Easy USB

I’ve used FTDI chips to add USB to projects before. The last time I tried them, they were pretty easy to use (provided you can handle surface mount). Basically, your PC software saw a serial port and you would hook the chip up to your microcontroller’s serial port. However, you did need a bunch of support components to make it work.

I recently picked up the latest version of FTDI’s chip — the FT232RL. They can hardly make this any simpler. The reference schematic shows a capacitor on the 3.3V output (the chip gets its power from the USB port). It also shows a handful of capacitors and a ferrite bead that are marked “optional” (although if you need to pass FCC acceptance, you probably need them). I left off all the extra parts including the 3.3V output capacitor.

I soldered the chip on a DIP adapter. I also got a Kobiconn USB connector (Mouser 154-UAR80). This is the “wrong” kind of connector. Its the skinny kind, not the fat kind (I always get A and B mixed up). However, it has 4 pins inline on .1″ center. However, the pins are too thin for a breadboard so I put them in a strip of machine pin sockets and soldered the “back” pin to the sockets for stability.

This let me put the USB connector in a breadboard and the chip too. I had to have a USB cable with two “skinny ends” (I happened to have one). A rubber band helped hold the connector down to the board and offered some strain relief.

That’s it: the chip, the connector, and some wire. I put two 5V LEDs on the handshaking outputs so I could turn them on and off with RealTerm (a good program for messing with serial ports; find it on SourceForge). I plugged the cable into the lab PC and it came up looking for drivers. I loaded the FTDI drivers and wound up with COM29 (that machine has a large number of serial ports already — don’t ask). Sure enough, manipulating COM29 with RealTerm caused things to happen down at the breadboard.

What could be easier?

Add a USB Host to your Microcontroller

Wow, this looks interesting: . For about $30 (chip) or $60 (board) you can get a device that allows you to connect USB devices including storage, printers, and HID devices to any microcontroller that can so serial I/O, SPI, or I2C. It also has a hook up for flash cards. I haven’t tried it (yet) but if it works as advertised, its amazing!