1) Finally screened and etched the SSOP24 breakout widget. This is needed so I can breadboard the chip and find its magic.
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| SSOP-24 breakout. Toner transfer method is surprisingly efffective. |
2) I worked up a shift-register backpack for the LCD screen. I figured since 4-bit uperation of the LCD screen requires only 7 pins, why not control them with a shift register and reduce the micro pins count by four? why not indeed. We will soon-ish see if this is wise or dumb, but I tossed together a simple interface board to help test.
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| You can see the evidence of a sloppy laser printer: the ground pours are splotchy because the printer is too. |
3) I'd always planned on an LED Meter bridge backpack to hold the actual control ICs. I had assumed something like the TLC5940 sinking the rows and a 595 through high-side transistors on the columns. Trouble for me is, I don't see a great way to control the TLC5940 without using more pins than I have available... so I'm falling back to plain shift registers. I'd already made the LED meter board with plan A in mind, so I'll be driving columns no matter what. unless I remake the board.
Here's the backpack, it'll hold one 74hc595 to fire seven transistors for the cols, and then two TPIC6B595s to sink the rows.
4) I drilled and tinned all of these, and began populating the meter backpack. The tinning ain't pretty, but it seems to work well.
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