ATMega644P Anyone?

Topics related to the HV Rescue Shield:
http://mightyohm.com/hvrescue2
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chris.burkart
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Joined: Wed Jul 27, 2011 8:20 am

ATMega644P Anyone?

Post by chris.burkart »

I just got me one of these HV rescue shields thinking I could just match the pins from the 28 pin ATMega328 to a 40 pin ATMega644P. I was able to read the fuses successfully but not write them.

Am I wasting my time?

Chris
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mightyohm
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Re: ATMega644P Anyone?

Post by mightyohm »

Chris,

I've never tested the Rescue Shield with the 644P, but based on a quick review of the datasheet, the parallel programming interface is very close or identical to what is implemented for the ATmega88/168/328P. It's possible that there are some subtle differences in the command format or timing that are causing issues, but it should be possible to make it work. The fact that reads work is very encouraging, that means you are really close. Have you tried writing various fuse values from 0x00 to 0xFF to the part to see if there is any dependency on the data you are trying to write?

Can you post a schematic, diagram, or table showing how you connected the pins on the Rescue Shield to your 644P?

Jeff
chris.burkart
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Joined: Wed Jul 27, 2011 8:20 am

Re: ATMega644P Anyone?

Post by chris.burkart »

I did try a few different fuse values. Didn't seem to matter much. Read but no write. Pin configuration below. I read over the datasheets too. Seems like it should work.

ATMega328 Pin# ATMega644p Pin#
3 15
4 16
5 17
6 18
11 19
12 20
13 21
1 9
25 40
9 13
8,22 11,31

7 10
20 30
14 1
15 2
16 3
17 4
18 5
19 6
23 7
24 8
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mightyohm
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Re: ATMega644P Anyone?

Post by mightyohm »

chris - I haven't forgotten about this, but have been on travel the past week - I'm away from my lab so I can't do any testing, but I'll poke around in the datasheets and see if I can find any issues.
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mightyohm
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Re: ATMega644P Anyone?

Post by mightyohm »

Chris,

This week I was finally able to procure an ATmega644P for testing. I am able to read and write the fuses just fine. I tried reading and writing several fuse values and each time had no issues setting new fuse bytes and reading them back.

I checked (and re-checked) your hookup table and it looks good. I hooked up exactly the same connections on a breadboard and double-checked them with the datasheet for the 644P and the Rescue Shield schematic, just to be sure. (One minor difference, I didn't tie pins 8,22 and 11,31 together externally, I wired 8->11 and 22->31).

A few things might help us get to the bottom of this:

1. Can you confirm you are using an Atmega644P and not a 644PA? (It's not that the PA won't work, just that it might be one reason why you are getting different results than I am.)

2. What fuse values are currently programmed into your Atmega644p, and do the fuse values the Rescue Shield returns match your expected values? (Include EFUSE if you know what it is.)

3. Do you know if there are any lock bits set? This might be causing problems if so, I think fuse bytes are also protected by the lock bits.

3. What fuse values are you trying to program? The defaults (LFUSE=0x62, HFUSE=0x99) or something else?

4. Can you try to duplicate your results with another 644P, to see if it's just that one part that is causing problems?

Sorry it's taken me so long to get to this, I was on travel most of August and I am just now getting time to sit down in the lab with some real parts vs. just studying the datasheets.

Thanks for your patience.
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