HD44780 question

[Mike - K8LH]

I'm looking. It must have been online because it's neither one of the copies on my hard drive.

If I remember correctly, they showed driving the SCLK pin with an RC delay to the RCLK pin (a 100 ohm resister between the two pins and a 200nf cap' on the RCLK pin). This allows data to stay in sync' instead of being 1 bit behind as would be the case if you tied SCLK anr RCLK directly together.

Unfortunately this wouldn't be a 2 pin interface because you would still need to drive the LCD 'E' line. I apologize.

I'll keep lookin' online for that data sheet.

Mike

 

[3v0]

Mike please do not spend more time on this unless you are interested. I am mostly fussing with it for fun.

In most cases a uC for a 1 wire interface would be my choice. But when you have SPI devices, the clock and data can be shared so the 595 is attractive.

 

[Mike - K8LH]

I am interested. I just hooked up an LCD to a PIC for the first time just a few weeks ago so the fascination hasn't worn off yet (grin).

As for a uC solution. You could probably use one of those 14 pin PICs in SPI mode just as easily as in UART mode. And you'd probably have a lot more capability (PWM backlight control, commands to "store" and "download" custom font characters, 4x4 keypad, etc.).

Mike

 

[3v0]

Great.

I have not been up to school to drill the board yet. I was playing with a setup that already had an SPI interface for digital pots. It is much along the line of what Bill posted (another thread) but I was using a 4 bit interface to the LCD. I am still thinking about it but am playing with IR for a while.

A while back I had fun with this inexpensive LCD. It is $2 or less from Electronic Goldmine G15318 and AllElectronics LCD111.

Wintek # WDC2401P-1GNNA. Module size: 4.25" x 0.79" x 0.3". Display size: 3.5" x 0.4". Built-in driver. 14 pin male header pins on 0.05" centers. Includes hook-up diagram

It has internal logic to control the contrast. The display is hardwired to use the 8 bit interface. It has a built in I2C interface but you have to do a mod to use it. The problem is that the wire you need to cut may or may not be hidden under a epoxy blob on the unit. On the ones I purchased epoxy covered the traces in question. Also the pins are on .05 centers. It does not use the HD44780. Yup, it is cheap for a reason.

A while back I built a 3 wire interface using 2 SOIC 74HC595s. This is my first SMD board.

]

I am interested. I just hooked up an LCD to a PIC for the first time just a few weeks ago so the fascination hasn't worn off yet (grin).

As for a uC solution. You could probably use one of those 14 pin PICs in SPI mode just as easily as in UART mode. And you'd probably have a lot more capability (PWM backlight control, commands to "store" and "download" custom font characters, 4x4 keypad, etc.).
Mike

 

[Mike - K8LH]

That looks incredibly nice and after looking at the data sheet I realize you did some pretty good detective work and design work too (grin).

Mike