Recently I have bought the Raspberry Pi 2 along with a small 3.5 touch screen. It works fine and I'm more or less happy with it (there is some choppiness in the rendering of things (even the cursor is moving in a choppy manner) but from what I've read this is due to it not using the HDMI port, which provides GPU acceleration). However now that I also want to add some extra functionality through various sensors I'm facing the issue that comes from the way its pin connector is designed - it covers all pins from 1 to 26:
1, 17 3.3V Power positive (3.3V power input) 2, 4 5V Power positive (5V power input) 3, 5, 7, 8, 10, 12, 13, 15, 16 NC NC 6, 9, 14, 20, 25 GND Ground 11 TP_IRQ Touch Panel interrupt, low level while the Touch Panel detects touching 18 LCD_RS Instruction/Data Register selection 19 LCD_SI/TP_SI SPI data input of LCD/Touch Panel 21 TP_SO SPI data output of Touch Panel 22 RST Reset 23 LCD_SCK/TP_SCK SPI clock of LCD/Touch Panel 24 LCD_CS LCD chip selection, low active 26 TP_CS Touch Panel chip selection, low active
Since I'm pretty new to this kind of thing (and electronics in general) I'd like to ask you guys for some help. Basically what I want to do is figure out which of those pins are indeed required by the display (and its touch module) so that I can free the rest by simply detaching the display and using jumper wires move it to a breadboard or just leave it hanging somewhere (but still able to actually use it). I'm especially interested whether it really requires 2*3.3V + 2*5V (all in all 16.6V) since I need to have as many free power pins as possible. I was unable to find any datasheet whatsoever hence I really don't know the power consumption of this thing. I have a multimeter at hand but I haven't got the slightest idea where to start (especially since I fear I might damage either the LCD display, or the RPi2, or both). I have read here (see answer by tinylcd on Tue Aug 19, 2014, 5:20AM) that such a display draws just 3.3V from the Pi. If it's indeed so - awesome! Further the answer here explains that for a 7 inch touch display by Sain Smart you require only a single power pin with 5V.
From the description in the table above I can deduce the following:
Note: I'm using this useful interactive diagram to see which pin does what.
- It requires a GND (hence 1 GND pin is out)
- 1 or (hope not) more power pins
- Some of the NC pins (clock? I2C?)
- Pins 11, 18, 19, 21, 23, 24 and 26
- Possibly pin 22 (reset)