The THR-Footswitch has been developed especially for the guitar amplifier THR10 by YAMAHA. It extends the ability to store pre-tuned amplifier settings from 5 to 100 and allows you to switch with your foot while playing.

The THR editor supplied by YAMAHA allows separate tuning via PC or Mac. The THR-Footswitch simulates a PC with this software and transfers the required data like a PC via USB. First, the settings must be made on the PC. Settings that have been found to be good can then be saved. The data is stored in a YDL file. This file must be copied to an SD card and can then be read by the THR-Footswitch. The file must have the name THR10.YDL. To change the amplifier settings, press the right (up) or left (down) footswitch.

YAMAHA now builds quite a number of different THR models. I built this footswitch for the THR10 and it works. I don't know if it's compatible with the other variants, but I assume it is. Only the matching THR editor software would have to be used.

Main component is an Arduino UNO. In addition some further components are necessary:
A USB Host Shield to connect the Arduino to the amplifier.
A MicroSD card reader for the SD card with the stored presets.
An OLED display. It shows the current status, number and name of the selected preset.
Two footswitches to change sets

The Arduino and all components are powered by a 9V block battery. I use a NiMH battery with 8,4V.

There is no on/off switch. The THR footswitch is turned on with the right footswitch. This has a second contact that supplies power to the Arduino. After booting the Arduino, the optocoupler switches the MOSFET through and supplies itself with power. If no key is pressed for a certain time, the Arduiono switches itself off. The setting in the amplifier remains the same. By pressing both buttons at the same time the THR-Footswitch can be switched off.

1. setup: Definition of pins and variables, initialization of components. OLED display, USB host, SD card reader
2. main routine: It consists of only three lines. Checking whether a button has been pressed, scrolling the text display further and monitoring the time for the automatic switch-off. Everything else is done in the subroutines.
3. subroutines (SR): All tasks of the program are divided into subroutines.
button check
scroll
send_patch
displayNumber
read_name
switch_off

Yes, the driver libraries for USB host, card reader and display are required. SPI.h SD.h Usb.h usbh_midi.h SSD1306Ascii.h SSD1306AsciiAvrI2c.h You can download them from https://github.com/arduino/Arduino .

There is an additional font file. I made it myself because I wanted bigger numbers. The file is called Cooper50.h and must be in the folder fonds.

No. Since it's a prototype, I used a universal circuit board. The wiring can be seen in the wiring diagram and the photos.

The case is also not for sale. It's one of the first 3D prints I made.

No. This is just a suggestion. I do not take over any guarantee for any errors. I also do not know whether the components currently available still work together in this way.

No. The construction of the THR Footswitch was a unique project. My website is only meant to show the development and possibly encourage you to build your own model. I have discovered a company on the Internet at https://patchbox68.com/ that offers similar products for sale (I don't know if they know my site...). But apparently the company doesn't exist anymore (2020). Now and then devices are still offered on the Internet.