I have a 20x2 in one box. I am using a 7 wire cable from the box to another to handle a LCD (+,-,signal) and three inputs, which is 6 of the the 7 wires. My board has 4 general purpose outputs. I am pretty sure it is wired for all four to be outputs, but I don't recall. I have one wire left and basically no space left in either box for much more electronics. I have also used almost all of the pins on the 20x2 and the two left I am saving for expansion.
My idea was to have a status indicator for my system using a bicolor LED and two output pins from the LCD (green means program running, red flash means alarm, off means program off).
I have a tricolor laying around, but seems like overkill since I only have the three states (and I couldn't use the all of the colors anyway since my outputs are simply high/low). I would also have to confirm I have four working outputs and not two. However, it is a good alternative.
From the LCD manual:
On power up, all outputs are at a high impedance (configured as inputs). As each output is addressed,
it is taken out of the high impedance state. The initial high impedance state permits the user to use either pull up or pull down resistors to avoid “bounce” when the processor is powered up.The current (source or sink) by any output should be limited to 15 mA.
From Picaxe Manual 3:
Bi-colour LEDs often contain both green and red LEDs connected in ‘inverse parallel’.
This means if current flows one way through the device the LED lights green, and if
current flows the other way the LED lights red. Therefore by using the sink/source
capabilities of the PIC Microcontroller it is possible to light the LED in both colours.
If I understand the above then it should work right? If not, can I damage my LCD pack by trying this (if I use the resistors westaust55 suggested)?
