I built a programmer about a year ago, and it served me well with several PIC projects. Now I wanted to experiment with the ATmega328, so I built the AVR adapter and I have some strange issues. I have no experience with AVR chips, and don't know the 'default' behavior when new.
The fact that the mounting holes in the suggested PC adapter are at the other side of the connectors had me confused for a while, till I realized the holes seem to have no function.
First I checked all connections and everything seems ok.
I have two different AVR chips. One marked ATmega328P-PU, one ATmega328P U (both literally) They responded somewhat differently:
Chip marking
ID
Lock
FUSE
FUSE High
FUSE Extra
ATmega328P-PU
1E950F
0xFF
0x62
0xD0
0xFF
ATmega328P U
1E950F
0xCF
0xFF
0xDE
0xFD
The 328P-PU program area is read as random data, and different each read gives different values, giving the impression that the data is floating.
The 328P U program area seems to have code (boot loader?) at the end (from 0x3e00 and up. Which could explain the 0xCF in the lock bits.
So... questions:
-Is this normal behavior for new chips? (i.e. can the unprogrammed area give random readouts?)
-The '328P U' marking seems suspicious. I found no reference anywhere to this. Anyone?
-The oscilloscope shows minor overshoots on the signals from the chips (about 0.2V). I don't think this has any influence on things though. The ground connections seem Ok.
-According to the datasheet, AVCC should be connected. On the adapter PCB it isn't. Problematic?
-The adapter circuit shows a jumper for use with 20-pin devices on the 28-pin sockets. The PCB doesn't have that.
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-New chips are usually blank.
-No problem with small overshoots.
-Sure, connect AVCC.
-PCB was not updated; should be ported to Kicad but I have no time.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I built a programmer about a year ago, and it served me well with several PIC projects. Now I wanted to experiment with the ATmega328, so I built the AVR adapter and I have some strange issues. I have no experience with AVR chips, and don't know the 'default' behavior when new.
The fact that the mounting holes in the suggested PC adapter are at the other side of the connectors had me confused for a while, till I realized the holes seem to have no function.
First I checked all connections and everything seems ok.
The 328P-PU program area is read as random data, and different each read gives different values, giving the impression that the data is floating.
The 328P U program area seems to have code (boot loader?) at the end (from 0x3e00 and up. Which could explain the 0xCF in the lock bits.
So... questions:
-Is this normal behavior for new chips? (i.e. can the unprogrammed area give random readouts?)
-The '328P U' marking seems suspicious. I found no reference anywhere to this. Anyone?
-The oscilloscope shows minor overshoots on the signals from the chips (about 0.2V). I don't think this has any influence on things though. The ground connections seem Ok.
-According to the datasheet, AVCC should be connected. On the adapter PCB it isn't. Problematic?
-The adapter circuit shows a jumper for use with 20-pin devices on the 28-pin sockets. The PCB doesn't have that.
-New chips are usually blank.
-No problem with small overshoots.
-Sure, connect AVCC.
-PCB was not updated; should be ported to Kicad but I have no time.