serial lcd with 16f628

[dragons_fire]

Im having lots of problems getting my serial lcd to work properly. the screen is a matrix orbital lcd4021 set to 2400baud (i think) and im using a 16f628 as a controller.. i have just started to learn this stuff, and i dont know that much about it. i have been learning by just looking at examples on the net and reading this site. i have attached the code below. if anyone can help, it would be greatly apreciated.

@ device INTRC_OSC_NOCLKOUT
cmcon = 7
TRISA = %00000000
TRISB = %00001000

lcd VAR PORTA.3
baud CON 2400

Pause 4000

start:
SerOut2 lcd, baud,["hello world"]
Pause 1000
GoTo start
End



thanks; dan

[Bruce]

In the back of your PBP manual you can find a chart showing Serin2/Serout2
baud modes.

baud CON 2400 creates a constant value named baud which = to 2,400.

SerOut2 lcd, baud,["hello world"] is not going to give you 2400 bps inverted.

SerOut2 lcd, 16780,["hello world"] ' would.

You could opt for something like this rather than using the numeric value for
2400 inverted mode with Serout2;

baud CON 16780 ' Create CONstant baud which = 16780.

SerOut2 lcd, baud,["hello world"]

[dragons_fire]

thanks Bruce. i didnt know that i was doing that wrong, although i realized i have another problem too.. i have been trying to change the baud rate on the screen, however i cant seem to do it, so it should still work at 19200 baud as long as i use the correct number from the book (19200, Driven, Inverted, Even*, 24608) right??? so i would put "baud con 24608"... so my other problem is, how do i change the internal osc of the 16f628? and if i change it, do i need to change the baud #???

thanks
dan

[Bruce]

24608 will give you 19200, driven, inverted, even parity, but I doub't you're going to get solid results with the internal 4MHz osc.

Are you sure the serial LCD you're using requires "even" parity? You might want to try 16416 for 19200, driven, inverted, no parity? I've never used the Matrix Orbital serial LCD's, but the ones I have used require no parity.

The internal 4MHz osc doesn't provide a stable clock for any timing critical stuff like serial communications, and, Serout2 probably isn't going to work reliably at 19200bps with a 4MHz clock (if it works at all).

See the **'s next to 9600 & 19200 in the Serin2/Serout2 Mode Examples chart with the note at the bottom stating ** Oscillator faster than 4MHz may be required?

Just assume it's never going to be 100% reliable with 4MHz at any data rate showing the **'s next to it.

The internal osc is for non timing critical apps. It will drift & it's not always super precise to begin with on the older 16F62x series. Newer parts with 1% internal oscillators normally work really well, but not some of the older series.

The internal osc isn't a good option for "reliable" serial comms for sure, and definitely not for data rates that are already marginal at 4MHz.

You can use DEBUG for 19200bps with a 4MHz osc, but it may or may not be reliable with the internal osc.

DEFINE OSC 4
DEFINE DEBUG_REG PORTA
DEFINE DEBUG_BIT 3
DEFINE DEBUG_BAUD 19200
DEFINE DEBUG_MODE 1 '1=inverted, 0 = true

how do i change the internal osc of the 16f628?

Not sure what you mean by this. You can switch from the default 4MHz to 37kHz by clearing PCON.3.

If you want to use an external crystal VS the internal osc, then see Melanies thread here http://www.picbasic.co.uk/forum/showthread.php?t=543

and if i change it, do i need to change the baud #???

No. You should use whatever baud rate the LCD data sheet states. Just be sure to use an oscillator speed that supports the baud rate, or switch to another command that supports the baud rate at the osc frequency you're using like the DEBUG example above.

[dragons_fire]

thanks again. in my last post i thought that the internal osc could be changed, but then i realized that it wont go above 4mhz anyways... i changed to a 10.000mhz external and changed the code a bit, and it seems close, but its still not working, and im still not sure what im doing wrong... im getting a lot more digits displayed on the screen, and it displays every 2 seconds like it should from the code.


cmcon = 7
TRISA = %00000000
TRISB = %00001000

lcd VAR PORTA.3
baud CON 24608

Pause 4000

start:
SerOut2 lcd, baud,["hello world"]
Pause 2000
GoTo start
End

thanks for all the help
dan

[Bruce]

Insert DEFINE OSC 10 & be sure to set HS in config word.

[dragons_fire]

ok, i think my only problem now is trying to get it to display something on the second line, instead of just wrapping the text... i want to be able to specify where it is displaying certain info..

thanks
danny

[Bruce]

That really boils down to getting familiar with the LCD's data sheet & commands available.

Looks to me like;

SerOut2 PORTA.3, 32,[254,"D"] 'would turn off auto line wrap

Then;

SerOut2 PORTA.3, 32,[254,"G",1,2] ' would let you position the cursor manually, and should put you on column #1, row #2?

[dragons_fire]

thanks bruce... i was actually just playing around with the different commands, i got it to clear, turn on and off, change the contrast and stuff like that... thanks for all the help, i think i have finally got it now...

danny