Well here we are again back at the MPCD this seems like "The Neverending Story", oh well here goes. I had originally specified the MAX6955 LED display driver IC. A problem came up and it appeared to only support Charlieplexing, a technique to use fewer wires to drive your LEDs.
New Analysis: As I have previously stated that this display is a mixture of both 7 and 16 segment displays. These displays are in reality are very small incandescent lamps1. Now since I want all the bell and whistles, ie lamp test, blink any or all segments and dim them. I guess I will have to write this driver for my self. The segments are clockwise: a1, a2, b, c, d1, d2, e, f. Now the middle, right to left: g1, g2. Now the rest, clockwise: h, i, j, k, l, m.
Below I have constructed a table to show which segments are light for any letter.
I will have to most likely to scrap the use of a hex to 7segment decoder and do it software as well.
Please note that the software below is not complete this is my rabid mined at 3 am. LOL And is far from being complete I still will have to rebuild the tables to add the Decimal Point(part of the display hardware), and dimming the display, this most likely will have to be a PWM signal generated from a local Arduino, etc. So this means I need 17 Select pins: 4 (hex lamps), 13 (7 seg lamps) plus the 25 Drive pins: (17 (hex)segs, 8 (7 seg) for a total of 42 pins. .
To implement a dimmer control I plan to use 4x an Octal Buffers with Tri-State outputs to the lamp segment I will then add a limiting resistor in series with the lamp segment to ground The Arduino PCM output will drive the gate control pins 1 19 on the 4 via a buffer to deal with the fan-out load as each SN74LS240 is two loads(pins 1 19 x 4 8 Ouch.
More Changes: The following information was acquired over a phone call to Wamco today:
This is in the header files:
This is the function:
* the 16 segment display font map and lamp images came from the MAX6955 datasheet.
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