ISP with two AVRs on one board

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#1
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Hi,

I am working on a project with 2 mcus(mega162 and tiny26). They communicate with each other through an SPI bus(mega162 as master and tiny as slave). I want to program both mcus through ISP without removing them from the project board (both are on the same board). Any suggestions on how to do this? Is one ISP header with jumpers on reset (or/and other lines) sufficient?

thanks in advance,
Fotis

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zap358 wrote:
Hi,

I am working on a project with 2 mcus(mega162 and tiny26). They communicate with each other through an SPI bus(mega162 as master and tiny as slave). I want to program both mcus through ISP without removing them from the project board (both are on the same board). Any suggestions on how to do this? Is one ISP header with jumpers on reset (or/and other lines) sufficient?

thanks in advance,
Fotis

My experience is that jumpers on reset are just fine. Make sure that the 'unused' one is held in reset somehow, you dont want it to try and talk while the programmer is working on the other - that can be embarassing, as one of my staff found out one day! We have a board with four ATmega128 on it. We use a FET switch to select which one is being programmed and another to hold all the others reset at the same time.

John

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I've not tried it but will be facing a similar situation soon. I think a jumper/header to select the reset line should work.

In my case, the micros will be on separate boards. I plan on installing a serial bootloader on the main micro and a SPI bootloader on the second. I then plan to have the main send bootload data to the second from its serial port through the SPI. But, for the initial bootloader install, that will be done through standard ISP to each individual board.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net