the hell of PCA9698

Here we go with the continuation of our doom story. In the previous blog I told you that Manes would test the i2c with his logic analyzer. And he kept his promise here are the results.
First of all he'd checked the SCL/SDA signal level/transitions with respect to the i2c general and PCA specific specification. It seemed to be ok except that some ACK didn't arrive, as it had to be in the read process. This was odd and suspicious. In the process of testing with the only good PCA he made a mistake in putting 12V on the inputs. So guess what another chip fucked up !

But more important he tested his bit-banging algorithm on a simple PCF and all signals appeared like in specifications. Conclusion is clear the PCA output chip was also fucked up earlier together with the input PCA. The ordering of 2 new PCAs and one extender is now in progress. We expect to test again with the new chips till the end of this week. This time we take things gradually no doubt about that.

In fact the reason why all chips were fucked up isn't yet totally clear in my opinion. When I first connected the NGW to the IO board, the chips were just soldered on the board and didn't see any of supply. At that time we had already the voltage drop. (1V) So the question here is what caused this drop ? It's true after the uncertainty of all that I started to play with board and did some measurements (eg. capacity); which in fact were not that smart. So it could be that in the process of all that some of the chips suffered badly of unwanted supplies. Nevertheless the previous question remains. I definitely want an answer on that. Maybe things become clearer when we replace the components gradually. I propose replacing in following order and test via bit-banging assembler program:

PCA output
PCA input
Extender

Suppose that after replacing all components everything is working back again than possibly the reason of malfunction was that one chip was already broken before the initial testing with the NGW. But these are speculations for the moment so I leave this conclusion till the end of the week. If tests with 8bit debug AVR went well, I can test with NGW linux bit banging algo's. If these work I finally can build the domotics. If these don't work I probably have to make changes on the existing bit banging algo or considering writing my own device driver from scratch.

In order to remove the two smd PCAs from the board a special suction tool is needed otherwise the board will be irrevocable damaged. This tool, I can use from the firm I work for luckily. I will take some shots of before, while and after for the blog because perhaps it will be a point of change in our luck so far.