *wattage_sensor = new Sensor();
Sensor *amperage_sensor = new Sensor();
Sensor *voltage_sensor = new Sensor();
Sensor *energy_sensor = new Sensor();
Sensor *reactive_power_sensor = new Sensor();
Sensor *reactive_energy_sensor = new Sensor();
void setup() override {
}
void loop() override {
bool have_message = read_message();
}
bool read_message() {
while(available() >= 1) {
read_byte(this->temp_byte_pointer);
if(temp_byte == 126) {
if(uart_counter > 2) {
uart_buffer_[uart_counter] = temp_byte;
uart_counter++;
uart_message[0] = '\0';
strcpy(uart_message, "");
for (uint16_t i = 0; i < uart_counter && i < 256; i++) {
//sprintf(temp_string, "%02X", uart_buffer_[i]);
//strncat(uart_message, temp_string, 2);
if(uart_buffer_[i-1] == 9 && uart_buffer_[i] == 6) {
obis_code[0] = '\0';
strcpy(obis_code, "");
for (uint16_t y = 1; y < 6; y++) {
sprintf(temp_obis, "%d.", uart_buffer_[i + y]);
strcat(obis_code, temp_obis);
}
sprintf(temp_obis, "%d", uart_buffer_[i + 6]);
strcat(obis_code, temp_obis);
ESP_LOGV("uart", "OBIS code found: %s message length: %d", obis_code, uart_buffer_[i + 7]);
obis_value = 0;
if(uart_buffer_[i + 7] == 6) {
for(uint8_t y = 0; y < 4; y++) {
obis_value += (long)uart_buffer_[i + 8 + y] << ((3-y) * 8);
}
} else if(uart_buffer_[i + 7] == 18) {
for(uint8_t y = 0; y < 2; y++) {
obis_value += (long)uart_buffer_[i + 8 + y] << ((1-y) * 8);
}
}
if(strcmp(obis_code, "1.1.1.7.0.255") == 0) {
ESP_LOGV("uart", "Wattage: %d", obis_value);
wattage_sensor->publish_state(obis_value);
} else if (strcmp(obis_code, "1.1.31.7.0.255") == 0) {
ESP_LOGV("uart", "Amperage: %d", obis_value);
amperage_sensor->publish_state(obis_value);
} else if (strcmp(obis_code, "1.1.32.7.0.255") == 0) {
ESP_LOGV("uart", "Voltage: %d", obis_value);
voltage_sensor->publish_state(obis_value);
} else if (strcmp(obis_code, "1.1.1.8.0.255") == 0) {
ESP_LOGV("uart", "Energy Usage Last Hour: %d", obis_value);
energy_sensor->publish_state(obis_value);
} else if (strcmp(obis_code, "1.1.4.7.0.255") == 0) {
ESP_LOGV("uart", "Reactive Power: %d", obis_value);
reactive_power_sensor->publish_state(obis_value);
} else if (strcmp(obis_code, "1.1.4.8.0.255") == 0) {
ESP_LOGV("uart", "Reactive Power Last Hour: %d", obis_value);
reactive_energy_sensor->publish_state(obis_value);
} else {
ESP_LOGV("uart", "Unknown OBIS %s, value: %d", obis_code, obis_value);
}
}
//strncat(uart_message, " ", 1);
}
ESP_LOGV("uart", "%d length received", uart_counter);
//ESP_LOGI("uart", "%d length received: %s", uart_counter, uart_message);
ESP_LOGV("uart", "Message length: %d", uart_message[3]);
uart_counter = 0;
uart_message[0] = '\0';
strcpy(uart_message, "");
} else {
uart_counter = 0;
}
}
uart_buffer_[uart_counter] = temp_byte;
uart_counter++;
}
return false;
}
};
