Pinouts

CLICK HERE TO DOWNLOAD HD TerraLink EC200U connects to a controller through its five-pin, 2.54 mm header. USB-C provides a separate connection for computer access and power. Use the pin-1 marker on the board to identify the header orientation; the numbers below follow the physical header pins.

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Communication Pins

The UART header uses 3.3 V logic. The onboard translator connects it to the modem’s 1.8 V interface.

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Power Connections

• USB-C: Accepts USB 5 V and carries modem USB data when a data-capable cable is used.
• VIN terminal, pin 1: External 5–15 V DC supply input, as marked 5V-15V on the board silkscreen.
• GND terminal, pin 2: External supply ground.

The 5–15 V range applies to the VIN screw terminal. USB-C accepts USB 5 V; do not apply 15 V to USB-C, the UART header, or any test pad. Observe the terminal polarity. The supply must handle cellular transmit-current bursts. A controller GPIO is a signal connection and cannot power TerraLink.

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SIM and Antenna Connections

The board has one nano SIM holder connected to the modem. Insert or remove the SIM with board power off. The SIM interface carries its own supply, clock, reset, and data signals; it is not an external controller expansion port. Check the installed module variant and firmware for BLE and GNSS support. Antenna connectors alone do not enable optional features. Use an antenna suitable for the intended radio and frequency bands.

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Buttons and Indicators

• Power key: Operates the modem’s local power-key input. Use the timing specified in the modem hardware guide.
• Reset: Operates the modem’s reset input.
• Power and activity LEDs: Provide local indication of supply and modem/UART activity. Confirm registration and connection state through modem responses.

The reset and power-key header connections use onboard driver circuits. They are not a supply switch, and their header control behavior differs from connecting directly to the modem’s active-low pins. Leave them disconnected for the basic UART example and use the local buttons.

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Solder Pads and Test Points

These small exposed pads provide access for measurement, diagnostic equipment, or soldered wires. They are separate from the main controller header. Disconnect power before soldering, use short insulated wires with strain relief, and keep solder away from neighboring pads.

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Supply and Ground Test Pads

5V

The USB 5 V rail. Measure against GND to check USB input power. This is separate from the 5–15 V VIN terminal.

3V8

The nominal 3.8 V modem supply. Measure against GND; an oscilloscope can reveal supply dips during cellular transmission.

3V3

The onboard nominal 3.3 V regulator output. Measure against GND to check this rail.

1V8

The modem-derived nominal 1.8 V rail. Measure against GND while the module is on. This measurement pad is separate from the BOOT pad group.

GND

One of the two ground test pads. Use it as the reference for voltage measurements or diagnostic equipment.

GND — Additional Ground Pad

The second ground test pad. Both ground pads connect to the same board ground. The voltage labels identify existing supply rails, not additional general-purpose power inputs. Power the board through USB-C or the VIN terminal. Do not inject voltage into these rails or assume they can power a Glyph board or other load; available output current has not been established.

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Log UART Pads: L_TX and L_RX

The EC200U log UART passes through the onboard 1.8 V-to-3.3 V translator. Use a 3.3 V TTL USB-to-UART adapter: adapter RX → L_TX, adapter TX → L_RX, and adapter GND → GND. Leave the adapter power lead disconnected.

L_TX — Log Output

The modem sends diagnostic data on this pad. Connect it to the compatible adapter’s RX input.

L_RX — Log Input

This pad receives diagnostic input from a compatible adapter’s TX output when required by the vendor procedure. Power TerraLink through its normal input, then capture the log using the baud rate and serial settings specified for the installed firmware. Log output is intended for diagnostics; availability and format depend on firmware. Use the main UART header for the documented AT-command examples.

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USB Data Pads: D+ and D−

D+ and D- carry USB data, not UART or GPIO signals. Prefer the USB-C connector for normal computer access and firmware updates. An alternate USB connection also needs the correct ground, VBUS/power arrangement, and USB wiring. Keep the data pair short and routed together; do not attach two USB hosts simultaneously or leave long wire branches on the USB signals.

D+ — USB Data Positive

The USB positive data signal connects to the modem’s USB_DP pin and the USB-C data connection.

D− — USB Data Negative

The USB negative data signal connects to the modem’s USB_DM pin and the USB-C data connection. Use D+ and D− together as a USB differential pair.

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Boot-Mode Pads: 1V8, BOOT, and GND

These are three separate solder pads for accessing the modem’s USB boot-mode input. They are used for firmware download or recovery, not for normal AT-command control or programming a Glyph board. The separate 1V8 test point elsewhere on the board is connected to the same 1.8 V rail. The pad names describe electrical connections; the correct recovery connection differs between EC200U and A7672S.

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EC200U: BOOT High for USB Download

EC200U’s USB_BOOT input is active high. For forced USB download, temporarily connect BOOT to 1V8 before powering on the module, following Quectel’s startup sequence. Connect USB-C to the computer and use the matching Quectel drivers, download tool, and firmware image. The modem enters its download interface rather than starting its normal application. For normal operation, leave the separate pads unconnected and do not hold BOOT high during startup. After recovery, remove the temporary BOOT-to-1V8 connection before the next normal startup. See the Quectel EC200U hardware guide, USB_BOOT interface section. Continue with Programming with Glyph for the wiring table and first communication test.