Re: UDRC Compatibility with the 'Official' 7 inch touch screen display

Richard - VE7CVS

Thanks, John!

I did some further digging into the Raspberry Pi site, and found this:

If you are using a A+, B+, 2, or 3, then the display uses i2c-0 (also used for the camera and HAT configuration) up the DSI flexi cable. It does NOT need the two jumpers off the SDA and SCL pins on the display board to be connected anywhere. i2c-1 is therefore still available for your use.

If using a model A or B, then i2c-0 was not wired through the DSI flexi, and you do lose i2c-1 to the display. No, you can't share with other applications it as it is being used from the GPU side and there is no arbitration between the processors over access to the peripheral.
I'm using a Pi 3, and haven't been using the jumpers, but had assumed (incorrectly!) that the DSI link shared I2C with the GPIO connector. It does not.

Ah, found the datasheet - it might be helpful if the 'UDRC' tab on the main page pointed to the datasheet as well, I didn't think to look on the 'Products' page. I did look under 'Support', another place that I would normally expect to find documentation and schematics.

Now, it's time to plug this stuff together and see what works!

I'm happy to see the on board regulator for the Pi and display - powering these from USB has been problematic - had to find some micro-USB cables with heavier gauge wire to keep the Pi from sagging under load. Powering from the UDRC will be quite welcome!

- Richard, VE7CVS

On 8/13/16 10:50 AM, John Hays wrote:

On Aug 13, 2016 10:07, "Richard - VE7CVS" <ve7cvs@...> wrote:
> Can the UDRC be installed on a Pi 3 that has an 'Official' touch screen connected to the DSI connector?

> The display connects to the SDA and SCL (I2C) leads on the GPIO (pins 3 and 5). Will this interfere with the UDRC?

You don't need those pins.  And shouldn't wire them. You only need power and the DSI connector. You can use the USB input or 5v off the GPIO.

We have many units setup this way.
> Have the schematics for the UDRC been released yet? I couldn't find them on the NWDigital website or in the files area.
The schematic is on the data sheet which can find under products UDRC.
> - Richard, VE7CVS

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