Summary

• AVR ATtiny841 MCU (8Ki flash, 512B RAM, 128B EEPROM)
• CC1101 radio (868MHz band)
• USART, I²C, 2xGPIO header
• 3V to 3.6V operation - ideal for LiFePO4
• Fully assembled

What is it?

An ATtiny814 microcontroller on a small breakout board which integrates a CC1101 radio module, tuned to the 868MHz band. The radio module is connected to the SPI pins of the microcontroller and is supplied fully assembled, so all you need to do is upload firmware to the chip via the UPDI breakout header and you're ready to go.

The USART and I²C peripherals from the MCU are brought out on the main header, as are two further GPIO pins, on which interrupts and PWM output are available. These options allow a wide variety of applications, such as remote control, sensing, and telemetry.

The remaining IO pins are attached to the radio module:

The board needs power around 3V to 3.6V, and is designed for being powered by a single LiFePO4 cell.

Why did you make it?

Lately I've been working on some radio-controlled tech for theatre use, and found that the usual 2.4GHz band that many radio systems run in is very crowded, with wifi and bluetooth signals all competing for bandwidth. I need local control of some LED outputs, so a microcontroller with PWM and enough spare cycles to drive a WS2812 LED chain is required.

What makes it special?

There are a variety of MCU + radio module combinations around, but most of those seem to be based on nRF24 or ESP8266 modules and run in the 2.4GHz band. This one targets the 868MHz telemetry band, where spectrum may be quieter and range longer. Combining a microcontroller with a radio running in the 868MHz band makes a convenient way to use a different part of the radio spectrum away from that crowding, with local processing to handle PWM LED outputs or driving other mechanisms by reliable remote control.