Parallel GLCD with 20-pin PIC

[jpanhalt]

I got the mechanics/math for my inclinometer working earlier in the week and have temperature, tilt, and re-zero working in simulation.

Today I turned to my graphic display. It is a New Haven Display, NHD-12864MZ and uses the KS0108 controller. The PIC's I have available are the 16F690 and 16F1829. Both are just 20-pin devices.

It appears most people use a single port to drive the display data pins DB0-DB7. I have assigned PortC to that. Six pins are needed for control functions, but I do not have 6 pins on the same port for doing that.

Plan:

1) PortA pins RA0,RA1, RA2, and RA5 will control chip select (right/left halves of LCD, 2 pins), register select, and enable.

2) PortB pins RB4 and RB6 will control reset and read/write select.

3) PortB will be set before setting PortA. PortC (data) will be set last.

Does that plan make sense? Would you divide the control pins differently?

Note: USART uses pins RB5 and RB7, MCLR is RA3, and clock out is RA4. The datasheet is pretty skimpy.

Thanks,

John

 

[Jon Wilder]

You could use a 74HC595 SPI to parallel latch chip to drive the LCD's parallel port. Only would require 3 pins on the PIC to drive that (SDI, SCK and Latch). If the PIC doesn't have a SSP port, SPI is simple to bit bang.

 

[3v0]

Better yet get a faster PIC with more PINS and memory.

 

[Pommie]

Sounds like you're making a serial GLCD. If so, let me know how your display works (CS1/2 = active high/low etc.) as I have lots of code for that display.

Mike.

 

[jpanhalt]

Yes, I am making a serial GLCD, but with a twist -- I need some decoding of the serial data. I have captured PWM data from an accelerometer with a 12F683, and converted it into digital data for tilt (signed) and temperature. The critical part of the serial link will be a pair of xBee's, which will be decoded by whatever chip is attached to the GLCD.

I could get a 16F877, 40-pin chip, but that would take until next Thursday. More important, I have never worked with a graphic display. My only experience with any display was with a serial Parallax around the first of the year. I have 16F1829 and 16F690 20-pin chips in my parts box and figured it would be a good learning experience to use one of them. In theory, at least, 20-pins might do everything I plan to do for now. I am pretty certain the final project will have a larger chip.

My question is simply what is the best way, if there is one, to divide up the 6 control signals between my available 4-pin (RA) and 2-pin (RB) ports.

Thank you for the code offer. You can be certain I will take you up on it, but right now, I would like to play with the display to get a better understanding of how it works rather than just making it work with someone else's code.

Regards, John

 

[be80be]

Put the data on portc and the controls lines on portb and 2 of them on porta ra4 and5 and that leaves you 3 I/O ra0 to2 and one pin for input ra3

But you need two of the port B pins rb5 and 7 for serial Hope you don't want to use more then one ADC pin then

I would put the LCD on one chip and make it in a serial backpack

 

[Jon Wilder]

The 16F887 would be the better choice over the 877/877A. On chip oscillator and a few other added features (the F877/F877A is becoming obsolete).