LCD 117 (Not 118)

[chopperwalker]

Searched all the net and this forum so sorry if it's a repeat...

I came across a brand new LCD 117 kit from a friend who uses arduino. Before starting assembly I did a lot of reading realizing the baud rate issue (this kit runs at a fixed 9600). I have an 18X which I understand I can use setfrq to get to that speed. However, I read on another forum that there is a start bit issue which results in jumbled characters on the screen. Does anyone have any insight on the potential problems here? Can I simply overclock or will I have the same serial communication error?


Thanks,

Chopper

P.S. I noticed that on Anderson's site that you can order preprogrammed 16fs to controll these. Anyone know if the pic could simply be swapped with one that runs at 2400 (like in the 118 kit)?

 

[hippy]

This is probably a "signal polarity" issue. The PICAXE's initialises their outpt pins low which works with Nxxxx baud rates but is opposite to the idle polarity when using Txxxx baud rates. This can cause the first data byte to be be mis-read by a receiver.

When using Txxxx baud rates, the recommended practice is to make the output line HIGH and add a suitable length PAUSE at the start of the program.

 

[JoePage2008x2]

Hi, is it the 117 kit from Phanderson, i bought that kit to use in my GCSE project and it works perfectly, but i had the same problem as you.

Do this as a test, note i used a 28x

setfreq m8
pause 12000  ` do this pause so it has time to load
serout 7,T9600_8,("?f")   ` reset screen
        pause 10
        serout 7,T9600_8,("  Hello  ")  ` display hello
        pause 10 ` always included a small pause between instructions

When i first tried it i used N9600_8 not T9600_8 this is what your problem may be, check out his datasheet, that helps.

 

[chopperwalker]

Thanks for the input. I ended up ordering just the PIC programmed for 2400 baud.

I noticed that the 118 kit ships with a 4mhz resonator. I'm not as familiar with resonators, but I know it affects the clock speed and its accuracy. The 117 kit doesnt have the resonator.

How can that affect my setup?

Will there be more inconsistencies when transmitting data?

Or will have just have to give more pauses after send commands?

 

[Andrew Cowan]

The 117 kit chip has an internal resonator. That's fine - it just means that you can't put the 2400 baud chip in the 117 board - it won't work as it needs the resonator.

A

 

[BeanieBots]

Assuming that a resonator is NOT required, it should not affect anything.
Using the internal oscillator simply means that timing will not be as accurate as it would be with an external resonator.
The internal resonator frequency is affected by both voltage and temperature. If it drifts enough to make comms fail, you might be able to make things good by tuning OSCON. (not an option if your PICAXE uses a resonator)

I have a serial LCD which simply fails when ambient goes over 30C due to oscillator drift.
Unfortunately, it's driven by an old 28X, so the only option I had was to hand pick a resonator for the 28X. The problem is still there but I found a resonator which would keep it working up to 36C which is rare enough for me not to be concerned.