Friday, May 16, 2014

I2C driver for Sharp LM167511 lcd display

Recently I got into my hand this old digital phone.

The phone is part of a proprietary system of the early 90s, not so much useful today, but the display seems to be still useful, so I took apart it from the rest, and I begun to test its behaviour.
Display is branded Sharp model LM167511 and it is controled by the OKI MSM6262 chip.
The other 2 components present on the PCB are column drivers T6A39, not particulary interesting to control it.There's not a lot of documentation about this display provided by Sharp nor anyone else, and googling for its name you can only find an old post of a spanish guy asking if someone knows how to use it.
Using a multimeter and the datasheet of the OKI chip I mapped the chip pin on the control headers.

The most hard part has been understand how to use V5.
I thought to use it, in the same way I used to use V0 on the hd44780, the OKI chip expects a negative power on that pin! I got help on that.
But after that it was a piece of cake.
To control it I used an Arduino board and the following circuit:

The display has 7 lines of 16 characters each.
It also has a quite weird memory mapping. The followings are the first character address for each row:
and this some code I wrote to drive this display.
that's all.

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