A display is a display is a display

I happen to have on hand a DL1414: a 4-character, 16-segment LED display. It has the advantage of a small footprint which will take up only a little space on a breadboard. There is a variation of it available from DigiKey (search for “HPDL-1414”). Since this is probably a little pricey, I’ll also show how to hook up typical N-character by N-line parallel and serial LCD displays. These are cheaper and more readily available. I’ll be looking at other display technologies in the future, but these should cover the ‘simple’ requirement for this project. (NOTE: You can substitute 2×40 displays without code mods. 2×16 and 4×16 will require some character addressing mods.)

A Reference Schematic

Display Schematic

This schematic includes the 3 display types that I will be discussing. It is not intended to use all three displays at the same time as this schematic might suggest. Just match the signal names between the PIC and your selected display and connect only those lines and use the appropriate software file. That way, the provided program should run the device.

DL1414

DL1414 Photo

The DL1414 requires 7 bits [D6:D0] for character data (upper-case alpha, numeric, and punctuation). PORT B is used for this [RB6:RB0]. RB7 will be used for the WR strobe. The 2 address bits [A1:A0] we’ll put on PORT C bits RC7:RC6. The video explains the function of these signals.

20-Character by 4-Line Parallel LCD

Optrex Photo

This display will use all of PORT B [RB7:RB0] for character/command data. We’ll also use PORT C [RC7:RC6] for RS and R/W. The E line will come from PORT C [RC2] where it will be out of the way of the serial comm, PWM, and ADC ports we’ll be using later.

20-Character by 2-Line Serial LCD

Newhaven Photo

Only one line from the PIC is required to drive the serial LCD display [RC6]. Even though this is an “RS-232” interface, the RS-232 logic levels are not required. The PIC and the display are so close to each other that large signal swings used for long distance transmission are not required. This is the easiest display to connect to your PIC and, if the USART is not required for other devices, it’s going to be the solution I use for connecting a display.

The code (assembly & C), schematic, and some other stuff are included in the following project download file:

Download PWM-ADC Project: pwm_adc_code.zip




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