HW-ClockTWO Alpha Board (blank ALL LEDs)

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PROBLEM :
1. To blank ALL LEDs, it is necessary to "disable" the Column Driver, IC U4, 
74HC154.
2. The control pins on U4 for this function are Pin 18 (G1) and Pin 19 (G2)
3. HIGH on G1 and G2 disables all LEDs, LOW enables all.
4. Presently, these pins are permanently grounded LOW.

SOLUTION :
1. Isolate Pin 18 and Pin 19 of IC U4 from Ground.
2. This requires a couple of cuts on the solder side, and one cut on the 
component side.
3. Verify with a multi-meter that these two pins are isolated from Ground.
4. Connect a wire link from Pins 18/19 of IC U4 to the micro-controller IC U3 
(ATMega) Pin 26 (PC3/ADC3)

Original issue reported on code.google.com by anoo...@gmail.com on 25 Nov 2010 at 8:49

Attachments:

• DSCN7135.JPG
• DSCN7133.JPG

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[deleted comment]

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Added control logic for this in init().

To enable:
digitalWrite(COL_DRIVER_ENABLE, LOW)

To disable:
digitalWrite(COL_DRIVER_ENABLE, HIGH)

To speed this up:
PORTC &= 0b11110111; // Enable col driver
PORTC |= 0b00001000; // Disable col driver

Original comment by wyojus...@gmail.com on 28 Nov 2010 at 3:09

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The MEGA can't sink enough to handle both grounds.  I've gotten much better 
brightness with PIN 18 on the Col driver grounded and PIN 19 on the Col driver 
going to PC3 (COL_DRIVER_ENABLE).

Original comment by wyojus...@gmail.com on 28 Nov 2010 at 10:10

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On C2 board, Pin 18 is grounded and Pin 19 goes to PC3 on AtMega. On C3 boards, 
this change must be implemented in the board design

Original comment by anoo...@gmail.com on 2 Dec 2010 at 4:25

• Changed state: Started

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Confirmed schematic changes on initial clock3.sch.

Original comment by wyojus...@gmail.com on 17 Dec 2010 at 12:38

• Changed state: Fixed