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Interface an LCD with a Microcontroller

NewHaven 2x16 LCD Display, Part Number: NHD-0216BZ-RN-YBW-ND

Datasheet pinouts are meant to be written in a way to skim quickly and gather necessary information. However, due to a couple different reasons, the PHYSICAL pinout is not necessarily in the same order as the datasheet pinout

Facing the display, this is the actual ordering of the pinouts

14|13|12|11|10|9|8|7|6|5|4|3|2|1| 15|16

Pin Symbol Description
14 DB7 MPU, 4 high order D bus lines
13 DB6 MPU, 4 high order D bus lines
12 DB5 MPU, 4 high order D bus lines
11 DB4 MPU, 4 high order D bus lines
10 DB3 MPU, 4 low order D bus lines, not used in 4-bit mode
9 DB2 MPU, 4 low order D bus lines, not used in 4-bit mode
8 DB1 MPU, 4 low order D bus lines, not used in 4-bit mode
7 DB0 MPU, 4 low order D bus lines, not used in 4-bit mode
6 E MPU, Operation En. Signal, Falling edge triggered
5 R/W MPU, Read/Write Select,1: Read 0: Write
4 RS MPU, Register Select, 1: Data 0: Command
3 V0 Adj Power Supply, for contrast (~0.6V)
2 Vdd Power Supply, Voltage (+5V)
1 Vss Power Supply, Ground
15 Vss Do Not Connect
16 Vss Do Not Connect

MPU just refers to what you connect this pin to, in this case our PSoC microcontroller.
V0 is a resistor divider or potentiometer that controls the contrast of the actual display.

Using PSoC Board to Interface

V0 can be controlled using a voltage divider circuit using vdd from the MPU such as a 10k & 100 ohm resistor setup

Always use a bypass capacitor between the LCD power pin and Vssd digital ground on the devkit
Why? Smooths the input signal in the event of fluctuations and prevents weird behavior/bugs

4-Bit Mode

We will be designing our circuit to use 4-bit mode as opposed to 8-bit mode to save output pins on our MPU/MCU & for simplicity

  • We only need DB7-DB4, which are physical pins 11-14
  • R/W (pin 5) can be controlled, or wired to GND (logic 0)
    • We only really need to write (R/W 0) to the lcd, not read (R/W 1)
  • RS?
  • E?

Custom Firmware

IDK if the Psoc Creator LCD Component in the Components Catalog is compatible with my display and I might as well learn, so I will be writing my own drivers, firmware whatever you want to call it, for the LCD

Initalize the Display

Must send 3 wake ups before switching to 4-bit mode commands This is because generally LCD's with only 4 wired MPU lines requires us to ensure that we can communicate to the LCD that we want to operate in 4-bit mode even though it default's to starting in 8-bit mode.

Function set 0x30 | 0011 0000

001D is db7-db4, bottom 2 bits are the most important
xx1x, DB5 must be set to 1
xxxD, DB4 holds the Interface data length control bit, 1 means 8-bit bus mode, 0 means 4-bit mode\

  • Essentially this is the signal to select the mode for the display

NFxx is DB3-DB0, top 2 bits are the most important
Nxxx, DB3 holds the Display line number control bit, 1 means 2-line display mode, 0 means 1-line display mode
Nxxx, DB2 holds the Display font type control bit, 1 means 5x11 dots format, 0 means 5x8 dots format

void init()
{
P1 = 0;
P3 = 0;
Delay(100); //Wait >40 msec after power is applied
P1 = 0x30; //put 0x30 on the output port
Delay(30); //must wait 5ms, busy flag not available
Nybble(); //command 0x30 = Wake up
Delay(10); //must wait 160us, busy flag not available
Nybble(); //command 0x30 = Wake up #2
Delay(10); //must wait 160us, busy flag not available
Nybble(); //command 0x30 = Wake up #3
Delay(10); //can check busy flag now instead of delay
P1= 0x20; //put 0x20 on the output port
Nybble(); //Function set: 4-bit interface
command(0x28); //Function set: 4-bit/2-line
command(0x10); //Set cursor
command(0x0F); //Display ON; Blinking cursor
command(0x06); //Entry Mode set
}