Better instructions for modifying one of the PCB types found in DKU-5 cables. These contain a prolific 2303HX which works fine for many serial purposes, speed up to 115200 settable in the standard baud rate settings (not continuously)
I’ve seen 3 different layouts for the pcb’s in the DKU-5 cables so far, this is what I call “Type A”, the one I run into most often:
Make a cable for the 6 pin header on your volksduino, boarduino, or other compatible device. There should be a cap between pin 6 of the ‘ftdi’ 6 pin header (green) and the reset pin on the arduino’s atmega chip (pin 1)
I use PATA IDE cables for the 6 pin header (connecting the vertical wires so there’s 2 of the 6 pin rows)
See the previous blog post by me for a picture of one of these cut-up IDE cables.
If you run into different PCB’s, it’s easy to figure the pinout for different pcb layouts of these common prolific 2303hx boards on your own. A rough run down of the steps to do this (my steps require a DMM and some Linux system) follows:
1) Cut out the pcb from the cable and figure out VCC and GND with continuity settings on a DMM, I use a vised hacksaw and cut the sides off.
2) Plug the board into a usb hub and see if it shows up it in your system (Linux: use dmesg and ls /dev/ttyUSB*)
3) Figure out and label possible RX and TX subjects with the voltmeter setting of your DMM.
4) Find DTR# easily by opening the Arduino software and pressing send a sketch over the connected dku-5 board. Don’t hook up a arduino, hook up your dmm to GND and the test point. DTR# to GND voltage should be ~3.3v with the device first connected to your system, get pulled to ~0V when the Arduino software starts, and then blip high every time you attempt to send a sketch out. There’s a way to toggle DTR#, CTS#, and RTS#, all the modem lines using other tools like cu, stty, minicom, and IOCTL, but I don’t remember how since I first did this.
5) build a cable and solder it on to your dku-5 pcb. Test it by opening your device in the linux terminal program screen (‘screen /dev/yourdevice 9600′), connecting pin 4 to pin 5 with a wire for loopback between TX and RX, and looking for text echo on your screen terminal when typing. Follow that up with an Arduino test by uploading a sketch.
Note: These prolific chips work at 3.3v but supply the arduino at 5v. The RX from the ‘uino back into the 2303hx is
tolerant of 5v (from the 2303hx datasheet, page 10: Schmitt inputs, 5v tolerant http://www.prolific.com.tw/eng/downloads.asp?ID=23 )