Sorry to open yet another AVR lockout recovery thread, but I have not been able to solve the problem on my own.
First of all, I have an Atmega 1284 for which I built a devboard myself (using this scheme: http://avrprogrammers.com/atmega1284bd.php).
I used the board fine (MCU set to use internal clock source at 8mhz, xboot++ boot loader, 5v supply and an Olimex ISP500 for initial programming) until yesterday, when I found an 16Mhz crystal oscillator (rectangular, 4pin, I'm not talking about a simple crystal) and decided to try it.
The oscillator is a recovery from some 20y old board and I couldn't test it (my oscilloscope can do 5mhz max) and couldn't find a datasheet either (the model is Motorola K1148B, with 16.00Mhz written on top of it), so maybe it's malfunctioning. Yep, after all it was not a very good idea to rely on it...
Anyway, now the damage is done: I flashed my MCU with the following fuse settings
- LOW 0xE0 (which should set the clock source to Ext. Clock, Startup time 6CK + 65ms)
Sadly, now the 1284 does not startup anymore, either without (which is expected) or with the oscillator connected. My ISP programmer (Olimex ISP500, used with avrdude) doesn't want to program the device either.
So, supposing that the oscillator IS working:
1) Anything bad in my fuse configuration that i might have overlooked?
2) Can a slow startup time of the oscillator cause my ISP programmer to timeout when trying to program? (the ISP500 starts powering the circuit when the programming begins, i think...)
Supposing the oscillator is NOT working:
1) I'm trying to obtain a few newer oscillators at various frequencies (1Mhz, 8Mhz and 16Mhz). Should the old oscillator be the problem, is sufficient for me to plug the new and working one in the board and to get my atmega working again?
2) I tried supplying the clock to XTAL1 using the ISP500 (it has a fixed 62.5Khz clock source on pin 3) but i was still unable to connect to the device. Do i need to slow down the programming to get this working? (tried -B 200 in avrdude, but nothing came out of it... got some more flags to try?).
The bottom line is that i want to get my Atmega1284 working again, and learn something in the process. Advice is appreciated ;-)
Thanks for taking time to read this and sorry for my English. I'm not a native speaker. :)