iowarrior 40 and backlight

[watts]

The LCD module I bought for my project requires an inverter. I am pretty comfortable building one of these from some parts I got at the surplus store:

http://www.allelectronics.com/cgi-bin/i ... AMPS_.html

It will take some time to find the connectors for this thing, and in the meantime I want to play with my new toy (and write the software) What should I hook up (or not hook up) to run the iowarrior without the backlight?

I'm asking because leaving p0.2 unconnected results in no display. (but no smoke either)

Also, where should the power jumper be? I have tried all three locations. There are no obvious wiring faults and Prober sees the unit. And my binary counter works fine.

It looks like this inverter will draw 500ma which is probably more than the USB bus will support, but I will cross that bridge when I get to it.

Thanks
watts

[Guido Körber]

Set the power jumper according to the amount of current you draw. Likely the LCD will not use much, so 100mA will be good.

Though if your inverter really draws 500mA you should get the power for that from an external source.

One of the most common reasons for not seeing anything on a LCD module is a wrong contrast voltage. If it is an alphanumeric module you should at least see faint rectangles of pixels as soon as you apply power to it. If you don't see them your contrast voltage is way off.

[watts]

OK, re-reading the data sheet has answered the jumper question.

I've left for work, but did not see any squares at all, so maybe I need to back up a little: using the schematic on page 26 of the IOWarrior data sheet, I am connecting the pin 2 and pin 15 of the LCD to Vcc on the IOWarrior board, and pin 1 to the GND on the IOWarrior board. I have left pin 16 free for now. I am then sending data using IOWarrior Prober as specified on page 26.

All the LED's lit up when I first did this, but I have since disconnected the jumpers.

The 10K pot is hooked up as specified, and I've tried both ends and the middle. But no squares!

It sounds like I should check for wiring faults. Be back tomorrow.

[Guido Körber]

If the LEDs light up you did something seriously wrong. Likely you did send the data to the wrong interface.

Pin 15 and 16 of alphanumeric LCDs are usually used to supply a LED backlight. You should not connect them if you have EL backlight.

If you have power and the pot properly connected to the LCD you should turn the pot slowly until you see the rectangles. If they do not appear there may be something seriously wrong.

[watts]

After much painstaking solder-joint checking, I figured out the prolem: it was the 10K pot. Either it's defective or it's the wrong impedance for my particular flavor of display. Pulling pin 3 of the display module to GND (by shorting the two pins of the pot) gives acceptable contrast, I will tweak it later with a new pot.

In the meantime, I've won over my skeptical wife with a special version of "hello world"

Thanksgiving is saved....!

watts