20x4 LCD + IIC/I2C/TWI/SPI Serial interface

[AndreyB]

Found a KiCad module @ http://sylvain.fish.free.fr/kicad_lib/ - checked it into rusefi_lib

[kb1gtt]

Did you find a schematic symbol for this as well? Often the symbol will include things like pin names or the GND via's.

[AndreyB]

They say "No .lib : use display in kicad DEVICE librairie" (librairie because they are French)

[kb1gtt]

Got it. I see the default lib includes a symbol for an LCD with a backlight. It appears this LCD module does not have a back light. If you expect a back light, let me know.

[AndreyB]

Pins #15 & #16 are backlight power:

[kb1gtt]

The module only has 14 pins. Are 15 and 16 in the same line as the original 14? If so I can add them to the module, if not then I'll need to know where those pins are located. Then we can use back light symbol in the schematic.

[AndreyB]

Yes, #15 & #16 are in the same line.

Also contrast is controlled with a resistor - so, we need a resistor

I use a 2K resistor between GND and 3rd pin for contrast

see also http://rusefi.com/forum/viewtopic.php?f=4&t=481

[puff]

http://www.noritake-elec.com/uversion.htm

[kb1gtt]

Thin LCD with many options, found here. Also comes with a simulator so you can see what it looks like on your PC.

http://www.lcd-module.com/products/dog.html

I wonder how much these cost.

[rus084]

i have spi graphics LCDs .
First is little display from nokia 3310
Second from siemens but bad work

[AndreyB]

Question: how long could the wires for these 20x4 HD44780 screens could be? 4 feet? 8 feet? 12 feet?

[DaWaN]

Has to be tested I guess. For fast SPI lines it is not uncommon to have these fail on cable runs as short as 2 feet, but this interface can be run slower if needed.
As a good practice you should insert a series resistor with the "E" line to limit reflections / ringing. Series termination seems easiest/best in this situation.

[puff]

Crazy idea. I'd suggest double conversion: whatever protocol it uses to CAN (a separate chip in the ecu), then, on the screen side - back from can to the standard screen (or any other display device).

actually, we could make it even simpler: converter from this protocol to sort of serial over bluetooth, and an app for displaying info.

this way we would retain the benefit of displaying data even during ecu crash (thanks to external chip), and eliminate these wiring/emission difficulties...

[AndreyB]

It's not a crazy id'sea, but let's focus on figuring out the wiring limitations first

[kb1gtt]

Length will depend on the cable used. AKA flat ribbon cable is much different than twisted pair. I would suggest attempts to remote use twisted pairs found in Ethernet wires. That said and with the lower data speeds, i'd expect you can get 8 ft reasonably easily. But that's just gut feel, no data driven, just the gut.

[AndreyB]

I would suggest attempts to remote use twisted pairs found in Ethernet wires.

That's a cool idea, $7.5 shipped for 100ft and 8 wires is exactly the number we need