HP97 The journey begins
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05-03-2019, 06:33 AM
Post: #68
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RE: HP97 The journey begins
Hi all,
Making slow progress. I created a linear power supply for the CPU module for testing purposes with 3.7V, 5V and 6.2V, and the calculator runs ok. The card reader seems to write ok as well. I tested the cards with 67 and 97. The whole system seems a lot happier. Still having read problems however, even on a HP CPU board. On reading old posts I changed the 47uF cap across the switched Vbatt on this HP CPU board but no luck. Maybe I'll try the ones on the reader board. I could not find a reference to the cap value across the card motor. Anyone know what it is? It looks like 10-22uF tantalum or so by the size of it. The new CPU board has Murphy's luck built in somewhere I'm sure. It was reading only on the second card pass from power up and fail all other times. I looked real closely at the data changes during a read and I made a very small code change to the read software. I didn't expect much, but to my surprise it started reading every time except for the very first after a power on. There was actually no data change on RA RB for this read so a bit confused. It will read after a card write after power on, so it may be a variable not initialised properly. Maybe that cap across the motor needs a kick start to get going properly ?? cheers Tony |
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