Nuts and Volts - July 2014

when the download cable is disconnected, which could result in noise pickup that might interfere with program execution. Their importance is clearly explained in PICAXE documentation.

If you want your download cable to be really small, take a look at Jim Paris' FTXUSB serial breakout board ( www.tindie.com/products/jimparis/microftx-usb-serial- breakout-1/?pt=directsearch). At only 0.4" x 0.64" — including a micro USB B connector — it's the smallest cable currently being made. It uses a tiny FT230XQ chip with RX and TX signals that you can invert with FTProg.

The cost is a little over $12 shipped, to which you must add a USB micro cable and an output cable. The next largest category is the CRIUS FTDI basic breakout board from DealExtreme ( www.deal extreme.com). At only $6.59 (including shipping), this high quality FTDI board also doesn't need extra inverters. All you would need to do would be to install input and output cables and use FTProg to invert RX and TX.

Omega MCU Systems sells a board with an SI Labs CP2103 chip and a couple of transistor inverters added

( www.onebytecpu.com/usermanuals/u2p_datasheet.pdf), but it costs about $15 shipped, and you would still need cables. It's also a little clunky.

You can buy a postage stamp-sized MCP2200 breakout board direct from the manufacturer (Microchip) or from major electronics suppliers (Digi-Key, Mouser, Newark, Farnell, etc.) for $15 plus shipping. Microchip provides an EEPROM configuration utility that is similar to FTProg that allows you to invert the RX and TX signals. All you would need to add would be cables.

For the lowest cost download cable, you can use a USB-to-TTL converter module based on a Prolific PL- 2303HX chip or an SI Labs CP-2102 or 2103 chip. These are available from many sources in China, Taiwan, and Hong Kong. Figure 3 shows some examples.