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Topic: Building the Bus Blaster v1 (Read 8133 times) previous topic - next topic

Re: Building the Bus Blaster v1

Reply #15
The 22pFs should be ok, and you don't need to the EEPROM to get it to enumerate.

If you have a magnifier or good eyes - try using a needle to move the pins ont he USB jack. The footprint is quite tight (we're using a new one int he future for easier soldering), it keeps giving me problems on lots of PCBs. You can use the needle to test the FT2232H pins too.
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Re: Building the Bus Blaster v1

Reply #16
i used to have all these problems before i had access to a stereoscope, good quality magnification can save a lot of time. not its safer than soldering with a jewelers loupe!

Re: Building the Bus Blaster v1

Reply #17
It's alive!

So, some more time with the magnifying glasses, and checking around the ft2232 with the needle probes (check the pins *and* the lands) showed that 1.8V was not getting to all of the pins.  Re-soldered all the pins just to be sure, checked for shorts, and volts (all there now!).

Plugged it and an it enumerated! FTDI drivers loaded on win7, and it looks good (COM4 & 5 now present).

(I did solder in the eeprom just for fun, know it's not needed).

My Target Present LED fades in and out on occasion with nothing plugged in (I think I just guessed at the SOT23 transistor for that circuit).

Next I need to get the ic7 buffer soldered in ...

-Crawford

Re: Building the Bus Blaster v1

Reply #18
Thanks for the update, I'm glad it's working for you.

For the LED transistor, I used a BC818xx (BC81816 or BC81840), but as long as the pinout is the same it shouldn't matter too much.
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Re: Building the Bus Blaster v1

Reply #19
For the Target Present transistor I used a SOT23 version of the 2N3904, which is pretty generic.

I may give it a shot with OpenOCD or some other JTAG tool today.

Cheers,
Crawford

Building the Bus Blaster v1 (prototype) - Mystery solved!

Reply #20
So, I was beginning to despair of this prototype version of Bus Blaster ever fully working.  None of the several JTAG-compatible devices would be detected in any tool I tried, not even my OpenBench Logic Sniffer.

But, I started buzzing out the JTAG connections and buffers, and guess what?  The TDI pin and the TMS pin are reversed, that is, connected to the wrong pins of the FT2232 !  Grr!  Arrgh!  (Note that I am not bitching about a board I got for free on PCB Sunday, just the time it took me to find this).

After a simple swap of the TDI/TMS wires, the OpenBench, the AT91SAM7S board, the Coolrunner x-board, they all detect now.

So, this perhaps begs the question: Is there a simple wire-back test (not unlike wiring Tx to Rx in rs-232) to test out the connectivity of the board?  There are 2 ports on it... (I know this is probably overcome by events with the CPLD version).

-Crawford

Re: Building the Bus Blaster v1

Reply #21
I'm really sorry about that, I was aware of this issue and thought it was listed in the Free PCB Sunday post. My epiphany on this issue arrived here, after a week of on-and-off debugging:
http://dangerousprototypes.com/forum/in ... 8#msg13688

Quote
Is there a simple wire-back test (not unlike wiring Tx to Rx in rs-232) to test out the connectivity of the board?  There are 2 ports on it... (I know this is probably overcome by events with the CPLD version).

As far as I know there is no simple loop-back test for JTAG. In the factory we have been testing against actual JTAG targets. The secondary port on v1 is unused and unexposed.

On v2 we can load a special CPLD logic that tests connectivity, but that is still a bit in the future too.
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