Resolved by Rich!
Hey guys.
I'm having a little trouble with an LCD display I recently purchased. I have read through some of the posts on the forum to help me get this going, but I need a little more help. I have it connected to D12 going through a 5v regulator. Ground to ground, Vcc to Vcc, and SDA (which I believe to be RX) to a signal pin. It lights up but when I try SendSerial(d12, 9600, "Hello" ) nothing happens. I have also tried a different port and changed baud rates, no change.
Now I believe this is a serial (what I was after) and i2c compatable so it should work. I havn't found a data sheet for it yet but here's a link to it, if it helps. Any ideas what's going wrong, or even if this thing is compatable with the v4? I hope some one can help as I would love to get this working.
Thanks in advance. 
I feel that there is likely a contrast potentiometer at the back of the LCD control board that needs adjusting.
If you can communicate with the LCD already pull-ups aren't needed.
Communication is working so SCL and SDA are fine, as Jeremie said no pull ups needed and logic level should be OK at 3.3v signals (we know it is, it's working).
I can only think it's the VCC to the LCD that's the problem since the I2C port outputs a 3.3v VCC but the LCD asks for 5V.
I just ripped my LCD from Melvin (don't panic, it wasn't secure and Melvin needs an upgrade soon anyway). If I get chance I'll test my one out as I know it works on 5V perfectly and will see a difference in the 3.3V. If nothing else it will show if Steve's LCD display is faulty or not.
1. LCD connected to I2C port 3.3v, Ground, SDA and SCL - Unreadable display, backlight is fine but characters are too feint (in fact I couldn't see them at all)
2. LCD connected to I2C Port SDA and SCL, 5v regulator (EZ-Robot one) connected to D23 Vcc and Ground feeding LCD. LCD display works perfectly.
The LCD needs +5V to the Vcc. The EZ-Robot regulator works fine for the blue 4 line display at 80/255 backlight brightness (I didn't test higher) so it should have no problems with the 2 line display.
So, bottom line is, give the LCD display a regulated 5V supply and it should work fine.
Tony
Hurray :D. I had a feeling 3.3v might not be enough which was why I quiried it with Jeremie. Anyway, happy days it's working now :). One little thing though which is something Rich mentioned earlier. While testing this on K-9, his ping sensor servo is making a low level buzzing noise. It's not twitching, but sounds like it wants to. Other servos seem ok but they are well covered so it's difficult to hear anything, where as the ping servo is the only one that's exposed.
Why is that do you think?
When I was using it in Melvin the neck servos would go rather mad almost causing damage. Again, I don't know the cause, if it's been solved or if the V4 would even suffer with this issue.
But on I2C the issue was not present at all.
Has it only started since sending commands to an LCD?
When I had a similar issue it was on serial only and would only twitch when new commands were sent via sendserial. I don't believe the serial commands were the issue nor the sendserial control since nobody else has mentioned anything similar and the sabertooth uses serial.
In terms of the servo jitter, this is usually due to fluctuations in power. The LCD may be causing some voltage ripple on the power line. To remedy this you can try adding a large electrolytic capactitor (maybe in the 220-2200uF range) between VCC and GND on the LCD.
Since the Devantech LCD needs +5V it may pay to grab a 5v regulator and hook it direct to the battery, this may bypass the problem (it may not since it's still drawing from the battery but I know you don't like to solder - side note: I haven't forgotten your TIP circuit I just haven't got around to finding it yet).
No problem buddy. Probably a bit of a mix up my end too. Anyway all sorted now (pretty much). Thanks for the info about the jitter advice too.
@Rich.
I'll give running it straight off the battery a try tomorrow and let you know if it makes any difference. I'm not adverse to a bit of soldering, but your right, it's not one of my favourite activities ;). No problem on the TIP circuit dude. No rush.
This is mainly aimed at @Rich or Toymaker as I know you have used these displays. Could one of you be so kind as to give me a quick script example to display the battery voltage on the LCD05 16x2 display please? I tried the following but got a "False" message.
Code:
I'm a bit stuck as to what else to try. If you could give me an example I would be grateful as this would give me something to work from to hopefully display the time, date ect as well.
Thanks.
Code:
I've presumed the 0,1,4,12,19,30,230,31,255 part all leads up to text entry.
It will display anything you ask it to. However it looks like you got a little confused with the variable/GetVoltage part.
Code:
Thanks to everyone for all of the help that was offered.