Developing with a custom nRF93M1 board

This page covers moving from the nRF93M1 DK to your own hardware.

When you replace the DK with your custom board you must select the host processor, and you are responsible for the RF and power design. The module interface itself does not change.

Choosing a host

The module talks to the host over UART or USB, so the host does not have to be a Nordic device. The following are the options:

Host	Integration model	Notes
nRF54L15, as on the DK	AT commands or PPP over CMUX	Best supported path. Board files and samples exist.
Another Nordic SoC	AT commands or PPP over CMUX	Supported through the generic Zephyr cellular modem driver.
A third-party MCU	AT commands	No nRF Connect SDK dependency. Implement the AT interface on your own stack.
A Linux or Windows system	USB RNDIS or CDC-ECM	The OS owns the network stack. No driver development.

If you are building a small battery-powered device, the AT command model on a modest host is the most power-efficient and lowest-footprint combination. See Host and modem architecture.

Creating board files

Follow Defining custom board for the general process, then add the module.

For the AT command model, the module needs no devicetree node. Configure the UART your host uses, and drive the control signals as ordinary GPIOs.

For the PPP model, declare the module as a child of the host UART node using the nordic,nrf93m1 compatible. Start from the nRF93M1 DK board files rather than writing them from scratch. The modem node is declared in the nrf93m1dk_nrf54l15_common_0_3_0.dtsi file, and copying it preserves the control signal mapping and the CMUX settings that are known to work.

For the full property list, see PPP over CMUX. Only mdm-power-gpios is required, but a production design should also connect reset, DTR, and ring.

Two properties deserve a decision rather than a default:

autostarts

Set it only if your hardware brings the module up without a power or reset pulse. If it is set wrongly, the driver waits for a ready indication that never arrives.

cmux-close-pipe-on-power-save

Saves host power by closing the UART during power save, but then the module has to wake the host over RING. Do not enable it unless you wired mdm-ring-gpios.

Electrical design

Parameter	Requirement
Supply voltage	Single VBAT rail to both VDD pins, 3.3 V to 4.5 V, 3.8 V typical
GPIO logic level	1.8 V, driven from the module’s internal LDO. No external I/O supply required.
LDO_OUT	1.8 V nominal, up to 120 mA, available to the host
Operating temperature	-35 to +75 °C

The most common custom board issues are as follows:

Peak transmit current

The module draws several hundred milliamps during transmit bursts. Your supply must hold regulation through those bursts, and your decoupling must be sized for them. A supply that works at idle and browns out on transmit produces registration failures that look like RF problems.

Level shifting

Module GPIO logic is 1.8 V. If your host runs at 3.3 V, level shift every signal, including POWERKEY, nRESET, the UART lines, and the status pins.

Power sequencing

Follow the sequencing in the nRF93M1 Datasheet. Do not drive module pins while the module is unpowered.

RF and antenna design

Cat 1 bis uses a single receive antenna, so the module has one 50 ohm antenna pin, ANT. There is no diversity or MIMO routing to lay out, which is a meaningful simplification compared with full Cat 1.

• Design the antenna feed as a 50 ohm controlled-impedance trace, kept as short as practical.

• Include a matching network footprint, even if your antenna does not require tuning.

• Follow the reference layout and keep-out guidance in the nRF93M1 Datasheet and the DK design files.

• Validate the antenna with AT%RFTEST, which measures RSSI without a network connection. See RF testing.

Important

Antenna performance dominates real-world connectivity. A design that registers on a bench next to a base station might fail at the cell edge. Test at the edge of coverage, not only in good conditions.

Designing for both variants

The two variants in Module variants are pin, size, and software compatible. Each variant requires its own board design and modem firmware image. You select the variant by which part you place.

Design for this deliberately:

• Develop and qualify on nRF93M1-LABA, then place nRF93M1-LACA for markets that need the wider band set, with no PCB change.

• Keep the RF design suitable for the full frequency range, 617 MHz to 2.69 GHz, even if you ship the multi-regional variant first. The global variant uses bands the regional variant does not, and an antenna tuned only for the regional band set will underperform on them.

Note

Regulatory approval applies to your product, not just to the module. Module pre-certification reduces your certification effort but does not remove it. Confirm the scope of the module certifications for your target markets and variant early, because this affects schedule more than it affects design.

Design review checklist

The following is the design review checklist to be considered:

• Supply holds regulation through peak transmit current.

• All host-to-module signals are level shifted to 1.8 V if required.

• Power sequencing matches the datasheet.

• POWERKEY and nRESET are both host controllable.

• UART1_DTR is connected. It is the only baud-rate-independent wake path.

• UART1_RI is connected if the host will sleep and needs the module to wake it.

• Host CTS has a pull-up, required when using hardware flow control.

• RFC1 through RFC3 are left for RF tuner control, not repurposed as GPIO.

• UART hardware flow control lines are connected.

• Antenna feed is 50 Ω with a matching network footprint.

• Current measurement points are available for bring-up.

• A serial path exists for modem firmware recovery. See Updating over serial.

• SIM interface matches your SIM class, 1.8 V Class B or 3 V Class C.