Simple Reverse-Engineering of a Nanox NDM082 Sanyo LC7985NA LCD Module

Electronic Goldmine is selling the Nanox NDM082 LCD for a low price ($2.49 G17746) because they don’t have the specs or hookup info. Normally, a comparable module would sell for $8-$10 retail or maybe $5 if a reseller had the datasheet.

A 14-pin connection is apparent in the photograph, which I reckoned matched the standard for most alphanumeric character LCD display modules. They all use 14-pin or 16-pin connectors, either straight or in a pair of rows.

Even if this particular LCD part sells out, the information in this article will be useful for exploring and connecting other LCDs.

Nanox NDM082 Compact 2x8 LCD Module with Backlight Nanox TW 2294V 0 NDM082 Sanyo LC7985NA LCD

Nanox TW 2294V 0 NDM082 Sanyo LC7985NA Compact 2x8 LCD Module with LED Backlight.

When examining an unknown part, the first thing I look for is the widest trace. That’s the copper line etched on a PCB (printed circuit board) that has been designed to carry the most electrical current. You’re likely to find two wide traces -- one for positive and one for ground.

Thick trace connected to frame

Thick trace connected to LCD frame is likely to be ground.

Ah ha! Here are a bunch of clues:

That’s likely to be ground. Even in low-voltage circuits, an engineer isn’t going to wire positive (hot) to an exposed metal location that a consumer or conductive material might touch.

I spotted another wide trace on the other side leading to pin 2 on the connector. That’s likely going to be the positive power supply pin.

Datasheet for Part Under Sticker

A search for Nanox datasheets was unsuccessful. The primary chip arrived covered with a sticker reading “315A”. Peeling the sticker off with a fingernail reveals a Sanyo chip, part number LC7985NA. Searching for the chip was much more fruitful. I found a comprehensive datasheet for the LCD controller driver.

Sanyo LC7985NA PDF

Fantastic!

That’s exactly what we need. The Sanyo datasheet includes voltage requirements, memory addresses, protocol, and commands. This chip conforms to LCD standards, and therefore should be drop-in compatible with commercially-available LCD products and open source code.

Continuity Mode

The next step is to match the pins on the controller chip with the pins on the LCD PCB.

Matching connector hole with chip pin using continuity mode on a multimeter

Matching connector hole with chip pin using continuity mode on a multimeter.

Set your multimeter to measure resistance (ohm, Ω). Many multimeters include a buzzer that sounds when the resistance gets near zero ohms. This is called continuity mode.

With the circuit powered off, starting with the first unknown hole on the connector, touch the tip of one multimeter probe to the hole. Then, slowly drag or touch each pin of the known chip. When the buzzer sounds (or the resistance drops), you have found an electrical connection between the external connector and the chip.

By repeating this process for each hole on the connector, you can map the chip pins to the connector holes. Let’s see what the pinouts are for the Nanox LCD...