Configure the LR900 915 MHz Radio with MicoAssistant

MicoAssistant is a free, browser-based configuration tool for the LR900 telemetry radio. It runs entirely in Chrome or Edge — nothing to install — and lets you read and change every setting on the radio over USB. This guide explains what each parameter does, then gives copy-paste settings for the most common setups, from using the radio as a generic 915 MHz serial bridge to a full ArduPilot or PX4 telemetry link.

Written by the Robofusion engineering team — the first complete, plain-English walkthrough of the LR900's web configurator.

Which models this covers

This guide is written for the LR900-F and LR900-P. They are used identically and differ only in transmit power (the -P is the higher-power version). The LR900-A works the same way in the tool, with two differences: it doesn't support FHSS frequency-hopping, and it uses the CH340 USB driver instead of the CP2102.

Do you even need to configure it?

For most people, no. Out of the box, a pair of LR900 radios is already paired and ready to use for the two most common jobs — just power them up:

• As a plain serial link (passthrough) — anything you send into one radio comes out the other. Drop it in where a wired serial cable would go.
• As ArduPilot / PX4 telemetry — wire it to the flight controller's TELEM port; the two radios link up on power-up.

The only thing you may need to match is the baud rate to your device (factory default is 57,600). Open MicoAssistant only if you want to: reach longer range (FHSS), run several radio pairs near each other, or use a different baud rate. If none of that applies, you can stop here.

Here's the factory state at a glance:

Parameter	Default	Change it only if…
Work Mode	Duplex	…you're building a one-to-many RTK link
Speed Mode	High (2.1 KB/s)	…you need more range and can accept less data
TX Power	High	…you want to save power on a bench/indoor test
Freq Mode	Auto	…you want frequency-hopping or a fixed channel
Module Addr	1000	…you run more than one radio pair nearby
UART Baud	57,600	…your device uses a different baud

Before you start

• A Chrome or Edge browser (MicoAssistant uses the Web Serial API; Firefox and Safari will not work).
• A way to plug the radio into your computer. Every radio ships with a USB-A → USB-C adapter (the black adapter shown above) — fit it onto the radio and plug it straight into any USB port on your computer. No separate cable is required. (A USB-C cable also works if you prefer to use one; it isn't included.)
• The USB driver installed — CP2102 for the LR900-F/P, CH340 for the LR900-A. If you've never connected the radio before, do this first: CP2102 Driver Installation (Windows).
• The radio itself — an LR900-F or LR900-P. (The configurator also supports the rest of the LR-series: LR24-F/P, LR900-A, LR868-F, TRS, MSTAR24.)

Step 1 — Connect the radio

Open MicoAssistant and go to the Overview tab.

1. Plug the radio into your computer using the included USB-A → USB-C adapter.
2. Turn on the Radio Config toggle. This is the single most important step — it tells the tool you're configuring a radio module, not reading a sensor. Switch it on before you connect.
3. Click Change Port and pick the radio's serial port (the CP210x / CH340 device). You'll see "OK Port selected" in green.
4. Leave Baud Rate at 57,600 (the radio's default USB baud).
5. Click Connect. The status dot at the top-left turns to a green Connected.

When you click Change Port, the browser shows its serial-port chooser. Pick the CP2102 (LR900-F/P) or CH340 (LR900-A) device, then confirm:

Configuring both radios

Configure one radio at a time — set up the second the same way afterward. Each radio connects to your computer through the USB-A → USB-C adapter. In normal flight-controller use, connect the radio to the flight controller through the GH1.25 4-pin UART port. The USB-C port is for connecting the radio to a computer or supported host device for configuration or ground-station use — it is not used to directly wire the radio to a flight controller.

Step 2 — Understand the parameters

Open the Params tab. You'll see the full parameter set for the radio, labelled Telemetry Radio – LR900. Each setting is a dropdown — here are all of them opened, so you can see every option at a glance:

Here is what every setting does:

Parameter	What it controls	Options	Default
Work Mode	The direction of data flow. Duplex is two-way (normal telemetry). The broadcast modes are one-way and are used for one-to-many links such as an RTK base feeding several rovers.	Duplex · Broadcast TX · Broadcast RX	Duplex
Speed Mode	The over-the-air data rate. Faster moves more data; slower reaches further. High is right for flight-controller telemetry.	Low (0.4 KB/s) · Medium (1.1 KB/s) · High (2.1 KB/s)	High
TX Power	Transmit power. Higher power means more range but more current draw. The actual maximum depends on the model (LR900-A ≈ 160 mW, F ≈ 500 mW, P ≈ 1000 mW).	Low · Medium · High	High
Freq Mode	How the operating frequency is chosen. Auto just works. Manual lets you pin a channel. The two FHSS modes turn on frequency-hopping for better interference resistance (see below).	Manual · Auto · FHSS Ground · FHSS Air	Auto
Freq Channel	The fixed channel, only active in Manual mode (greyed out otherwise). Values 0–25 map across 890–915 MHz.	0–25	0
Module Addr	The pairing / network ID. Two radios only talk if their Module Addresses match. Change it to run several independent pairs nearby.	1–30000	1000
UART Baud Rate	Baud of the TTL serial port that wires to your flight controller. Must match the flight controller's serial baud (SERIALx_BAUD / SER_TELn_BAUD).	9,600 · 19,200 · 38,400 · 57,600 · 115,200	57,600
USB Baud Rate	Baud of the USB-C port to your computer / ground station.	57,600 · 115,200	57,600

A note on FHSS (frequency hopping)

In a noisy 915 MHz environment, frequency-hopping spreads your link across many channels so a single source of interference can't block it. To use it, the two ends take different roles: the radio on the aircraft is set to FHSS Air, and the radio on the computer to FHSS Ground. FHSS also raises the downlink (aircraft → ground) rate, up to about 3.2 KB/s. Note the LR900-A does not support FHSS — use Auto on that model.

Step 3 — Save your changes

After changing values, click Save to Device (top-right of the Params panel). The Default Params button next to it resets everything to factory settings.

Configure both radios

A link is a pair. Whatever you change that affects pairing — Module Address, Freq Mode, Speed Mode — must be set compatibly on both radios, or they won't connect.

Typical setups (copy-paste)

The LR900 is used two broad ways: as a plain long-range serial link between any two devices, and as a flight-controller telemetry radio. Here's how to set up each — pick the one that matches what you're doing.

Setup 1 — Generic 915 MHz serial link

The LR900 is a transparent UART bridge: whatever bytes go into one radio's serial port come out the other. That makes it a drop-in, long-range replacement for a wired serial connection — sensor backhaul, a microcontroller-to-PC link, an RTK base-to-rover data feed, and similar 915 MHz serial-link uses. Plenty of people buy these radios for exactly this, with no flight controller involved.

Setting	Both radios	Notes
Work Mode	Duplex	Use the broadcast modes for one-to-many (e.g. one RTK base → several rovers)
UART Baud	match your device	set both ends to your device's baud rate
Module Addr	same on both	unique per link if several are nearby

Setup 2 — Basic ArduPilot / PX4 telemetry link

The simplest drone case. Both radios keep the factory defaults; they pair on power-up (LED goes solid). You don't even need MicoAssistant for this — just wire it up and follow the flight-controller side: ArduPilot setup · PX4 setup.

Setting	Both radios
Work Mode	Duplex
Speed Mode	High
Freq Mode	Auto
Module Addr	1000
UART Baud	57600 (match your FC)

Setup 3 — Best reliability for ArduPilot / PX4 telemetry: FHSS

Frequency-hopping (FHSS) spreads the link across many channels, improving resistance to interference and overall link reliability. It's the recommended mode for MAVLink flight-controller telemetry, where High speed is appropriate.

Setting	Aircraft radio	Ground (PC) radio
Freq Mode	FHSS Air	FHSS Ground
TX Power	High	High
Speed Mode	High	High
Module Addr	1000 (same on both)	1000 (same on both)

For non-MAVLink serial links where the data rate is low, a slower Medium or Low Speed Mode may reach further — but test with your actual payload, since real-world range depends on antennas, terrain and interference.

Setup 4 — Several aircraft / links at once

Give each pair its own Module Address so they don't interfere. Optionally switch to Manual Freq Mode and assign each pair a different Freq Channel for extra separation.

Pair	Module Addr	(Optional) Freq Channel
Link 1	1001	5
Link 2	1002	12
Link 3	1003	20

Step 4 — Verify the link

Reconnect the second radio, or switch to the Log tab to watch raw serial traffic. Bytes scrolling in the RX — Received pane confirm data is flowing across the link; on the radio itself, a solid LED means it's paired and connected.

Troubleshooting & FAQ

The browser won't open a port / "Web Serial not supported." Use Chrome or Edge — Firefox and Safari don't support the Web Serial API MicoAssistant relies on.

No port appears when I click Change Port. The USB driver isn't installed. Install the CP2102 driver (LR900-F/P) or the CH340 driver (LR900-A), then try again.

The two radios won't pair. Check that both have the same Module Address, a compatible Freq Mode, and the same Speed Mode. If you're using FHSS, one end must be FHSS Air and the other FHSS Ground.

Do both radios need an "air" and a "ground" end? Only in FHSS mode. In the default Auto mode the two ends are interchangeable.

Can I mix an LR900-A with an LR900-F or -P? Yes — the variants interoperate. The link range is limited by whichever end has the lower transmit power, and remember the LR900-A can't do FHSS.

What baud should my flight controller use? Match it to the radio's UART Baud Rate (default 57600). In ArduPilot that's SERIALx_BAUD = 57; in PX4 it's SER_TELn_BAUD = 57600.

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Written and maintained by the Robofusion engineering team.