KSP-N51U Quick Start
The KSP-N51U is an internal LTE-M / NB-IoT module in the KORLINX industrial LTE-M product series. This guide helps you prepare the module hardware, connect the U.FL antenna, connect the UART host interface, power the module correctly, and verify basic AT command communication.
Unlike the KSE-91A external modem, KSP-N51U is a PCB-level internal module. This Quick Start focuses on hardware preparation, UART host connection, antenna connection, USIM preparation, and basic communication verification.
Quick Start Flow
Use the following flow for first-time bring-up.
| Step | Action | Expected Result |
|---|---|---|
| 1 | Review the hardware overview and pin list | You can identify the antenna connector, power pins, GND pins, and UART pins |
| 2 | Connect the LTE antenna | Antenna is securely connected to the U.FL connector |
| 3 | Prepare the Nano USIM | SIM is ready for cellular network access |
| 4 | Connect UART and GND | Host can communicate with the module through UART |
| 5 | Apply 3.3–5 V DC power | Module powers on from a stable supply |
| 6 | Open the host UART port | Serial terminal or host firmware is ready |
| 7 | Send AT | Module returns OK if communication is working |
| 8 | Continue network and GNSS checks | Module is ready for LTE-M / NB-IoT testing |
For the first bring-up, verify the UART path first. A simple AT → OK response confirms that power, GND, and UART wiring are working.
Hardware Overview
The KSP-N51U hardware provides a compact internal LTE-M / NB-IoT module form factor with a U.FL antenna connector and a 2.54 mm header pin type host connection.
Module Overview
| Part | Description |
|---|---|
| Module type | Internal LTE-M / NB-IoT module |
| Host connection | 2.54 mm header pin type |
| Antenna connector | U.FL |
| Control interface | AT-COMMAND over UART |
Antenna Connector
The KSP-N51U uses a U.FL antenna connector. Connect the LTE antenna before starting cellular network tests. If your application uses GNSS, make sure the antenna design and placement support the required GNSS performance.
For better signal quality, keep the antenna away from large metal objects and place it where cellular reception is available.
Host Connection
The module connects to the host system through a 2.54 header pin type connection. Use the hardware reference or board design file for the exact pin assignment before wiring.
Do not assume the pin order from the product photo alone. Always verify the pinout from the official hardware reference or board design before applying power.
Pin List
The KSP-N51U uses two 14-pin header groups for power, UART, I2C, control, and GPIO-related signals.
Essential Pins for Quick Start
Use these pins for a basic power and UART communication test.
| Purpose | KSP-N51U Pin | Signal | Connect To |
|---|---|---|---|
| Power input | J1-1 or J1-2 | 3.3–5V | Stable 3.3–5 V DC supply |
| Ground | J1-3 or J1-4 | GND | Host / power supply GND |
| UART transmit | J2-1 | UART_TX | Host UART RX |
| UART receive | J2-2 | UART_RX | Host UART TX |
| Power control | J2-5 | PWR_ON | Host control signal, if used |
| Reset | J2-7 | nReset | Host reset control, if used |
Confirm the J1/J2 orientation on the actual PCB or carrier board before wiring 3.3–5V and GND. Incorrect power wiring may damage the module.
Specification
General
| Item | Specification |
|---|---|
| Model name | KSP-N51U |
| Product type | Internal type industrial LTE-M module |
| Cellular network | LTE-M / NB-IoT |
| MCU | 64 MHz Arm Cortex-M33 |
| Memory | 1 MB flash + 256 KB RAM, EXT 4 MB flash |
| Modem | Multimode LTE-M / NB-IoT modem |
| Data rate | Up to 375 kbps (LTE-M Cat-M1) |
| Tx power | Up to +23 dBm (LTE-M mode) |
| Frequency | 700–2200 MHz LTE band support |
| Protocol | MQTT, CoAP, HTTP, LwM2M |
| Control | AT-COMMAND (UART) |
| SDK | ESP32, STM32 Series, nRF52 Series |
| GNSS | Supported |
| USIM | Nano USIM, Supported Global and KT |
| Security | Arm TrustZone + Arm CryptoCell 310 |
| Interface | UART |
| Input voltage | 3.3–5 V DC |
| Antenna | U.FL |
| Connection | 2.54 header pin type |
| Size | 21 × 34 × 1.0 mm (PCB only, U.FL) |
Current Consumption
| Mode | Specification |
|---|---|
| Current consumption (Tx) | ~120 mA average in LTE-M mode, varies by band and output level |
| Current consumption (LP) | Under 5 µA in PSM / DRX power-saving mode |
Before You Start
Prepare the following items before wiring the module.
| Item | Description |
|---|---|
| KSP-N51U module | Main LTE-M / NB-IoT internal module |
| Host board or MCU | Host system with UART support |
| Stable DC power source | 3.3–5 V DC input according to the module specification |
| LTE antenna | Antenna connected through U.FL |
| Nano USIM | Active SIM profile for cellular network access |
| Serial terminal | PC tool or host software used to send AT commands |
Before powering on, confirm the supply voltage, common GND, UART wiring, and antenna connection. Incorrect power wiring may damage the module.
Connect the Hardware
1. Connect the Antenna
Connect the LTE antenna to the U.FL antenna connector before running network tests.
For better signal quality, keep the antenna away from large metal objects and place it where cellular reception is available.
2. Prepare the Nano USIM
Install or connect the Nano USIM according to your host board or product design.
| Check Item | Recommended Action |
|---|---|
| SIM format | Use Nano USIM |
| SIM service | Confirm that the SIM plan supports the target cellular network |
| SIM contact | Make sure the SIM is seated correctly in the host design |
3. Connect the UART Host Interface
KSP-N51U is controlled by AT-COMMAND (UART). Connect the module UART interface to the host UART interface.
| KSP-N51U Pin | Signal | Connect To |
|---|---|---|
| J2-1 | UART_TX | Host UART RX |
| J2-2 | UART_RX | Host UART TX |
| J1-3 or J1-4 | GND | Host GND |
The exact physical pin location depends on your carrier board or product design. Use the official pinout before wiring.
4. Apply Power
Apply stable 3.3–5 V DC power to the module.
| KSP-N51U Pin | Signal | Connect To |
|---|---|---|
| J1-1 or J1-2 | 3.3–5V | Power supply output |
| J1-3 or J1-4 | GND | Power supply ground |
After power is applied, open the host UART port from your PC tool or host firmware.
Verify AT Command Communication
After wiring and powering the module, verify that the UART communication path is working.
Basic Communication Check
Send a basic AT command from your serial terminal or host application:
AT
A normal AT command interface should return an OK response when the host UART communication is working.
If there is no response, check power, common GND, UART TX/RX direction, and the serial port settings used by your host firmware or test tool.
🎉 You're Ready!
Welcome to KORLINX Cellular Module
You've completed the basic hardware connection and UART communication check.
From power wiring to your first AT command response — that's an important first step.
- ✅ Connected the LTE antenna
- ✅ Prepared the Nano USIM
- ✅ Connected power and ground correctly
- ✅ Wired the UART host interface
- ✅ Sent your first
ATcommand - ✅ Received an
OKresponse from the module
What's next?
Network Attach
Continue with LTE-M / NB-IoT network registration and signal checks.
GNSS Preparation
Prepare antenna placement and test location-related features.
Network Attach
Use AT commands to configure the modem and check cellular status.
Host Integration
Integrate the module with your MCU, host board, or application firmware.
Your module is now responding over UART. You can continue with network connection checks and product integration.
Troubleshooting
| Symptom | Possible Cause | Recommended Action |
|---|---|---|
| No AT response | Power, UART wiring, GND, or serial setting issue | Check power input, common GND, TX/RX direction, and serial configuration |
| Module does not power on | Incorrect supply voltage or unstable power | Confirm 3.3–5 V DC input and power source capacity |
| Cannot attach to network | SIM, antenna, coverage, or network profile issue | Check Nano USIM, LTE antenna, cellular coverage, and AT command configuration |
| Weak signal | Poor antenna placement or low coverage | Reposition the antenna or test in a better coverage area |
| GNSS does not get a fix | Antenna placement or sky visibility issue | Improve antenna placement and allow more time for first fix |
| Unstable communication | UART wiring or host timing issue | Check UART wiring, ground connection, and host firmware handling |