Many Mettler Toledo scales provide RS232 interfaces for control and measure purposes.

Metosi is single header C library covering basic features of Mettler Toledos SICS protocol.

See included hello_scale.ino example code on how to run metosi with ESP32-Arduino.

Metosi is a private project and not affiliated with Mettler Toledo. Metosi is provided as is.

I do not take responsibility for any damage that might happen as a result of using this code.

Attention: You might need to use a logic-level shifter to connect scale and µC. A minimal setup consists of a voltage divider between scales Tx and µC Rx.

1. #include "metosi.h"

2. Implement the following helper method needed by metosi to communicate, char per char, with the scale:

• void metosi_send_char(const char* msg)

3. provide the following callbacks to run when metosi receives a response including meaurement, tare, zero, serialnumber or busy information:

• void metosi_measurement_cb(uint8_t rv, float weight, char* unit)
• void metosi_tare_cb(int rv)
• void metosi_zero_cb)(int rv)
• void metosi_serialnumber_cb (uint32_t SN)
• void metosi_scale_busy_cb(void)

call metosi_read(char c) with every single char you received from your scale.

Send commands to scale with scale_cmd(char* cmd).

Implemented commands are:

SCALE_TARE_CMD
SCALE_MEASURE_CMD
SCALE_DISPLAY_CMD
SCALE_DISPLAY_WEIGHT_CMD
SCALE_ZERO_CMD
SCALE_RESET_CMD
SCALE_POWER_OFF_CMD
SCALE_POWER_ON_CMD

example of how to request a single measurement:

• call scale_cmd(SCALE_MEASURE_CMD);
• wait for scale to reply with measurement and metosi to execute metosi_measurement_cb(uint8_t rv, float weight, char* unit)

The scale might not be able to handle multiple querys one after the other. Always wait for a certain amount of milliseconds or (better) await response before sending next command.

scale_display(const char* text) print text to the scales screen.

To switch back to standard weight display call scale_cmd(SCALE_DISPLAY_WEIGHT_CMD);