Confused about 644 vs 644p

Hi all,

I am attempting to build a version 1.3a Sanguinololu and am very confused regarding the type of atmega chip that should be used. I pulled the git repo from [github.com] and used parts.txt to order all my parts from my electronic supply.

Parts.txt version 1.3a lists:

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IC2 ATMEGA644-20PU ATMEGA644-20PU DIL40 atmel

So that is what I brought. Now all the information I read from other places seems to imply that I should have brought a 644P. could someone please clarify which is the correct chip to use? From what I was reading someone was saying it is impossible to use the 644 because it lacks the second usart?

I got as far as trying to write the bootstrap to the 644 but I fear I may have ruined the chip. I was following the instructions on the wiki and set up the fuses as so (changing 644p to 644):

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avrdude -p atmega644 -C 'C:[path to avrdude.conf]\avrdude.conf' -c dapa -P lpt1 -U lfuse:w:0xFF:m -U hfuse:w:0xDC:m -U efuse:w:0xFD:m

this command executed successfully but since then I've been unable to communicate with a chip. Has this command ruined the chip?

My final question was regarding the practicality of the Sanguinololu overall. it seems to me that after paying for the printed circuit board, the FT232RL, the 644 (not to mention 2 of them to get the right one) the cost is already close to $35US which is already $7 more than a fully functional Arduino Mega AVR ATmega1280-16Au board. Is this project actually necessary, and should there be a warning to newcomers that they would be far better off simply going for a prebuilt ATmega board? are there advantages that I am not seeing to using the Sanguinololu?

An Arduino can't control a RepRap on its own; it needs a RAMPS shield. Either this or the all-in-one Gen6 is likely to cost more than DIY (Sanguinololu or Gen7), but the difference is small enough that choosing ready-made makes sense if you value your time.

If you check the wiki there is an up to date parts list on the Sanguino page. It list the correct 644p and everything else. Just pick up another. You can not control a RepRap with an Arduino alone. Nor can you do it with a bare Sanguinololu board. You need to add 4 Pololu or StepStick stepper motor drivers. This adds an additional $45 or so to the cost of the board. This brings the total price to around $100 which is still $60 less than a RAMPS setup.

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Charles Gantt.
Build blog [themakersworkbench.com] <---- my personal site
Build worklong [www.thebestcasescenario.com]

Thanks for your response! So I take it from your answer that the 644P is required, and the 644 wont cut it? Maybe its worth updating parts.txt in git so noone else will make this mistake in the future?

I'll order a 644P and continue with the Sanguinololu since I've already got most of the parts. I'd still love to know if the fuse command above has hosed the 644 chip, because if not there might be something wrong with my parallel port programmer...

Someone else will have to comment on the fuse settings bricking the chip. It may be fixable with some high voltage programming (google it).

I will export the current list and will ask Joem to update the git.

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Charles Gantt.
Build blog [themakersworkbench.com] <---- my personal site
Build worklong [www.thebestcasescenario.com]

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So I take it from your answer that the 644P is required, and the 644 wont cut it?

Both chips are equally suited for RepRap purposes. The P model uses less power (like 0.2 watts instead of 0.5 watts) and features a second serial port - which isn't used.

However, the 644 and 644P have different signatures, so you better use an appropriate bootloader. These instructions for a Gen7 should work on a Sanguinololu as well: [reprap.org]

That said, one person reports success with a 644P bootloader on a 644. Just proceed as if your 644 were a 644P and don't try to use the second UART.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY