ModalAI M0184 Gemini 915MHz ELRS

ModalAI's M0184 Gemini 915MHz ELRS

Table of contents

1. Summary
   1. Transmitter Compatibility
   2. VOXL SDK Support
   3. Dimensions
      1. 3D Drawings
   4. Features
2. Hardware
   1. Hardware Block Diagram
   2. Connectors
      1. Summary
      2. J4 - Header Solder Pads
      3. J1 - ANT1
      4. J2 - ANT2
      5. S1 - Bind button
      6. D1 - Green LED
      7. D2 - Red LED
   3. Programming Test Points
3. User Guides
   1. VOXL SDK
   2. VOXL 2 Wiring Guide (M0054)
4. List of Certifications

Summary

Transmitter Compatibility

In general, follow Express LRS guidance selecting 900MHz compatible transmitters.

The M0184 runs ELRS 3.x receiver firmware by default, bundled with voxl-elrs. voxl-elrs also bundles ELRS 4.x firmware for the M0184, which is experimental. A transmitter must meet all of the following to bind:

• The same major ELRS version as the receiver. With the default 3.x receiver firmware, the transmitter module must run ELRS v3. Downgrade a 4.x transmitter to the latest ELRS 3.x release using the standard ExpressLRS transmitter update process, or move the receiver to 4.x as described below.
• A 900 MHz or dual-band module, operating in the low band.
• Not a 2.4 GHz-only module. The built-in ELRS module in many handsets, including the RadioMaster TX16S and Boxer, is 2.4 GHz only and cannot bind to the M0184. Use a 900 MHz or dual-band external module in the radio’s module bay instead.

ELRS 4.x on the M0184 is experimental. To try it, update the transmitter to ELRS 4.x first, then run voxl-elrs update --allow-major on the VOXL (voxl-elrs 1.3.9 or newer). A 4.x receiver does not bind or link with a 3.x transmitter, so move both or neither. The M0220 transceiver runs ELRS v4+ by default.

VOXL SDK Support

SDK 1.4.1 or newer required. For VOXL SDK usage, please see voxl-elrs.

Dimensions

The board is 33 mm x 23 mm with a 1.03 mm thick PCB. It has no mounting holes.

3D Drawings

3D STEP File

Features

Hardware

Hardware Block Diagram

Connectors

Summary

Hover a connector to identify it — click to jump to its details.

J4 - Header Solder Pads

J1 - ANT1

RF ANT1 path (915MHz).

J2 - ANT2

RF ANT2 path (915MHz).

S1 - Bind button

S1 only works while the receiver has no link to a transmitter. Presses are ignored while a link is up.

The receiver also enters bind mode when it is powered on three times in a row, switching it off within 2 seconds the first two times, or from the VOXL with:

voxl-elrs bind

After a 12-second reset the receiver will not link until it is bound again. Power-cycle it (ELRS 4.x firmware reboots on its own), then re-apply the vehicle’s settings from the VOXL and bind it again as above:

voxl-elrs configure

D1 - Green LED

Solid when bound.

D2 - Red LED

Status LED, follows ELRS standards

A constant slow blink means the receiver is not connected to a transmitter. The LED turns solid once a link is established. On a vehicle, this is the red light that keeps blinking until the transmitter is powered on and connected.

Programming Test Points

The bottom of the board has 1 mm test pads for SWD programming and debug. Normal firmware updates go over the J4 UART with voxl-elrs. The pads are only needed to recover a board whose bootloader no longer responds, using an ST-Link or J-Link.

Power the board with 5V on J4 while probing. Do not feed power into TP4.

User Guides

VOXL SDK

For VOXL SDK usage, please see voxl-elrs.

Also see the M0184 Software User Guide.

VOXL 2 Wiring Guide (M0054)

List of Certifications

FCC US radio compliance: For evaluation only; not FCC approved for resale