USB Sensor
Contents
This page is a stub to talk about the development of a low cost USB based sensor board
People
This board was based on discussions between:
Edward Baafi
Arjun Sarwal
David Cavallo
Cost
~$2 of parts
Input/Output
3ADC/GPIO pins
1 GPIO only pin
Features
No special USB Connector - Board IS the USB connector
No USB Hardware - Firmware based USB stack (based on low cost ATTiny45 Microcontroller)
Reprogrammable / Extensible
Current Status
Current firmware only uses one of the four I/O pins as sensor input (1 pin used for LED which indicates state, 1 pin used for button to start operation)
Sensor board shows up as a usb keyboard and dumps data as if typing from keyboard
Single layer board to make possible homemade boards using chemical etch, or mechanical milling (see pics below)
Board based on the AVR USB - EasyLogger reference design
Eagle board file is available here and schematic is available here
Firmware is available here]
TO DO
Update firmware to use 4 pins (3 ADC / 1 Digital In)
Develop/adopt scheme to implement USB CDC device and access through pyUSB (libUSB wrapper) and update firmware
Make CDC device available to Measure/Etoys/Scratch
Update board to drop hardwired button and led (could always be added by user) and reduce size of board
