Articles tagged “LCD”

I have currently been using some terminal emulation software on my PC to see the output of the Z80 computer. It seems a little silly to rely on a large multi-gigahertz, multi-megabyte machine just to display the output from a machine at the megahertz and kilobyte end of the scale. I had previously done some work with a dsPIC33 to drive a 320×240 pixel graphical LCD so dug out its breadboard and dusted off the code to try to make something of it. Inspired by John Burton's recent experiments with PAL TV output I decided that the first thing I should do is add support for TV output.

Comments dsPIC33 VDC dsPIC33FJ128GP802 Electronics LCD PAL PG320240H-P9 PIC Spinning cube TV

In a previous entry I mentioned that I had purchased a PG320240H-P9 graphical LCD. This is a 320×240 white-on-blue pixel display, and it does not have an on-board controller or RAM. To display something on it you need to constantly refresh it with picture data; in this instance, sending four pixels at a time, starting from the top left and working from left to right, top to bottom — a bit like the scanning pattern of a CRT monitor. Connecting a circuit to the LCD is made slightly more tricky by its use of a 16-pin 1mm flexible flat cable.

Comments dsPIC33 VDC dsPIC33FJ128GP802 Electronics LCD PG320240H-P9 PIC Spinning cube

LCD Timing
Last time I discussed the hardware I mentioned I had LCD timing issues. I have finally resolved them, but this has been the most time consuming part of the project so far. The first thing to sort out was the LCD's E pin. Once you have set up the LCD's input pins to a state where they're ready to read or write data, you need to drive this pin high. I had had some success by holding it high permanently and relying on the Z80 to set all the other to the right state at roughly the same moment, but this was inaccurate and resulted in occasional display glitching.

Comments Electronics Emerson LCD PG12864LRS Z80 Z80 computer

A computer needs some way of interacting with the outside world via input and output devices. It's about time, then, that the Z80 computer project acquires a section dedicated to I/O. The Z80 differentiates between memory and I/O devices, though both share the data bus and the address bus. You can control I/O devices using the in (input) and out (output) instructions. When you input or output you must specify a device address and a value or target register. For example,
in a,($20) ; Read a value from device $20 and store it in A.

Comments Electronics LCD PG12864LRS Z80 Z80 computer

I enjoy dabbling with low-level programming, but have never actually built a computer to run these programs. I think it's time to correct that, and as the BBC BASIC project has required me to develop an almost complete Z80 OS (the only thing that's left for the TI-OS to do is manage files) I thought a Z80 computer would be a good start. The planned specs are (as a starting point):
10 MHz Z80180 CPU;64KB RAM (2 32K×8 SRAM chips);128KB Flash ROM;Graphical LCD;Simple joypad input;Keyboard input (AT using either software AT routines or dedicated microcontroller).

Comments Electronics LCD PG12864LRS PICAXE PICAXE-28X1 Z80 computer

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