The **EVK-R4** (Evaluation Kit for the SARA-R4 series) is a comprehensive development platform designed by u-blox to test and integrate LTE-M, NB-IoT, and EGPRS cellular modules. It provides the necessary hardware interfaces to bridge a PC or microcontroller with the SARA-R4 cellular module. ### Core Electronic Components The board is divided into several functional blocks that facilitate power management, communication, and signal monitoring. | Component Category | Description | Key Parts/Features | | :--- | :--- | :--- | | **Cellular Module** | The "brain" of the kit. | u-blox **SARA-R4** series (e.g., R410M, R412M). | | **Power Supply** | Converts input voltage to module levels. | 5V via USB or 9-12V DC Jack; integrated step-down converters. | | **USB Interfaces** | Provides connectivity for AT commands and trace. | Two Mini-USB ports (Native and Debug/UART). | | **SIM Interface** | Connects the module to the carrier network. | Standard SIM card slot (1.8V/3V support). | | **Antenna Connectors**| RF signal input/output. | SMA connectors for Cellular and GNSS antennas. | --- ### Detailed Hardware Architecture #### 1. Power Management The EVK-R4 is designed to handle the specific current peaks of cellular transmission. * **Voltage Regulation:** High-efficiency switching regulators provide a stable 3.8V supply to the SARA-R4 module. * **Current Measurement:** The board includes a 0.1 $\Omega$ shunt resistor and specific headers (J103) to measure the module's power consumption using an oscilloscope or digital multimeter. #### 2. Communication Interfaces The kit bridges the module's hardware pins to accessible ports: * **UART:** The primary communication interface. It is routed through an **FTDI USB-to-UART bridge**, allowing developers to send AT commands directly from a PC. * **DDC (I2C):** Used for communicating with external u-blox GNSS modules. * **GPIOs:** Important pins like `Power_On`, `Reset`, and `V_INT` are mapped to LEDs and manual push-buttons. #### 3. Signal Indicators (LEDs) The board utilizes several LEDs to provide visual feedback on the system status: * **DS100 (Blue):** Indicates the module is powered on. * **DS102 (Green):** Indicates cellular network status (blinking patterns represent different states). * **DS105 (Red):** Indicates the 3.8V main power supply is active. --- ### Technical Specifications Summary | Feature | Specification | | :--- | :--- | | **Input Voltage** | 5.0 V (USB) or 9.0 - 12.0 V (DC Jack) | | **Module Logic Level** | 1.8 V | | **RF Connector** | SMA (Female) | | **Data Rate** | Up to 375 kb/s (LTE-M) / 125 kb/s (NB-IoT) | --- ### Connector Pinout (Expansion Header) The EVK-R4 features a 14-pin connector to interface with external hardware or sensors: ```markdown Pin 1: VCC_TARGET (1.8V) Pin 2: GND Pin 3: UART_TXD Pin 4: UART_RXD Pin 5: UART_RTS Pin 6: UART_CTS ... and other GPIOs/I2C pins. ```