Serial LCD's

[EShatara]

I'm have inconsistant results when using a Serial LCD as a debug/development tool to tell me what's happening in my program.

I've homed in on:

+ Pausing for 1 second on powerup to all the LCD to stabalize
+ I pause for 0.5 seconds after a clear
+ If I direct the cursor to the home position (line1 or line2) I'll pause for
10ms or so to make sure the command is executed.
+I tried running at 2400 baud and have changed over to 1200 baud.

One frequent quirk is that I usually get a bogus character at the home postion
after powering up, clearing and sending the first "Message".

Seems I'm spending more time debugging the LCD display rather my code. :-(

Thanks for any experience you can share...Chris

[mister_e]

did you try to add
DEFINE CHAR_PACING 1000

at the program header to see what's happening

[EShatara]

Thanks Steve,

I've tried pacing after I posted my question. It has made a difference but I still get a garbled character on the very first access to the LCD. The code currently is:

DEFINE CHAR_PACING 500
..
Pause 1000
Serout 3,N1200,[254.1]
Pause 500
Serout 3,N1200,[254,20]
Pause 20
Serout 3,N1200,["Waiting For Cmd"]
Serout 3,N1200,[254,192,"Address = ",#UnitAddr]

The VERY FIRST time this code is executed, I will get a garbled character in front of the message "Waiting for Cmd". Can't for the life of me figure out what's causing it.

Not a big deal for what I'm doing but I would like to understand what is happening here.

Thanks..chris

[Dwayne]

Hello Chris,

Chris>>The VERY FIRST time this code is executed, I will get a garbled character in front of the message "Waiting for Cmd". Can't for the life of me figure out what's causing it.<<

Try sending two "Clear" statements in a row.

First guess is, the senquencing of the Serial data between the two systems. Bad grounds will cause this.

Dwayne

[EShatara]

That seemed to do the trick. I did however have to put in a 100ms pause between the clears.

Thanks...chris

[mister_e]

Pause 1000
Serout 3,N1200,[254.1]
Pause 500
Serout 3,N1200,[254,20]

hope this is not an error from you guy 254.1 or 254,1?

can you try
SEROUT 3,N1200[254,1,254,20,"first message",13,10]

what about now?!?

[Ingvar]

Hi Chris,

My guess is that your seroutpin is floating up to the point when you send the first character, this character will for this reason be garbled. You could either put a "LOW 3" before the first pause(1000), or you could add a pulldown resistor to the serial datapin. 10k would probably be enough.

/Ingvar

[EShatara]

I'll give this a try a little later on this morning. I have a scope so I'll attempt to see what's happening.

Thanks for the tip..

Chris

[EShatara]

Hi Ingvar,

The resistor did the trick. I really didn't see a difference in the signal quality using a scope but the display has been quite stable for the past day.

thanks for the suggestion.
/chris

[Ingvar]

Good to hear that it works.

Perhaps you couldn't see any difference because your scope acted like a pulldown. Some cheaper scopes have less than one mega ohm on their input.

/Ingvar