Objective Development Forums

First off, I'd like to ask you to excuse me for complaining about issues I'm having with a derived AVR Doper.
I'd also like to say thanks, so :Thank you, Objective Development, for creating V-USB and making it available under the GPL as well.

Moving on, I programmed the Atmega8-16PU (to put it on this slimmed down AVR Doper) with a parallel programmer (with the help of an additional board I will use later for the Avr Doper) and I could get Windows to detect the Lite AVR Doper (both HID and regular).

However, I haven't found the 74HC126N and had to use a SNHCT125N instead.

I tried to program an Atmega8-16PU with the slim AVR Doper and the LED lights up for a second and AVR Studio says : Entering programming mode.. FAILED!
The programmer is set as STK500 (and AVR studio connects to it without problems). Avrdude doesn't work either (avrdude -c stk500v2 -P avrdoper -p atmega8 is what I used to check if it works in HID mode and it seems to be ok - same errors as the ones described in the V-USB readme).

What I have checked so far (so that these settings/possible mistakes/things to check are excluded or corrected, if something is wrong):
- the Doper's AVR was flashed OK with Bascom AVR (the check said it was ok, no differences were found)
- the continuity of the ISP cable
- the ISP connectors are wired properly - 5x2 both on the AVR Doper and on the mini-board which holds the Atmega8 socket)
- the Doper isn't wired in a wrong way or anything - it is an etched PCB
- the to-be-programmed AVR is powered properly at 5V, AREF, VCC and AVCC ( should AREF not be fed with power? )
- the target AVR has a 12Mhz quartz with 22p capacitors wired to the ground (should it be left quartz-less? )
- the mini-board (the one used for programming the initial AVR via the parallel port) was also used here
- the AVR's signature came out as invalid in AVR studio
- Avrdude was also used to test regular mode and then used for HID mode as well
- the used OS is Win XP SP3, HID and regular worked ok (device detected and everything)
- all contacts were checked for short circuits and unwanted connections between them
- I tested the programmer with two different Atmega8 chips, one was brand new, one was used before, same thing
- none of the parts heat up, so there isn't a short circuit
- I swapped the SNHCT125N with another new SNHCT125N, nothing changed

The setup: Slim AVR Doper - ISP cable - mini-board with a 28 pin socket which is something like this: GNDs are connected together; +5V goes to VCC (with a capacitor) and AREF, AVCC; SCK, MISO, MOSI, RESET are connected to the right pins on the socket.

Any help would be appreciated as I've spent a lot of time making sure it wasn't some kind of soldering or wire related issue. I wouldn't have asked for help if I hadn't tried most things already. Maybe it's something obvious I've missed, being unable to see the forest because of the trees.

Thanks in advance.

You did notice that there is a difference between the HCT125 and HCT126? The former has inverted enable pins while the latter has non-inverted ones.

If you can't find the HCT126, you may try AVR-Doper with the USBasp hardware. This is a compile-time option. This hardware works without an external driver.

christian wrote:You did notice that there is a difference between the HCT125 and HCT126? The former has inverted enable pins while the latter has non-inverted ones.

If you can't find the HCT126, you may try AVR-Doper with the USBasp hardware. This is a compile-time option. This hardware works without an external driver.

I did take a look at the data sheets but I missed that somehow.

Thank you, I will try to replace it as soon as possible and let you know how it worked out.

Later edit: I can't just tweak it and turn it into USBasp because I etched it and it's just like that mini-AVR Doper PCB.