serial LCD needs delay?

kdoggfunkstah

I purchased the serial lcd from parallax and I've been testing it out interfacing it with a pic microcontroller.
I wrote code in order to send characters via the uart in the pic. When I first tried to run this, it shot out garbage, except for the first few characters. I played around and tried to put in a delay between each character and it fixed the problem. However, the specs do not mention this and I would like to not have this delay due to the large amount of time it takes to update a whole screen.
Can anyone help me out with this one? Thanks!

Jon Williams

There are some commands, like clearing the LCD, that do in fact require a bit of a delay -- this is a function of the LCD, not the controller. That said, remember that there is another host processor that has to take your commands and then deal with the LCD, so adding a bit of pacing won't anything.

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Jon Williams
Applications Engineer, Parallax

kdoggfunkstah

I'm still a little confused... Is there a time required for the serial to parallel circuitry that comes with the module? I would imagine there would be a fixed time needed in order to convert the incoming serial data to parallel? Is there any specifications on this?
In my host controller code I have it so the uart does not send another data until the data is fully sent. Should there be a feedback from the lcd module that should tell my controller that it is safe to send another character?

Jon Williams

Can you post your source code? I think that would help us help you. And no, there is no feedback from the LCD. I'm sure that you just need to insert proper timing into a few key spots. I've written code for our serial LCD that runs on the SX micro; this is very similar to the PIC. If it works on an SX, we can help you get it working on your PIC.

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Jon Williams
Applications Engineer, Parallax

kdoggfunkstah

Here is my LCD initialization code:
void init_LCD()
{
PORTCbits.RC6=1;
Delay10KTCYx(51); // 100ms delay
putcUSART(0x0C); // Clear LCD Screen
while(BusyUSART());
Delay100TCYx(40);
}

and here is the current lcd output function:

void out_lcd(void)
{

// x position
// convert to ascii numbers
// send one by one
for(i=0;i<5;i++)
{
putcUSART(x_ascii); // put in array
while(BusyUSART());
Delay100TCYx(40);
}

// send to position 6 0x86

// y position
for(i=0;i<5;i++)
{
putcUSART(y_ascii); // put in array
while(BusyUSART());
Delay100TCYx(40);
}


// send to position 12: 0x8C


// z position
for(i=0;i<5;i++)
{
putcUSART(z_ascii); // put in array
while(BusyUSART());
Delay100TCYx(40);
}


// pitch
for(i=0;i<5;i++)
{
putcUSART(pitch_ascii); // put in array
while(BusyUSART());
Delay100TCYx(40);
}

// send to position 6, line2 0x9A

// roll
for(i=0;i<5;i++)
{
putcUSART(roll_ascii); // put in array
while(BusyUSART());
Delay100TCYx(40);
}

// send to position 12, line2 0xA0;

// yaw
for(i=0;i<5;i++)
{
putcUSART(yaw_ascii); // put in array
while(BusyUSART());
Delay100TCYx(40);
}
}



Thanks!

Jon Williams

Our serial LCD docs suggest a 5 ms delay after sending the clear screen (0x0C) instruction -- you don't have this in init_LCD.

And I'm not much of a C programmer, but your numeric conversion routines don't seem to use the loop index to point to an individual character within the array.· For example:

void out_lcd(void) {
· // x position
· // convert to ascii numbers
· // send one by one

· for(i=0;i<5;i++) {
·· ·putcUSART(x_ascii); // put in array
·· ·while(BusyUSART());
·· ·Delay100TCYx(40);
· }

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Jon Williams
Applications Engineer, Parallax