Holybro Microhard Telemetry Radio integrates a microhard Pico Series RF module, which is capable of delivering high-performance wireless serial communications in robust topologies, such as Point to Point, Point to Multipoint, and secure Mesh (Mesh only available on P900).

It uses frequency hopping spread spectrum (FHSS) technology, providing reliable wireless asynchronous data transfer between most equipment types that employ a serial interface. Fixed frequency is available on the P840 version. The radio is configured using AT commands through the Data port or using the PicoConfig application through the Diagnostic Port.

With the new V2 design, the UART to USB adapter is no longer needed for parameter configuration. A dedicated switch is added to the board for easy mode change between standard data transmission mode to configuration mode.

P900 Radio operates within the 902-928 MHz ISM frequency band, while the P840 operates within 840-845Mhz, and P400 operates within 410-480MHz. You can select your radio based on your country's available frequency band.

Feature

• USB Type-C port, integrated USB to UART converter

• 6-position JST-GH connector can be directly connected to the TELEM port on various flight controllers.

• High voltage BEC onboard, supports DC7~35V voltage supply

• UART transmission LED indicator

Legacy Version:

V2:

Enable CTS/RTS

1）Connect a USB cable from the PC USB port to the USB TYPE-C of the module.

2 ) Launch a terminal communications program (e.g. HyperTerminal) and configure for 9600 bps, 8 data bits, No parity, 1 stop bit (8N1), no flow control.

3 ) press and hold the CONFIG button and apply power to the module.

4 ) release the CONFIG button

5 ) On power up the terminal session window should show “NO CARRIER OK” as seen below:

6 ) the P900 is now in command mode, and AT commands can be used to configure or query the settings.

7 ) Type in AT&K3 and press Enter will enable CTS/RTS handshaking.

8 ) Type in AT&W and press Enter to save the configuration to the NVRAM of the module. Then, the configuration will not be lost after the power off.

Confirm Configuration

9 ) Power off and redo step1~5.

10 ) Type in AT&V and press Enter will display the current configuration as seen below: (Handshaking & K3 means CTS and RTS are already enabled.)

Disable CTS/RTS

11 ) redo step1~5.

12 ) Type in AT&K0 and press Enter will disable CTS/RTS handshaking.

13) Type in AT&W and press Enter to save the configuration to the NVRAM of the module.

Confirm Configuration

14 ) Power off and redo step1~5.

15 ) Type in AT&V and press Enter will display the current configuration as seen below: (Handshaking & K0 means CTS and RTS are disabled.)

Sample Wiring Diagram

Point to Multipoint Connection Using Microhard Radio

Telemetry Radio Setup

First, Select one of the Radios as the Master, and the other Radios as the Remote. Use the to set the Master to PMP Master mode, and change the baud rate to 57600. As shown in the figure below:

1. Select PMP Master

2. Click Default Unit

3. Select 57600 baud rate

4. Click PGM/Save.

Then, set all the Remote Radios to PMP Remote mode, and change the baud rate to 57600. As shown below:

1. Select PMP Remote

2. Click Default Unit

3. Confirm that the Network Address is consistent with the Master

4. Set a unique Unit Address different for each Remote Radio.

Flight Controller Settings

Connect the flight controller via USB and set an ID for each flight controller that is different from other flight controllers.

For PX4 firmware, the MAV_SYS_ID parameter should be set

For Ardupilot firmware, the SYSID_THISMAV parameter should be set

Use the Master Radio to connect to the ground station (QGC/MissionPlanner), and the Remote Radio to connect to the flight controllers. If using RTK system, wait for the Base Survey-in to distribute the RTCM data of a Base to multiple Rover after powering on.

Specification

Power Port (4-position JST-GH, XT30 for V2 design)

The input Voltage range is 7-35 VDC. The Radio must be powered by this Power Port. Please connect to a power supply when in use and during configuration.

Config Button

Holding this button while powering up the radio will boot the unit into COMMAND mode: the default serial interface will be active and temporarily set to operate at its default serial settings of 9600/8/N/1.

USB

USB Type-C Port with internal USB to Serial Converter. Holybro Microhard Radio’s USB port provides access to the Serial data Port. That means you can connect the Holybro Microhard Radio to your ground station via the USB port directly. USB VBus only powers the USB to Serial chip, and does not power the Radio.

USB SWITCH Button(Only for V2 design)

When the Radio is powered on, if the USB Type-C connection is detected, the USB port provides access to the serial data Port of the Radio by default. Holding down the SWITCH button (approximately 3 seconds) until the DIAG(diagnostics) LED comes on, the USB port switches access to the diagnostic Port of the Radio. Holding down the SWITCH button (approximately 3 seconds) again until the DIAG LED goes out, the USB port now switches back to the Serial data Port of the Radio.

Data Port (6-position JST-GH)

This data Port is used to connect to the telemetry port of your flight controller. When the USB Type-C port isn't connected, this port will transfer serial data automatically. When USB Type-C is plugged in, this connector is floating. Data Port does not power the Radio.

Diagnostic Port (4-position JST SH only available for V1 design)

This connector connects to the Diagnostic Port. If you use the PicoConfig application or special diagnostic commands to configure the Radio, you should connect to this port. Diagnostic Port is 3.3V logic level compatible. A USB to Serial board is needed for connecting the radio to your computer.

Data Port

Diagnostic Port

Power Port

Holybro Microhard Radio have been configured to Point to Point Operating Mode and 57600 Serial Baud Rate in factory. Using these parameters, the Radio can communicates successfully with the Pixhawk series flight controller. After Firmware Update or resetting the Radio, you can re-config them as following.

In Point to Point operating modes, there must be a master to provide network synchronization for the system, so one Radio should be configured to PP Master and another should be configured to PP Remote. Refer to Operating Manual for the detail information of Radio Configuration.

Holybro Microhard V1 Radio has 6 status LEDs, there are three blue, two orange, and one green LEDs.

Holybro Microhard V2 Radio has 7 status LEDs, there are three blue, three orange, and one green LEDs.

The meaning of the different LEDs is:

Power LED (Green)

This LED will illuminate when the Radio is connected to a power source (7-35VDC).

TX LED (Orange)

When illuminated, this LED indicates that the Radio is transmitting data over the air.

RX LED (Orange)

This LED indicates that the Radio is synchronized and has received valid packets.

DIAG LED (Orange, V2 ONLY)

This LED indicates the connectivity of the USB port. When illuminated, the USB port provides access to the diagnostic port of the radio. When turned off, the USB port provides access to the serial data port of the radio.

RSSI LEDs (3x Blue)

As the received signal strength increases, starting with the furthest left, the number of active RSSI LEDs increases. Signal strength is calculated based on the last four valid received packets with correct CRC. The value of RSSI is reported in S123.

RSSI LEDs(blue) - indicate the receive signal strength.