Jul 112009

While browsing the web page of my favourite electronics shop in Akihabara Akizukidenshi (秋月電子) I saw this small USB module. Originally to connect things like FPGAs, microcontroller etc. which cannot use serial ports, it also has a bit-bang mode where it simply outputs on 8 data ports whatever you like. There’s a simple to use library available libftdi which can make those chip and its port directly accessible in Linux (and more).

The data sheet for that chip is at best spotty, but the chip works as advertised.

Some highlights of the FTDI 245RL and the above module in particular:

  • 8 data ports
  • I/O can be 3.3V or 5V
  • each I/O pin can be set to input or output independantly
  • Has a 3.3V step-down converter already built in
  • Can output 1MByte/second
  • Has an unique ID burnt into the chip
  • Can source and sink 2mA normally, or 3 resp. 8mA when in high-drive mode
  • 1 kb EEPROM is built in too

Quite versatile. Combine with a small Linux host (like this which I happen to have) and for many applications which need network and some I/O, this is an easier way to get things done compared with a stand-along microcontroller. As long as weight/power consumption and lack of low-latency (millisecond range or faster) is no issue, it’s at least easier to get started and you can use all the amenities of Linux (free choice of programming language, Internet connectivity, a clock, daemons for cron and at etc).