Rotary Encoder with NeoPixels and USB Interface
The USB Knob is a versatile device that combines the functionality of a rotary encoder with the convenience of a USB interface. It is based on either the CH552E or CH554E microcontroller and is equipped with addressable LEDs, commonly known as NeoPixels. The unique combination of these components makes the USB Knob an ideal choice for a wide range of applications, including volume control for PCs.
One of the standout features of the USB Knob is that it requires no driver installation, making it incredibly easy to use. The device acts as a USB human interface device (HID), meaning that it can be recognized and utilized by most computers without the need for additional software.
The CH552E is a low-cost, enhanced E8051 core microcontroller compatible with the MCS51 instruction set. It has an integrated USB 2.0 controller with full-speed data transfer (12 Mbit/s) and supports up to 64 byte data packets with integrated FIFO and direct memory access (DMA). The CH552E has a factory built-in bootloader so firmware can be uploaded directly via USB without the need for an additional programming device.
This firmware enables the USB Knob to control the volume of your computer. By turning the knob, you can increase or decrease the volume, while pressing the knob will mute or unmute the sound. The device is recognized as a USB HID consumer multimedia keyboard and should work immediately without the need for any driver installation.
This firmware is designed to transform the USB Knob into a mouse wheel. By rotating the knob, it emulates the movement of a mouse wheel, allowing users to scroll up and down web pages, among other things. Pressing the knob is equivalent to clicking on the mouse wheel or the middle mouse button. The device registers as a USB HID mouse on the computer and should work immediately without the need for driver installation.
This firmware is perfect for customizing it according to your own preferences. It allows for the free mapping of USB HID actions to USB Knob events. The firmware is structured and commented in such a way that it should be possible to make adjustments even with basic programming skills. It is designed as a USB HID composite device that combines a keyboard, a mouse, and a game controller.
On Linux you do not need to install a driver. However, by default Linux will not expose enough permission to upload your code with the USB bootloader. In order to fix this, open a terminal and run the following commands:
echo 'SUBSYSTEM=="usb", ATTR{idVendor}=="4348", ATTR{idProduct}=="55e0", MODE="666"' | sudo tee /etc/udev/rules.d/99-ch55x.rules
sudo service udev restart
For Windows, you need the CH372 driver (recommended). Alternatively, you can also use the Zadig Tool to install the correct driver. Here, click "Options" and "List All Devices" to select the USB module, and then install the libusb-win32 driver. To do this, the board must be connected and the CH55x must be in bootloader mode.
A brand new chip starts automatically in bootloader mode as soon as it is connected to the PC via USB. Once firmware has been uploaded, the bootloader must be started manually for new uploads. To do this, the board must first be disconnected from the USB port and all voltage sources. Now press the BOOT button and keep it pressed while reconnecting the board to the USB port of your PC. The chip now starts again in bootloader mode, the BOOT button can be released and new firmware can be uploaded within the next couple of seconds.
Once the USB Knob firmware is installed, the bootloader can also be entered by holding down the rotary encoder switch while connecting the device to the USB port. In this way, the case does not have to be opened when new firmware is to be installed. The NeoPixels will then light up white as long as the device is in bootloader mode (approx. 10 seconds).
Install the SDCC Compiler. In order for the programming tool to work, Python3 must be installed on your system. To do this, follow these instructions. In addition pyusb must be installed. On Linux (Debian-based), all of this can be done with the following commands:
sudo apt install build-essential sdcc python3 python3-pip
sudo pip install pyusb
make flash
to compile and upload the firmware.python3 ./tools/chprog.py firmware.bin
.Install the Arduino IDE if you haven't already. Install the CH55xduino package by following the instructions on the website.
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