JetKVM is an open-source KVM over IP (Keyboard, Video, Mouse) solution designed for efficient remote management of computers, servers, and workstations. Originally launched as a Kickstarter project, I supported it and received my own device in early 2025. Like many renowned reviewers, I was impressed by the build quality of both the hardware and the software. However, this post is not just another review of the device. Instead, it will describe how you can further extend its functionality to manage even more devices—specifically, how to control your serial devices over a network.
The team behind the device included an extension port in the form of an RJ-11 connector (6p6c), which provides a 3.3V logic serial connection.
In the latest update (0.3.8), released last week, the team resolved several issues with the terminal in Firefox. With these fixes in place, I believe now is the perfect time to demonstrate how to control your serial devices over the network, as the device’s terminal functionality is now working flawlessly.
Requirements
- The main requirement is a 6P6C connector (RJ11, RJ14, RJ25) to utilize the extension port. If you don’t have a punch-down tool for the specific connector, the simplest solution is to use an extension cable, as I did.
The extension cable I used was a flat cable that adhered to the old Bell System’s solid color code.
Using these specific colors, the following table shows the correspondence between the extension port and cable colors (unused cables are crossed out):
| Extension Port Pinout | Connector Color |
|---|---|
| GND | White |
| UART_RX | Black |
| UART_TX | Red |
| 3V3 | Green |
| N/C | |
| VSYS (5V Bus) |
- A 5V to 3V biderctional logic converter. For controlling RS232 devices:
- A MAX3232 logic converter. For controlling 5V logic devices: .
Loading the Serial Extension
To enable the "Over the Network" terminal, open a browser window and navigate to your JetKVM device’s IP address. From the top menu, select Extension, then click the Load button next to the Serial Console Extension. The page will reload, and connection settings will appear. These settings depend on the specific device you are connecting to—fill them in accordingly. Once done, click the >_ Open Console button. You’re now ready to control your serial device over the network.
Controlling Raspberry PI, ESP32 or any 3.3V Serial Logic Device
Any device using 3.3V logic is fully compatible with JetKVM. Simply cross-connect the Tx and Rx cables between your device and the extension port, then connect their GNDs. Once that’s done, you’re ready to go!
Raspberry PI
For Raspberry PI enable the Serial communication by editing /boot/firmware/config.txt (or /boot/config.txt if you are using an older version of Raspberry Pi OS) and append:
enable_uart=1Then, with your Raspberry PI off, plug the Tx, Rx and Ground Pin to Extension Port’s Rx, Tx and Gnd Pins.
Pinout
| JetKVM Pin Number | Extension Cable Color | Raspberry PI Pin No |
|---|---|---|
| 1 | White | 6 (or any other GND) |
| 2 | Black | 8 (GPIO 14) |
| 3 | Red | 10 (GPIO 15) |
Arduino or any other 5V Serial Logic Device
For devices using 5V Serial a Logic Level Converter is required. In the current implemetation I used a two channel 5v to 3v biderctional logic converter Aliexpress Link
The logic level converter is divided into two parts: the Low Voltage (or level) Side (LV Side) and the High Voltage (or level) Side (HV Side). JetKVM should be connected to the Low Voltage Side and provide 3.3V to the LV pin, while the Arduino (or any other 5V logic device) should be connected to the High Voltage Side and supply voltage to the HV pin.
One of the two devices must have its cables crossed for communication. I chose the Arduino, but it doesn’t really matter—just pick one of the two devices and cross the cables.
Pinout
| JetKVM Pin Number | Extension Cable Color | Converter Pin | Arduino Pin No |
|---|---|---|---|
| 1 | White | Gnd | |
| 2 | Black | RX0 (LV Side) | |
| 3 | Red | TX1 (LV Side) | |
| 4 | Green | LV | |
| Gnd | Gnd | ||
| HV | 5V | ||
| TX0 (HV Side) | 0 (RX) | ||
| RX1 (HV Side) | 1 (TX) |
Network Equipment (CISCO, Fortinet, etc) and other RS-323 devices
Yes, with JetKVM, you can manage your CISCO, Fortinet, or any other RS232-enabled equipment by setting up an Out-of-Band (OOB) network using your JetKVM device. To enable communication, I used a MAX3232 logic converter (Aliexpress Link)—note that it is not recommended for use at baud rates higher than 115200. Using the official CISCO console cable pinout for Catalyst 2960 routers, I created a custom version of a console cable. Instead of a DB9 connector, this cable uses only the TX, RX, and GND pins, connecting directly to the MAX3232 Logic Level Converter.
Pinout
| JetKVM Pin Number | Extension Cable Color | Converter Pin | Ethernet Cable Pin/Color (EIA/TIA T568B) |
|---|---|---|---|
| 1 | White | – (TTL Side) | |
| 2 | Black | → (TTL Side) | |
| 3 | Red | ← (TTL Side) | |
| 4 | Green | + (TTL Side) | |
| – | 4 – Blue | ||
| ← (RS232 Side) | 6 – Green | ||
| → (RS232 Side) | 1 – Green/White |
Sum up
The team behind JetKVM has done incredible work, making everything available, including:
- A 3d Model of the device.
- Firmware and detailed instructions for developers.
- The option to self-host your own cloud provider, enabling internet access without your data passing through the company’s servers.
It’s great to see such transparency and flexibility in a project.