Shelly Pro Dimmer 1PM Connector_RCA There is a built-in USB

There is a built-in USB to UART function on board

Dimensions: 28

And just like the Feather M0 Express there is also an external 2Mbyte flash memory where you can store files systems or whatever that you need

All-in-one design with protective cover

the Red wire to 4

Shelly Pro Dimmer 1PM Connector_RCA There is a built-in USBThe Shelly Pro Dimmer 1PM is a DIN rail mountable, single channel smart dimmer with power monitoring. Use it to control, dim, and power measure a wide range of halogen lights, dimmable LED, and ferromagnetic transformers between 110 240V, with Ethernet LAN, WiFi, Bluetooth and MQTT support. Different types of actions, scenarios, and schedules can be set to sync your environment to your daily activities or business needs, via the Shelly smart home