On Tue, Jun 28, 2011 at 9:19 AM, Domien Nowicki <domien.nowi...@gmail.com>wrote:
> ** > 1. The USB Blaster clone does not use the original FT245 chip, and so it > tries to emulate its behavior. > As it turns out, the API call FT_GetLatencyTimer is not properly emulated > by the clone, and this makes OpenOCD abort. In reality, this API call is not > necessary, so I have removed this call. > Are you sure this is not the bug in FTD2XX on Linux that was mentioned on this list recently? In that case, libftdi shouldn't be affected so it could be left as-is. For ft2232 the error was changed to a warning as a workaround (if that patch got merged), perhaps do the same here? 2. The LED blink code that was added in commit (24943498e611649a540d98406288dd6d4889851d) > made the JTAG communication unstable, see > http://openocd.git.sourceforge.net/git/gitweb.cgi?p=openocd/openocd;a=commitdiff;h=24943498e611649a540d98406288dd6d4889851d. > The USB Blaster dongle would properly detect the IDCODE, but would later > fail when trying to read/write the DPACC ARM JTAG registers. Not surpringly, > this is because the blink code resets the out_value, which keeps track of > the state of the JTAG pins. > In my tests, disabling or blinking the LED flag made JTAG communication > very unstable. This flag needs to be permanently enabled for proper > operation. > Do you have a clue as to WHY the LED signal must be set for the dongle to function properly? I don't know the internals of the USB Blaster in detail, but it doesn't sound right. For sure, all our USB Blasters blink when used with the Altera tools. No problem there. If out_value keeps state, the blink function is obviously broken, but I don't see why it couldn't be fixed by modifying only the LED bit in out_value. Also, why have you added commented out code? If it doesn't work (it doesn't), don't add it. Of course the better solution would be to make it work. (Hint: fix the bit clear, should be ~LED.) /Andreas
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