Introduction: Live Reverse Engineering WiFi Modules

By Josehf Lloyd Murchison
About: I was born in Cornwall Ontario Canada my family followed my father’s work construction, to Mississauga and Toronto, Ontario. My father worked on famous construction sites as the Cornwall Sea Way, the Commerce …

I like to reuse as many working components I can. Although I am reverse engineering a printers WiFi this method works on many other devices.

Please; don’t just pull apart obsolete electronics, then expect to find the datasheets for salvaged components and modules on line. Beyond proprietary knowledge, the more obsolete the part is, the harder it can be to find a datasheet on that component.

Do what I do; first I find out if the machine runs. It doesn’t need to work like new it just needs to work enough to do diagnostics. Open it and see if you can find the datasheets for the components you want to salvage. And if you cannot find the datasheets for the components, reverse engineer them.

From this printer I wanted to salvage the WiFi module and the COG LCD. Later I will reverse engineer the LCD.

Step 1: Tools and Parts

Screwdrivers and pliers for disassembling the printer.

Oscilloscope or Logic Analyzer, a logic analyzer works best however an oscilloscope that saves readings can do the same job.

Multimeter for continuity testing and basic values.

You don’t need the whole printer but you will need the power supply, the main board, the control board, the LCD, cables, and the WiFi module.

Step 2: Disassemble the Printer

Take the printer apart and sort out the parts you will need, the main board, the control board, the LCD, cables, and the WiFi module.

I searched the net and couldn’t find a dattasheet on the K30345 WLAN WiFi module with pinouts. This module has 8 pins and many WiFi modules only needs four pins, + voltage, ground, data +, and data -.

I sorted out enough parts so that the LCD will display error codes.

Not every device will be the same so you may need more components than I did for this printer.

Step 3: Assemble the Parts

Assemble the parts you will be testing and turn on the printer.

When you turn the printer on, it should go into diagnostics mode.

Once it has completed diagnostics it should display error codes this is normal.

Step 4: Test the Main Board Ribbon Connector

Start by testing the WiFi ribbon connector on the main board using the multimeter.

Disconnect the WiFi module and measure the voltage of each pin from the ribbon connector to ground on the main board one at a time. Make a record of the outputs with the printer off.

Next measure the voltage of each pin from the ribbon connector to ground, one at a time turning the printer on and off as you wait for error codes. Make a record of the outputs with the power on.

Compare the pin outputs with the power off and the power on, since pin 7 is a steady 3.4 volts weather the printer is on or off it can be safe to assume pin 7 is VCC.

Step 5: Oscilloscope Test

Since pins 2, 5, and 6, on the main board ribbon connector never changed at 0 volts I suspected they were ground or no connection and I checked them with the oscilloscope power on or off there was no change.

Pin 7 was a steady 3.4 volts so I assumed it is safe to say pin 7 is VCC.

Pins 1, 3, and 4 at 1.5 volts could be a signal showing a lower than normal voltage on the multimeter, however when I checked them with the oscilloscope there was no signal.

Pin 8 starts at 0 volts increases to 3.4 volts when the power is turned on and then drops to 0 volts when the error codes come on the display. I suspect it was Enable or diagnose.

Step 6: Multimeter Test on the WiFi Module

Using the continuity settings of my multimeter, I checked the pins on the ribbon connector with the ground on the WiFi module one pin at a time and made note of the results.

Next I tested the test points on the WiFi module with the pins on the ribbon connector and made note of which test point is which pin.

I got a resistance on pins 1, 2, 5, 6, and 8 at the ribbon connector to ground, and 0 impedance or no resistance at pins 3, 4, and 7 from the ribbon connector to ground. This told me pins 3, 4, and 7 are ground.

Since pins 2, 5, and 6 on the main board ribbon connector were ground or no connection, and pins 3, 4, and 7 went to ground on the WiFi modules ribbon connector. I came to the conclusion the ribbon reverses between the two connectors so that pin 1 on the main board is pin 8 on the WiFi module.

Since pin 7 on the main boards ribbon connector is a steady 3.4 volts that would make pin 2 on the WiFi module VCC. Now we have 4 pins on the WiFi module figured out.

Pin 2 VCC

Pin 3 Gnd

Pin 4 Gnd

Pin 7 Gnd

Step 7: Oscilloscope Testing the Module

Reconnect the WiFi module and using an oscilloscope test the module at the test points.

Turn the printer on and record the responses one pin at a time as you turn the printer on and off, watch the error codes on the LCD.

This time I got a much different response from the 5 pins connected to the test points.

The test point connected to pin 2 on the module was a steady 3.3 volts confirming pin 2 is VCC.

The test point connected to pin 1 on the module went from 0 volts to 3.3 volts back to 0 volts then back to 3.3 volts and stayed there.

At the same time as the signal on pin one dropped from 3.3 to 0 volts and back up to 3.3 volts, the test point connected to pin 8 went from 0 volts to 3 volts and stayed there. Pin 8 only did this when the WiFi module was connected and pin 1 was at 3.3 volts. This made me suspect pin 1 was enable and pin 8 was ready.

The test point connected to pin 5 remained at 0 volts.

The test point connected to pin 6 had a repeating signal that flashed in sync with the error codes. This made me suspect the printer was trying to tell a computer it wasn’t ready to run and waiting for a response from a computer making pin 6 data into the module.

Since there was no computer was trying to communicate with the printer that should make pin 5 data out of the module.

Step 8: The Pinouts

The minimum number of pins on a WiFi module is 4; VCC, Gnd, D+, and D-. they can have extra VCC pins, or they can have extra Ground pins, Enable in, Ready out, Reset, and NC or No Connections.

The K30345 WLAN WiFi module has 8 pins, Enable, VCC, Gnd, Gnd, D-, D+, Gnd, and Ready .