Can I re-use the GPIO pins that are driving an LCD display?

Question

I want to ask if I connect the LCD display to the Raspberry Pi, the pins that the display uses to work, am I able to use them for other stuff?

For example, to connect 433 MHz receiver and have the display the same time?

Answer 1

According to the LCD specs the pin usage is as follows.

Pin Used        Spare
 1  3.3V
 2  5V
 3  --          gpio2 SDA
 4  5V
 5  --          gpio3 SCL
 6  GND
 7  --          gpio4
 8  --          gpio14 TXD
 9  GND
10  --          gpio15 RXD
11  TP IRQ
12  --          gpio18
13  --          gpio27
14  GND
15  --          gpio22
16  --          gpio23
17  3.3V
18  LCD RS
19  MOSI
20  GND
21  MISO
22  Reset
23  SCLK
24  LCD CS
25  GND
26  TP CS

There are plenty of spare gpios to connect a 433MHz receiver (it only needs one gpio). Of course if you have a A+, B+, or Pi2 there will be more spare gpios on pins 27 to 40.

The problem will be physically attaching any additional hardware. You'll probably need to solder wires to the underside of the pins as the LCD display will be blocking normal access.

Answer 2

I able to use them for other stuff at the same time?

Generally speaking that's a bad idea, especially if you want to run two protocols that are of a high frequency.

There are some applications of "abusing" one connection to transmit additional data, but the main point about this is that one frequency has to be considerably lower then the other. (It's possible to use the electrical system with 50 Hz (50 impulses per Second) to transmit digital signals of several 1000 Hz without disturbing the electrical system considerably.)

But no, you shouldn't do this, because:

• They will interfere with each other, giving each other strange, wrong data which will lead to even more strange errors, or they'd just stop working.

• They might not start at all or drain too much current and crash (or destroy) the Pi

• It's bad practice, even if it works you create a connection that has no logical reason, making adjustments of one device twice as hard, because you have to consider what might happen to the other device.

• I'm not sure if hardware is allocated exclusively though, maybe this is possible, but it really should not be.