I am looking forward to getting a Teensy++ 2.0 microcontroller board. Teensy is a low-cost, small microcontroller based on Atmel AVR technology that uses USB for the programming interface. USB can also be used by the device running the user’s programs in a variety of modes.
Teensy is something that I expect to solve a number of problems in deploying Raspberry Pi in embedded systems and instruments. The Raspberry Pi hardware exposes a number of GPIO pins, but that number is not large, and gets smaller as one uses special-purpose features like SPI and I2C, which are mapped to specific pins in the GPIO range. Raspberry Pi also has no built-in analog-to-digital capability. To protect the GPIO circuitry on the Raspberry Pi, one also has to do level-shifting to 3.3V. Attaching Teensy to a Raspberry Pi via USB does not risk the circuitry since nothing is going through the RasPi’s GPIO pins. I am intrigued by the USB HID mode, which looks like it may be amenable to a particularly flexible way of supporting two-way communication of commands and data between the two systems. Teensy also has several channels of analog-to-digital conversion built-in, as well as digital IO and PWM. With everything on and running at a full 16MHz, Teensy++ should draw less than 70 mA of 5V DC power. There is the potential for hooking up multiple Teensy systems to one RasPi via USB when using hubs.
I’ve also got multiple RasPis here, so I am in position to deploy a system and still be able to work on further development. The problem, as usual, is where to get the time.