PiGraham
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Re: Adafruit LCD on 8bit interface

Fri Sep 05, 2014 5:34 pm

notro wrote:The BeagleBone Black 4" LCD cape has an onboard 74AVC32T245: 32-bit dual supply translating transceiver with configurable voltage translation; 3-state
It is used on all the LCD signals, and since both the display and the BBB works at 3.3V it doesn't act as a level shifter.
What's the purpose of this arrangement? To clean up the signals? (your display also has a 74LVC245, but the purpose here is level shifting)

Some Beagle boards run 1.8v I/O so I guess the shifter is to allow the cape to work with other models?

notro
Posts: 695
Joined: Tue Oct 16, 2012 6:21 pm
Location: Drammen, Norway

Re: Adafruit LCD on 8bit interface

Fri Sep 05, 2014 10:07 pm

PiGraham wrote:
notro wrote:The BeagleBone Black 4" LCD cape has an onboard 74AVC32T245: 32-bit dual supply translating transceiver with configurable voltage translation; 3-state
It is used on all the LCD signals, and since both the display and the BBB works at 3.3V it doesn't act as a level shifter.
What's the purpose of this arrangement? To clean up the signals? (your display also has a 74LVC245, but the purpose here is level shifting)
Some Beagle boards run 1.8v I/O so I guess the shifter is to allow the cape to work with other models?
Thanks, I wasn't aware of that. So the purpose is level shifting.

Ref: http://elinux.org/BeagleBoard_Hardware_ ... 1.8V_I.2FO

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mwilliams03
Posts: 122
Joined: Mon Oct 29, 2012 2:56 pm
Contact: Website

Re: Adafruit LCD on 8bit interface

Sun Dec 28, 2014 8:29 pm

Hi
I've been watching this thread with interest.
How are hard is it to change Peter's code to a 16bit parallel write?

I have been experimenting with some basic GPIO macros and I can get a 320x480 display to update in 70ms, via 16 parallel write on a B+. However I want to go faster.

A copy of my code can be found here;
http://ozzmaker.com/piscreen/PiScreen-16bitParallel.c
I compile with -O3 option.
Mark -- OzzMaker.com -- Creator of;
+ BerryIMU
+ Berry GPS-IMU
+BerryGPS-GSM
+ PiScreen - A 3.5" TFT for the Rasspberry Pi

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peepo
Posts: 305
Joined: Sun Oct 21, 2012 9:36 am

Re: Adafruit LCD on 8bit interface

Fri May 22, 2015 4:50 pm

Is there a clear simple write up anywhere?
cannot find introduction for Raspberry Pi.

8bit digital interface looks to be a great alternative to SPI,
ie SPI is already being used.
though it does look quite a beast.

Is it included in Device Tree?
or maybe not needed?**

thanks again

Jonathan

**this looks like DT notation:
https://github.com/notro/fbtft/wiki/Performance#itdb28

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