10
4.10 LCD display
4.10.1. Serial interface LCD: (the jumper is placed on the 2 right-hand pins of J23)
The Alice EduPad incorporates an HCT595 shift register (U6) to control the LCD display. The
chip select for the HCT595 is P6.7 of the MSP432 LaunchPad.
The U6 outputs QA-QH as the control and data bits D0-D1, D4-D7 for the LCD.
The pinouts of J1 are as follows:
Pin 1
GND
Pin 2
VCC (5V)
Pin 3
Connect to GND via the VR1 for contrast adjustment
Pin 4
QA
(D0)
RS pin for LCD module
Pin 5
GND
Write only for LCD module
Pin 6
QB
(D1)
EN pin for LCD module
Pin 7
Not used
Pin 8
Not used
Pin 9
Not used
Pin 10
Mot used
Pin 11
QE
(D4)
DB4 pin for LCD module
Pin 12
QF
(D5)
DB5 pin for LCD module
Pin 13
QG
(D6)
DB6 pin for LCD module
Pin 14
GH
(D7)
DB7 pin for LCD module
Pin 15
Via a 100 Ohm resistor to VCC
LED backlight for LCD module
Pin 16
Backlight ground
EN/DIS for LED back light
The HCT595 is connected to the LCD controller with QE ~ QH to DB4 ~ DB7,
QA to RS, QB to enable. The QC and QD are not used.
The LCD module is hardwired for write-only operation.
4.10.2. Parallel interface LCD: (the jumper is placed on the 2 left-hand pins of J23)
The Alice EduPad also incorporates a parallel interface for the LCD, the P3.6, P5.2, P5.0 and
P4.6 are connected to the D4-D7 of the LCD via a 74HCT245 buffer (U18). The control pins are
P3.0 for LCD R/S and P6.7 for LCD EN.
4.11 Digital-to-Analog Converters (DAC)
The MCP4725, a 12-bit I2C DAC is installed for learning I2C communication.
It converts a digital binary code to an analog signal so a program can generate different
waveforms from the DAC.
The DAC
’s analog output is provided on the J32, labeled as DAC. One way of testing the DAC
driver is to connect the DAC output to an ADC input, so a user can send a binary code to the
DAC and read the code back from the ADC.
