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Trying to rescue 32 TQFP mounted on PCB

Posted: Fri Sep 26, 2014 9:10 am
by englund
Hi, I bought the rescue shield to rescue a couple of MiniWireless-HW (http://www.anarduino.com/miniwireless/) but I'm not having much success :(

I have tried both the original arduino sketch and the alternate firmware by Dennis but both fail (differently).
With the original firmware I select atmega and then connect the shield to my PCB. But then I am supposed to enter the fuses I want but when I press send to set the first (low) fuse value nothing happens in the serial terminal. I also tried to disable the interactive mode and then pressing the GO!-button. The burn LED blinks and the ready LED comes on again but the circuit on the PCB is still inaccessible to my AVR-ISP-MK2 from AVR Studio so the fuses are still broken.
The alternate firmware prompts me for the device and when I select to burn fuses it spurts out some random chars and selects something else like erase flash or read flash.

The (simple) schematic for the MiniWireless is available here: http://www.anarduino.com/miniwireless/miniWireless-sch.jpg

Please advise..

Thanks,
englund

Re: Trying to rescue 32 TQFP mounted on PCB

Posted: Fri Sep 26, 2014 9:20 pm
by mightyohm
You'll need to remove or isolate the AVR from the PCB. The HV programmer will not work if the chip is still connected to power supply, crystal, etc on the PCB.

Re: Trying to rescue 32 TQFP mounted on PCB

Posted: Sat Sep 27, 2014 4:27 am
by englund
Hmm, I would really want to avoid removing the atmega from the PCB.. Do you think I could get away by removing a few of the other components? Which ones are most likely the cause of the interference you think? For example the crystal, wouldn't that be overrided by a full swing 5V TTL?

Re: Trying to rescue 32 TQFP mounted on PCB

Posted: Sat Sep 27, 2014 10:20 am
by mightyohm
The rescue shield is not designed to work in this way. It's possible that if you remove enough components it may work. I have not tested this. At a minimum you'll need to fully disconnect the VCC and RESET lines from the associated circuitry on the board. Some traces may be under the AVR, so use a continuity tester to make sure all connections are fully broken. Ideally, for any pin that connects to the rescue shield, the rescue shield is the only device connected to that pin (and nothing on the PCB).

Re: Trying to rescue 32 TQFP mounted on PCB

Posted: Sun Sep 28, 2014 4:06 am
by englund
Thanks for the reply.. I tried removing some components using hot air but the board became a mess so I decided it was better to just toss the boards with bad fuses and buy new ones. After all the MiniWireless is "only" $15, you get alot for your money.. although a slightly larger pcb with a dip atmega in a socket would be very nice so you hace a chance to recover from bad fuses. For me the bad fuses just appeared during regular flashing when it's not supposed to touch the fuses. Guessing a bad programmer so I will use my new avr-isp-mk2 from now on when I want to mess with the bootloader.

Re: Trying to rescue 32 TQFP mounted on PCB

Posted: Sun Sep 28, 2014 10:37 am
by mightyohm
It is hard to accidentally change the fuse bytes. What were the symptoms? Did the board stop responding to your programmer?

Re: Trying to rescue 32 TQFP mounted on PCB

Posted: Sun Sep 28, 2014 11:29 am
by englund
Yeah, it stopped responding to the programmer. I have tried 3 different programmers (USBASP v2.0, Arduino UNO as ISP, AVR-ISP-MK2) on 3 different computers (win7 32&64 bit, ubuntu) and also tried to apply an external 1MHz clock but nothing worked.. I checked with a logic analyzer (USBee AX PRO) that the programmer signals where being sent correctly, but the MISO-line was always silent from the atmega.. :(