Three interfaces cover almost every touch project: USB, I2C and RS232. The choice affects your firmware, your cable length and, occasionally, whether the product works at all.
USB HID — the default
USB is a HID device: the operating system sees a mouse-like digitizer and no driver is needed on Windows, Linux, Android or Chrome OS. Cable length up to 3 m without a hub, 5 m with a powered hub, and 80–100 m over a USB extender. If you have no reason to choose otherwise, choose USB.
I2C — for embedded boards
I2C is what you use when the touch panel talks directly to a single-board computer or a microcontroller with no USB host. It is a 4-wire bus (VCC, GND, SDA, SCL) plus an interrupt line, and the cable must be short — under 300 mm in practice, because I2C is not designed for distance. It also means you own the driver: on Linux you need the right kernel module, and on a bare MCU you write the polling loop.
RS232 — for the retrofits
RS232 still appears in industrial control cabinets, medical consoles and anything designed before 2005 that is still in production. It survives 15 m of cable in a noisy cabinet and it does not care about ground loops. If you are replacing a touch panel in an existing machine, RS232 is often the only option that does not require changing the host software.
What we set before shipping
Interface, baud rate, VID/PID, report protocol and the coordinate origin. If you are replacing a part from another supplier in an existing product, send us the old controller's settings and we will match them so the host software sees no change.
Long cable runs
If the controller is more than 3 m from the host, use USB with an active extender rather than a longer passive cable. Above 10 m, either move the host closer or use RS232. A marginal USB cable produces exactly the failure mode customers describe as "the touch stops working when the machine warms up".
Tell us the size. We will tell you what fits.
Send a drawing, a size, or just a photo of the screen you are building around. Our engineers reply with a matched part and a price within 12 working hours.