Magic Mote

This compact PCB interfaces a low power MSP430G2553 microcontroller with a Nordic NRF24L01+ 2.4 GHz radio frequency transceiver module. It's well adapted to serve as a wireless sensor node but has enough I/O options to be put to use wherever a small microcontroller is required.

Version 2 of this versatile board features a more accessible tactile switch and an IDC compatible programming/serial header.

Use Cases

We think these are ideal for home automation. For example, 2 Magic Motes were used in the radio thermostat recently featured on Hack A Day. One Mote acted as a wireless thermometer, continuously sending radio signals to a second Mote in the basement that switched the heating on and off via a relay.

Magic Motes can be used in a home security system, interfacing with PIR sensors to detect motion/intrusion, reed switches that signal when windows or doors are opened, or gas detectors that sense smoke or carbon monoxide.

How about hands-free, auto-off hallway lights... or an automatic mailbox? All these applications, and more, can be linked with a network of sensors reporting to a master node.

Details

Each order is for one pair of bare PCBs (2) with green solder mask and HASL finish. The boards are a shade under 1" x 2" (24.5 x 49 mm) with radiused corners and 1/8" (3.2 mm) diameter standoffs.

A pair of Magic Motes can be hand soldered to your specifications. The motes include RF modules and your choice of battery holder. There may be a lead time to order parts. Contact Magic Smoke for details.

Technical Specifications

Nordic NRF24L01+ RF modules are extremely cheap (~$1), use very little power, and have sufficient range for most indoor projects.

Low power MSP430 microcontrollers make an ideal partner for battery powered applications. The MSP430G2553 is a capable 16-bit chip with 8 kB flash, 0.5 kB RAM, and plenty of peripherals. The cheaper MSP430G2452 can be substituted if hardware UART is not required.

Either chip can be programmed using the Arduino-compatible Energia environment, or C/C++/assembler using a number of freely-distributed and open source toolchains. The Enrf24 (Energia) and msprf24 (pure C) libraries are recommended to interface the NRF24L01+ module.

Power can be supplied to the board from a 20 mm Lithium coin cell or 2xAA battery pack. I/O options include a 3.5 mm jack socket or 3-pin header, a 4-pin header with an analogue input, and a 6-pin programming/serial header.

Resources

• Github repository with PCB design files and documentation.
• Github repository with code and documentation for the home thermostat project.
• Enrf24 and msprf24 libraries to interface the NRF24L01+ modules.