mega8 vs mega*8 (DIP) pinout differences ?

Go To Last Post
6 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I was hacking along with an old mega8, then needed to use 2 discrete pwm so I decided to plonk in a mega88 I had around...

But it's not recognized by my programmer, nor with the usbasp. I plonked in a m168, and the same happend - not recognized - .... putting the m8 back in, and it's recognized!

My wiring is dead simple. 5V vcc, 10K pullup on reset, AVCC+VREF+VCC hooked, both GND grounded, and a few caps on VCC... The ISP connection doesn't have any pullups/down, and these pins are not used fro anything else either..

So, what's going on ? the datasheet shows these are pin compatible.. what am I missing ?

Author of simavr - Follow me on twitter : @buserror

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Does your programmer know about these new-fangled models?

Did you slow down your ISP bit rate to the speed proper for virgin AVRs?

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:

Does your programmer know about these new-fangled models?

A USBAsp used with avrdude (assuming 5.10 (the one that follows 5.9 ;-) is being used). If avrdude is being used explore Lee's suggestion with "-B".

As these are 88's is there any chance they were last being used with a Dragon/JTAGICE and are left in debugWire mode?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
what am I missing ?
It's not what you are missing, it's what we are missing! e.g. The output from the programming attempt. (Make it verbose).

--greg
Still learning, don't shout at me, educate me.
Starting the fire is easy; the hardest part is learning how to keep the flame!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Well, I didnt find the true reason for the problem, but I desoldered/resoldered most wires, and the problem went away.
It doesnt explain why the mega8 worked; that had me wasting a lot of time! I'd rather have something failing that something working only on sunday mornings :-)

Anyway, from my research the 8 and 88 are perfectly compatible and it shouldn't have happened, there are quite a few references to that at Atmel's, must have been a fluke

Author of simavr - Follow me on twitter : @buserror

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I've been swapping M8, M168, and M328s in my Arduino boards while working on the bootloader; they're all wonderfully interchangable.