Trying to control a Canon300D via USB-RS232 prolific converter

I am trying to control my canon digital rebel following this guide. http://www.mvkonnik.info/2008/08/long-time-remote-shooting-with-canon.html

I had it working about two weeks ago, then today I started writing my own GTK based application around this idea but when I tried to run it again. I got nothing. The camera wouldn't click or anything and I'm not even sure how to test where the problem is.

My prolific driver is installed

===dmesg===

[65150.173520] usb 3-1: new full speed USB device using uhci_hcd and address 13 [65150.340526] usb 3-1: configuration #1 chosen from 1 choice [65150.343480] usbserial_generic 3-1:1.0: generic converter detected [65150.343540] usb 3-1: generic converter now attached to ttyUSB0

===lsusb===

Bus 003 Device 013: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

===modprobe -l usbserial

kernel/drivers/usb/serial/usbserial.ko

I've tried sending all 4 different commands in different order, but I'm开发者_StackOverflow社区 not really sure about the underlying RTS and DTR signals. Does anyone know if there is a way that I can test whether my connection is working? Could I echo 1 > /dev/ttyUSB0 and connect a voltmeter to see if anything changes?

The only way I know to see if it's working is to connect the camera and try it, but it's not working and I don't know how else to troubleshoot it. Anyone have any ideas?

Simplest serial port test for your computer, USB converter, and driver setup is to get yourself a scrap of wire, paperclip, unbent staple, etc you can use to jumper pin 2 to 3 for loopback. Open a terminal on the serial port (with hardware flow control disabled).

The type random keys both with an without the jumper and verify either of the following difference:

If you have half duplex setting, with no jumper you should see no echoing and with the jumper you should see what you type.

If you have full duplex setting, with no jumper you should see each key once, and with the jumper you should see it display twice

You can also do the jumpering at the camera end of the cable if you can determine the pinout there, and include the cable in your test.

Of course the problem could be with the camera itself, or the baud rate or bit format settings could have gotten changed.