Tuesday 13 January 2015

how do you solve a problem like a green dot?

Belfryboy Clone green dot logger When the "green dot" problem arose I was at a loss as to how to fix it. But that half the fun.  Then we found the solution. Several in fact. Torkelmj uses a novel method, by programming an Atmel ATtiny microprocessor to behave like a Dataflash chip with the correct security register the Davis console will open its communications port.

But this was not satisfying for me. I wanted to still use the logging abilities. WXforum member Travisc came up with another solution using a PIC to fool the console that then turned itself off and enabled the logging chip once the console was happy.
traviscs solution, very elegant
This was all very well, but still not what I had in mind, but with some collaboration the solution arose. The algorithm used was cracked by comparing genuine logger security registers and the Belfryboy logger was reborn.

All I needed was a way the program the chip.

I initially I started to program the chips using a buspirate in SPI mode and an SO8  ZIF socket. The security register was calculated in Excel and then flashed into the chip. This worked most of the time, but not always.

I tried in vain to write the code to use an arduino board to program the chips, JoeBean beat me to it!

It was then just a case of putting his code on to my fixture and voila, I had a fairly foolproof method of quickly programming the chips.
The finished programming fixture.

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