# 02_telemetry
Field firmware: MQTT connect, subscribe to commands, publish telemetry.
## Code
```c
iotmer_config_t cfg = IOTMER_CONFIG_DEFAULT();
iotmer_client_t client;
iotmer_init(&client, &cfg);
iotmer_connect(&client);
iotmer_subscribe_commands(&client, on_command, NULL);
iotmer_telemetry_publish(&client, "{\"temp\":22.5,\"hum\":60}");
```
See `main/main.c` for the full connect/wait loop.
## Configure
After first provision via `01_provisioning`, leave `IOTMER_PROVISION_AUTH_CODE` empty. HTTPS is skipped when NVS holds a complete session.
## Build
```bash
idf.py set-target esp32
idf.py build flash monitor
```
To create a project from this example, run:
idf.py create-project-from-example "iotmertech/iotmer=0.2.1:02_telemetry"