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
GPS Origin Point
GPS coordinates reported from this base station are centered around a point 35mm from the base of the antenna.
Mechanical Dimensions
Prerequisites
For use on Alta, the following is necessary:
Alta X
Two RTK Modules (Rover and Base Station)
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
USB C cable
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.
Alta X Orientation
When installed on Alta X, 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°.
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