Specifications

  • Ublox ZED-F9P GPS Receiver

    • Ultracap backup power for fast (hot-start) restarts

    • EMI shield over receiver for improved EMI immunity

  • IST8310 Magnetometer

  • Safety-switch and safety LED

  • RGB LEDs for status indication

    • NCP5623CMUTBG I2C Driver

  • BMP388 Baro on I2C bus

  • External, active antenna (Maxtena M7HCT)

    • SMA connector

  • STM32 MCU for future CAN-based communication

    • FW updates through USB connector

  • Connectivity:

    • USB-C

      • 2-way USB Switch to MCU and F9P

    • SMA for active antenna (20mA max)

    • 4-pin CAN Bus (dronecode compliant)

    • 8-pin UART/I2C

  • Power:

    • Input from either (diode OR'd):

      • USB (5V)

      • CAN (4.7 to 25.2V)

      • UART (4.7 to 25.2V)

    • Power Consumption <1W

RTK Performance over range

The performance of RTK over long distances is typically limited by:

  • Telemetry link: You must have a telemetry link between the aircraft and ground station,

  • RTK degradation over distance: As the aircraft moves away from the base station, the RTK accuracy will degrade. The F9P RTK GPS receiver spec is 0.01m CEP (Circular Error Probability) + 1ppm for both vertical and horizontal.

    • For example, at 10km distance from base station, the typical accuracy would be 0.01m + (1km * 1/1,000,000) = 0.02m CEP

Mechanical Dimensions

Prerequisites

For use on Alta, the following is necessary:

  • AltaX

  • Alta SW 1.3 or above

  • Datalink (FRX Pro recommended)

  • Computer (Mac or Windows) running Alta QGC 1.3 or above

  • Sturdy mount for base stations GPS. Tripod with 1/4-20 mount is recommended

I2C Address Table

Description

PN

I2C Address (7-bit)

RGB LED Driver

NCP5623C

011 1001 ($39)

Barometer

BMP388

111 0111 ($77)

Magnetometer

IST8310

000 1110 ($0E)

Connector Pinout

CAN Ports - GH-4 Pin

Peripheral CANbus for future expansion.

Pin

Signal

Voltage (V)

1

VCC

+5V to 25.2V

2

CAN_H

+5V

3

CAN_L

+5V

4

GND

GND

UART/I2C Ports - GH-8 Pin

Peripheral CANbus for future expansion.

Pin

Signal

Signal Notes

1

VCC

+5V to 25.2V

2

SERIAL: FC to GPS

3.3V TTL

3

SERIAL: GPS to FC

3.3V TTL

4

I2C-SCL

5

I2C-SDA

6

SAFETY SWITCH

3.3V = PRESSED

0V = NOT PRESSED

4.7k pull-down

7

SAFETY LED

3.3V, pull low to turn on LED. 20mA sink

8

GND

GND

GPS Antenna Compatibility

The following antennas have been tested with the Freefly RTK GPS module:

  • Maxtena M7HCT

  • UBlox ANN-MB multi-band antenna

The Freefly RTK modules are shipped with Maxtena M7HCT multiband antennas. However, the GPS is compatible with other SMA, L1/L2 multiband antennas.

Sensor Rotation

The IST8310 defines its coordinate system using left-hand rule, which is corrected in PX4 to be right-hand. Orientation is shown below in both native and PX4-corrected coordinates.

AltaX Orientation

When installed on AltaX, the PX4 orientation is with respect to the front-left vertical mounting surface. In other words, when installed on the front-left (where the standard GPS is installed), the "external mag" orientation should be set to Yaw 0° (ie, No rotation). When installed on the diagonal side (rear-right), the orientation should be set to Yaw 180°.