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 Posted: Apr 17, 2012 - 11:44 AM |
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Joined: Apr 23, 2009
Posts: 13
Location: Dhaka, Bangladesh
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Hi all,
Recently i am working with Atmega128A mcu. At first i didn't know that it's ISP PIN are different from the other avr mcu's (like... mega32 or mega88). While browsing through this forum i realized that it is PE0 and PE1.
Now my question, Is there any option to change the ISP pins to regular MISO and MOSI pins (i.e. PB2 and PB3). |
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Posted: Apr 17, 2012 - 01:30 PM |
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Joined: Oct 05, 2006
Posts: 2242
Location: Poland
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No RSTDISBL, no fun!
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Posted: Apr 17, 2012 - 02:09 PM |
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Joined: Apr 23, 2009
Posts: 13
Location: Dhaka, Bangladesh
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then i have to cut my tracks...  |
_________________
With best regards
Mahmudur
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Posted: Apr 17, 2012 - 05:12 PM |
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Joined: Jul 19, 2011
Posts: 460
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mahmudur85,
Don't feel too bad, you have company. I fell into the same "trap" a few years ago on one of my early AtMega projects. Now, I check the data sheets carefully on any "new" (i.e. new to me ) AtMega chip I use to make sure I know which pins are used for ISP porgramming.
It seems to me that some of the AtMega & AtXMega data sheets do not clearly & concisely state the ISP programming options available for a given chip. I forget which chip it was but I was led to believe from the data sheet that I could only program it via JTAG or the single-wire option ("PDI"?). So I wired my PCB for the JTAG port and it worked fine; but later I discovered I could also program the chip through the SPI signals. I reread the data sheet and could not find any mention of this SPI-ISP capability.
I'd be a happier Atmel customer if the data sheets would include a chapter dedicated to ISP programming. The chapter's first section should clearly state which programming options are available for the chip and which pins are utilized. |
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Posted: Apr 17, 2012 - 05:29 PM |
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Joined: Apr 23, 2009
Posts: 13
Location: Dhaka, Bangladesh
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Quote:
I'd be a happier Atmel customer if the data sheets would include a chapter dedicated to ISP programming. The chapter's first section should clearly state which programming options are available for the chip and which pins are utilized.
very much agree... but still atmel data sheets are very helpful..
--
mahmudur |
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Posted: Apr 17, 2012 - 07:46 PM |
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Joined: Oct 05, 2006
Posts: 2242
Location: Poland
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mahmudur85 wrote:
then i have to cut my tracks...
No, if you own a (I hope) QFP-64 zif external programmer. A bootloader can use just about any pins for self-programming. Even the ones you have mistakenly used. Actually only fusebits are unself-programmable.
If it is a batch of 10000 PCBs then this is an option. If those are 100 PCBs - do not bother with bootloader. But indeed, as this gotcha is quite popular, search and perhaps you will hit some SPI bootloader suitable for the task and compatible with ISP, but with a custom pin mapping. I would be surprised if you didn't find such thing in here.
Good luck! |
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No RSTDISBL, no fun!
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