Woodstock Low Power
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10-31-2017, 10:32 AM
Post: #29
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RE: Woodstock Low Power
Some intermediate news.
The second prototype is working and is built into an HP-27 calculator. Here some pictures. As you can see the board fits exactly below the display and no mm is left, and the case can be closed without problems. On the left the circuit with the 512k flash, PIC processor, two display drivers. Thanks to the drivers the display is now much brighter than shown in the HHC2017 prototype. In the new design the LED drivers are placed on the top and the RTC is mounted on the bottom side. The RTC chip is 1 mm too high and would not allow to be placed on the assembly side. This image on the right shows the additional effort to add the GPS module. It is working fine with the LP circuit. Six wires have to be connected to the keyboard anyway, only two additional for the GPS needed, but also the 3,3V supply has to be added. My working prototype soldered to an HP-21 board, currently running the HP-25 firmware. Software work is going on. Fighting with the compiler, which shows unspecific internal errors and obviously doesn't like the LP circuit. Bernhard That's one small step for a man - one giant leap for mankind. |
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