Remote wireless devices using the RFM12B module used in several of my projects often need an interface from where the user can interact with them. A device that could be plugged into my Apple Mac via USB seemed the most appropriate solution since I spend a good portion of my life glued to my Macs (!). So the device at its simplest would require the following components :
- USB connection to an Apple Mac
- RFM12B wireless communication
Although you can buy AVR microcontrollers that already incorporate USB connectivity as part of their hardware, they tend to be expensive and don’t generally come in an amateur-friendly DIP package, but as an infinitely-small SMD. Thankfully, the people at Objective Development have developed V-USB – ‘a software-only’ implementation of a low-speed USB device for Atmel AVR microprocessors’. And to make things really easy, they even tell you what circuitry to build for the USB connection.
This uses the standard transmitter-receiver system that is used in all devices that need to do RFM12B wireless communication of which I have elaborated upon elsewhere. In the case of this user device, which needs to connect to the computer via USB, the firmware integrates the wireless code within the necessary V-USB code.
to be continued…