HP97 The journey begins

[Harald]

(07-21-2019 03:13 AM)teenix Wrote:  

(07-20-2019 07:29 PM)Harald Wrote:  Looks good! Fingers crossed there are no big issues with it!

Adding to the uphill battle, sadly there is :-(

As hard as I tried, even with flux paste, about a third of the PCB pads for the IC's will not take to the solder with the chips in place. This has never happened before so not sure why. Also some of the chips I ordered had wider pin spacing to the ones in the data sheet. I think I can just get can get away with this, but as they are so small, it's a fiddly fix.

Very frustrating so had to take a break. All I can think to do is clean the pads thoroughly and try wetting them with solder before placing the chips.

I also played with the Classic anode driver timing by shifting the point where the 5 data lines are written by about 1uS and the display seems fine. Due to the PIC's internal hardware, it takes 3-5 instructions to sense the clock reference. Then 3 more to recall and output the data to the anode driver (total average 875nS). I triggered on the falling edge of PHI_1 and that caused it to stop working, so a bit too early. However, this timing delay works ok after the falling edge of PHI_2 which is quite late. I settled on the rising edge of PHI_1 and the data is output just after the falling edge of PHI_2 which is somewhere in between. Not quite exact and a tiny bit of jitter, but it seems happy.

cheers

Tony

Hi Tony,

If you like you can send a kit (I'll pay for it) and I can try assembling. My address has changed and I am not sure if you have the new one already, so please make sure before sending anything...
I had to play with the timing on the display driver as well. I can't remember what I settled on (I could look it up if you like). But the display did not work initially when I triggered the DMA on the clock edge I expected to be correct.

Cheers,
Harald