Overview

Introducing TerraLink EC200U, a cellular modem board that gives Glyph development boards and other microcontrollers a connection to the mobile network. Glyph runs your application and collects sensor readings; the EC200U handles cellular registration and data communication. This is useful for remote monitoring, telemetry, and connected devices that need to operate beyond a local Wi-Fi network.

• Modem: Quectel EC200U series.
• Cellular Data: LTE with rated peak speeds of 10 Mbps download and 5 Mbps upload.
• Dimensions: 63.50 × 45.72 mm PCB, with 1.6 mm nominal thickness.
• Host Connections: USB 2.0 and a five-pin UART/control header at 2.54 mm pitch.
• Logic Levels: 3.3 V on the external UART header, translated to the modem’s internal 1.8 V interface.
• SIM: One nano SIM holder.
• Power: USB-C input and a separate VIN/GND terminal, with onboard regulation for the modem.
• Additional Features: Local power-key and reset buttons, activity indicators, antenna connectors, and signal test points.

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What the EC200U Does

The modem manages the cellular radio connection so the host controller does not have to implement it. The host sends AT commands: short text instructions that configure the modem, check its status, and request communication operations. The modem returns responses and can also send notifications when its state changes. The EC200U series includes network functions such as TCP/UDP, MQTT, and HTTP/HTTPS. MQTT is commonly used for exchanging small messages with an IoT service, while HTTP/HTTPS lets an application communicate with a web API. The commands available depend on the installed firmware. See the Quectel EC200U specifications. The published LTE rates are modem peak ratings. Actual application speed depends on signal strength, the operator, the data plan, the server, and the connection between Glyph and TerraLink. A UART connection can limit throughput even when the cellular connection is faster.

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Connectivity

Use the cellular antenna connection and an activated, compatible SIM for mobile-network operation. The board also routes separate BLE and GNSS antenna connections; availability of those functions depends on the exact EC200U variant and firmware. Cellular band support also varies by variant, so check the module against the network you intend to use. USB-C provides access from a computer for modem communication and supported firmware tools. The UART header provides the connection to Glyph and other 3.3 V controllers. The header also exposes power-key and reset controls for applications that need to manage the modem’s operating state.

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Using TerraLink with Glyph

Glyph compatibility comes through the UART interface. Your program runs on Glyph, sends commands to TerraLink, reads the responses, and decides what to do next. For example, Glyph can read a sensor, send the value to a cloud service, and retry if the network is temporarily unavailable. The onboard level translator connects the 3.3 V host interface to the modem’s 1.8 V UART. Other controllers can use the same connection when their UART voltage is compatible. A 5 V host requires suitable level shifting, and all connected boards need a common ground. Start with Programming with Glyph for a wiring table and an Arduino serial-console example. See Pinouts for connector functions.

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Development Options

For standard AT firmware, develop the host application in an environment supported by your Glyph board, such as Arduino, ESP-IDF, or MicroPython. You can also control the modem directly from a computer over USB before moving the command sequence into your application. EC200U additionally has vendor development options for running application logic inside a supported modem variant. QuecPython requires matching QuecPython firmware, while QuecOpen is a separate vendor development route. These options require checking the exact variant and firmware package; uploading a Glyph sketch does not replace the modem firmware. See Quectel’s firmware guide.

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Power Supply

Power TerraLink through its supported power input rather than a controller GPIO. Cellular transmission draws bursts of current; an inadequate supply can cause resets or lost connections. The VIN screw terminal is marked for 5–15 V DC; USB-C uses 5 V. Choose a supply that can handle cellular current bursts.