ET Team AVR-Base ATmega128

[metal]

I have received this board since 3 years, and never succeeded making it work because I 've never succeeded programming it

Anyway, I removed the chip that came with it and have recently bought a new one to replace it, still I was unable to program it with STK500.

Later I made an adapter from AVRISP 6-pin to 10-pin header and tried using it to program ATmega128, it was saying that MISO pin is shorted. When looking at the datasheets of ATmega128, I noticed that PE0 (PDI) is connected to RS232 chip, and it is always driving this pin high.

The only solution in my eyes was to temporarily remove it off the board to be able to use STK500 to program ATmega128. Does any owner knows a way where I can insert a resistor between the output of RS232 chip and PE0 (PDI) pin in order to prevent it from disturbing the programming process.

BTW, there is a new version of this board which fixed this problem, note R5~R7 used to isolate it from the controller:


Just thought I should share this piece of info here because it took me ages to figure out what the problem was!!

I attached mein to show off with SMD soldering skills 

thank you for reading.

[pickit2]

looks like they added JP1-JP4 to select Port or RS232.
also a nice upgrade to voltage regulator too.

[metal]

still it was annoying that I had to remove the RS232 chip to enable ISP programming. I am thinking about a bootloader now...

[solutions]

Umm...what about just lifting the Vcc pin on the RS232 chip instead of the whole device?

You might be able to power it off one of the IO pins on the micro...if not, you can deadbug a two pole jumper on top of the RS232 and wire one side to the pad and the other to the lifted pin.

[h0nk]

Umm...what about just lifting the Vcc pin on the RS232 chip instead of the whole device?

You might be able to power it off one of the IO pins on the micro...if not, you can deadbug a two pole jumper on top of the RS232 and wire one side to the pad and the other to the lifted pin.

This would work for older TTL-Gatters (74xx).
But im afraid that the RS232 is some sort of CMOS on the logic pins.
The clamping diodes will then happily supply the current for the chip.

I would use a 10 k resistor between the TxOut of the RS232 chip and PE0 of the ATMEGA.
A small SMD resistor (0201 or 0402) will fit between the lifted pin and the pad.


Best Regards

[PaulC]

i also got one a while back for a project i was working on, ended up using a atmega2560 instead..
been stuck in a draw since, strange i was thinking about using it for a function generator, freq counter the other day..
interesting note about programming options..
would this still be a problem with avrisp programmer, if so i may look into h0nk ( I would use a 10 k resistor between the TxOut of the RS232 chip and PE0 of the ATMEGA.
A small SMD resistor (0201 or 0402) will fit between the lifted pin and the pad. )..

just done g00gle, found this interesting note :

http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=61406&start=0

[Mega32]

I think the schematic is here , for the one wo. jumpers
http://www.etteam.com/product/avr/avr-base-atmega128/ET-BASE%20AVR%20ATmega64-128_Schematic.pdf

And the manual (Thai) here
http://www.etteam.com/product/avr/avr-base-atmega128/%a4%d9%e8%c1%d7%e8%cd%20ET-BASE%20AVR%20%20ATmega64-128.pdf

The above avrfreaks url , says that it can be programmed via JTAG ... So do you have a Dragon or JTAGICEMKII , or even one of the old mega16 based clones ?

I seem to remember that Atmel recommends 4k7 (Atmel appnote avr042 http://www.atmel.com/Images/Atmel-2521-AVR-Hardware-Design-Considerations_Application-Note_AVR042.pdf .. Pg. 7/8 ) inserted between the programming pin , and an external device.
So lift the pin on the RS-232 chip , install a 4k7 from lifted pin to pad , should do it.

Else use suggestion about lifting the RX/TX pair connected to PE0/PE1 and installing 2 jumpers.




Btw: Do remember that the Mega128 has a factory enabled "Mega103 compatibility" fuse that you would always want to disable.

/Mega32

[metal]

I traced the track that should be cut, the area is very limited for an SMD resistor to be put.

I will go for a bootloader solution. This one:
https://sites.google.com/site/shaoziyang/Home/avr/avr-universal-bootloadere
seems excellent, I tested it couple of years ago and it worked OK.

[nooknikz]

Manual (r3)

http://www.micro4you.com/files/atmega128/Manual-BASE-AVR-ATmega128-r3.pdf