LCD compatability 16Fxxxx - 18Fxxxx

[Rob]

I have been using 4*20 "standard" LCD displays with Flowcode 3 & 4 for a while and always found them easy to use. I used 16Fxxxx pic's and had no problems however I have a couple of projects that need a bit more eerom,ram, speed etc. so I got some 18F1450 and 18F2580 which on basic levels are pin to pin compatible with say an 16F72.
I expected the LCD / Flowcode to work the same but after a lot of trial and error I cannot get them to display on any of the LCD's I have ,but a 16F72,16F689 or 16F877 will display in the same circuit, same code etc. just pic type changed.
On scoping the O/P's I find the main difference is the enable (E) pin is only approx 0.5V and a poor square anyway, there is no short or extra load on the line, in fact I can O/C the pin and the O/P is still the same (I have tried six chips), I am using port C3 as a trigger pulse and to confirm program is running etc.

display test 16F72.fcf

(6 KiB) Downloaded 261 times

display test 18F2580.fcf

(6.5 KiB) Downloaded 261 times

I have attached two example files

For clarity I am compiling with sourceboost pro to hex, using Mplab to program with a PICSTART Plus (all latest firm and software installed).
For weeks I assumed it was something I was doing wrong and in a way I hope it still is (human error is always the most likely cause of problems) but I am at a loss so I am asking for your help

Regards

Rob

[Benj]

Hello Rob,

The fact you can get the LCDs working on a 16F and not on a 18F is telling me that the problem is likely to be with your configuration of the 18F device.

What crystal speed are you using on your hardware? Have you matched this value in your Flowcode project options.

Also what configuration values are you using via the Chip -> Configure menu?

A crystal over 4MHz will usually need the HS oscillator option, Watchdog timers and Low voltage programming should also be disabled.

If in doubt the 1 second flasher test will confirm if you have everything setup correctly for your system to work.

[medelec35]

When you go through your configuration settings. You will need to check Low voltage programming is disabled, especially if you are using port B for LCD display.
RB5 is used for low voltage programming, so if LVP is enabled, you would not be able to use RB5 for i/p or o/p

[Rob]

Thanks for the speedy reply but I am using 20MHz, HS, watchdog disabled and low voltage program on both programs,
I am "flashing" on port C pin 3 ,which confirms the program is running but I am using 50ms delay instead of 1 sec but the effect is the same

regards

Rob

[Rob]

Fantastic, I was looking at it and didn't see it, it was the low voltage program !!!!! had to be disabled,
well yet again you folks have not let me down, thank you so much I was starting to pull my hair out and there isn't much to start with


thanks Benji
thanks Medelec35

[medelec35]

Thats great!
Glad its working.
Thanks for letting us know.