04 · TTL Serial Port (Wireless Serial)
← Back to overview | Applies to: JUXI Technology KVM&HUB&TTL
What It Is
The 6-pin TTL port is a serial passthrough port: connect a dev board, sensor, etc. and its serial data is output from two places "simultaneously" (bidirectional):
┌─→ PC serial port (USB; recognized as "USB-BLE-SERIAL CH9143")
External device → 6-pin header ┤
└─→ Bluetooth wireless (phone BleUart app, see 03)Measured reference: with an IMU sensor connected, both the PC serial port and Bluetooth steadily received about 1650 bytes/second.
Pinout and Wiring
Left to right: GND RXD TXD TNOW 3V3 5V
| Pin | Description | Wiring |
|---|---|---|
| GND | Ground | Connect to the external device's GND (mandatory) |
| RXD | Local receive | Connect to the external device's TXD (crossed) |
| TXD | Local transmit | Connect to the external device's RXD (crossed) |
| TNOW | Transmit-direction indicator | Leave unconnected |
| 3V3 | 3.3 V power output | Can power low-power peripherals (choose either 5V) |
| 5V | 5 V power output | Can power low-power peripherals (choose either 3V3) |
Key points: TX/RX must be crossed; logic level is 3.3 V; the power pins are outputs — never feed power back into them; power low-power modules only.
(Illustration: tutorial asset 12 – TTL wiring example)
Using It on a Computer
- Connect this product to the computer via Type-C (either PC1 or PC2).
- The system recognizes the serial port
USB-BLE-SERIAL CH9143automatically (driver-free on Windows 10/11). - Open it with any serial tool; parameters: 115200, 8N1.
- Data from the external device streams in immediately (you can also send data to the device).
Connecting Dev Boards (Raspberry Pi / Jetson)
3.3 V logic level — direct connection works (crossed wiring, GND connected):
| This product | Raspberry Pi | Jetson (Orin series 40-pin) |
|---|---|---|
| RXD | Pin8 (GPIO14 / TXD) | Pin8 (UART1_TXD) |
| TXD | Pin10 (GPIO15 / RXD) | Pin10 (UART1_RXD) |
| GND | Any GND (e.g., Pin9) | Any GND (e.g., Pin9) |
On Raspberry Pi, enable the serial port in
raspi-config; on Jetson, enable the 40-pin UART first. Typical scenario: dev board serial → KVM → watch logs on the PC while your phone also views them via Bluetooth (wireless debugging).
(Illustration: tutorial asset 10 – Jetson pinout, 11 – Raspberry Pi pinout)
Troubleshooting: No Serial Data?
Check in order:
- Is the external device's TX/RX crossed and GND connected?
- Is the external device's baud rate 115200?
- Is the external device powered (you may use this product's 5V/3V3 pins)?
- Is the PC serial port occupied by another program? When the device switches to the other computer, the port briefly disappears (normal).