74HC164 to drive a LCD panel

Does anyone have suggestions/experience with using an 8-bit serial-in, parallel-out shift register like the 74HC164 to drive a LCD panel? I have been using a LCD module in 4bit mode, and want to try something a little cheaper.

How about hints for using 2 of these in tandem for a 2 digit LCD? 3 in tandem for 3 digit?...

It would be useful to know how to use a SPI port on a tiny AVR w/ the shift register for driving a simple LCD display.

thanks to any an all replies

The AY0438 (Microchip makes it these days) works pretty well for driving LCDs. But rolling your own is fun and if done right can be very low power.

I've done the drive a shift register thing. Used CD4094, same idea as

74hc595 but cmos and works better at 3 volts. 4 of 'em will drive a 4 digit 7 segment lcd display and leave a few bits left over for colon or decimal points. The only tricky part is you need to generate an AC driving waveform in software. I just updated the shift register 60 times a second and made sure I inverted the output data every other time. At a reasonable clock speed, 60 hz is pretty simple to do with a simple timer interrupt.

Mark

sonos scrobe on the papyrus:

Use 74HC595 rather than '164. It is closer to SPI.

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John B

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Yes, you can easily drive a static LCD with daisy-chained HC595s. Be sure to write your firmware so that you keep the average DC voltage across the segements in line with the specifications (typically something like < 50mV).

Multiplexed LCDs are trickier- I think you'd need a pack of resistors and I/O that can be individually tristated.

Or just use a micro with an on-board controller (but that severely limits your choice of micro).

Of course there are a number of driver chips available, but they tend to be a bit expensive.

Best regards, Spehro Pefhany

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