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I've recently bought an Olimx ARM-USB-OCD JTAG programmer but I've had difficulty getting it to work.

My primary system is linux, but I've tested it in window with no luck there either. I'm using OpenOCD to communicate with the device, but it does not detect the ftdi chip on the programmer.

I suspect the hardware is dodgy, for two reasons. The programmer has the ability to power a board at 5V,9V or 12V, but when I measure the output voltage it is only at 0.7~1V (when connected to USB, tested on 3 different computers and one usb hub); additionally, when conncted to linux, the ftdi chip is detected, but it connects and disconnect quickly leaving a number of errors in syslog.

My questions are (and I'm most interested in anyone who has the same programmer): is the hardware broken? If not, what am I likely to be doing wrong?

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  • \$\begingroup\$ That's some weird power options...by far the most common ARM voltage I've seen is 3.3V. \$\endgroup\$
    – davr
    Commented Dec 2, 2009 at 1:18
  • \$\begingroup\$ The arm process on the board is at 3.3volts (and I'd expect the JTAG connector to adapt to this voltage too), the 5-9-12V supply is to power a board. \$\endgroup\$
    – talex
    Commented Dec 2, 2009 at 2:07

3 Answers 3

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Check how much current your board needs. From memory, the ARM-USB-OCD can only supply a few 10's of milliamps. It is not uncommon for a dev board to use a couple of hundred. As a trouble shooting step, try getting openocd to communicate with the JTAG adapter without it connected to the board.

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  • \$\begingroup\$ I've tried it with the power connected and unconnected to the target board (Olimex SAM7-P256) with no luck. \$\endgroup\$
    – talex
    Commented Dec 2, 2009 at 2:05
  • \$\begingroup\$ I can't think of anything else obvious to try. Maybe it is toast :(. \$\endgroup\$
    – Clint Lawrence
    Commented Dec 3, 2009 at 5:31
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For future reference, I've solved this problem.

Turns out the two USB cables I'd been trying to use have a high impedance (~6 ohms), when I used a cable with an impedance closer to 1 ohm it worked fine...

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... can be used as power supply to your target board with three jumper selectable power supplies: 5V 9V and 12VDC, USB source current is limited with resetable fuse at 300mA, at the different output voltage the maximum current is different: 5V/200mA, 9V/100mA, 12V/70mA, note that this also depend on your USB host current capabilities, if other USB devices are attached to your computer or if the laptop is running on batteries these figures may be different and depend on your computer USB host.

(from http://www.olimex.com/dev/arm-usb-ocd.html)

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