Control A Motor With A Touchpad

There are a surprising wealth of parts inside of old laptops that can be easily scavenged, but often these proprietary tidbits of electronics will need a substantial amount of work to make them useful again. Obviously things such as hard drives and memory can easily be used again, but it’s also possible to get things like screens or batteries to work with other devices with some effort. Now, there’s also a way to reuse the trackpad as well.

This build uses a PS/2 touchpad with a Synaptics chip in it, which integrates pretty smoothly with an Arduino after a few pins on the touchpad are soldered to. Most of the work is done on the touchpad’s built in chip, so once the Arduino receives the input from the touchpad it’s free to do virtually anything with it. In this case, [Kushagra] used it to operate a stepper motor in a few different implementations.

If you have this type of touchpad lying around, all of the code and schematics to make it useful again are available on the project page. An old laptop in the parts bin is sure to have a lot of uses even after you take the screen off, but don’t forget that your old beige PS/2 mouse from 1995 is sure to have some uses like this as well.

11 thoughts on “Control A Motor With A Touchpad

  1. With at least two buttons and two axes, and only needing 2 GPIOs, every average PS/2 touchpad is begging to be bodged onto something. The code complexity is the tradeoff, but you knew that :P
    I have been hoarding around 12 of them forever. I know what I want them to do (vaguely) but sometimes my brainbox is like an EZ Bake Oven fitted with a (60W-equivalent) LED bulb instead of the Right Thing™ –sometimes you really do need more heat than light and sometimes even half-baked would be an improvement.

  2. Is this again one of those cases where you can’t actually find a PS2 touchpad anywhere, because they’re all USB or some other not-microcontroller-friendly interfaces?

    1. I would guesstimate that they were dying off from around 2005 when chipsets began to drop PS/2 support. So your older athlon and P4-m machines will likely have PS/2 touchpads. This C2D machine I’m currently hammering on claims to have a PS/2 touchpad, at least the drivers say it does. It’s a socket P with 965 chipset, and I believe there was a lot of legacy stuff dropped after the 9xx series by Intel.

      1. The ASUS U46E from not as long ago (2nd Gen i5, DDR3) has a functionally limited, China-sourced PS/2 TP. I haven’t torn into many newer things but it seems to still be normal to have one or two externally available buses on the keyboard controller (often a chip by ENE with many duties and its own firmware) which also presents the keyboard to the system the same way, i8042 compatible.

      2. Chipsets might’ve dropped PS/2, but it was picked up by ECs (embedded controller ICs, same IC that is responsible for power management, fan control, processing buttons and scanning the internal keyboard, usually connected through LPC) and has been supported by them for ages – well, I guess, in the end, it’s just a matter of PS/2 firmware. Newer touchpads use I2C + an interrupt pin, as far as I know.

  3. “This build uses a PS/2 touchpad with a Synaptics chip in it, which integrates pretty smoothly with an Arduino after a few pins on the touchpad are soldered to.”

    It is improper grammar to have a dangling participle to end a sentence with.

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