de_mavlink Configuration File

A file called de_mavlink.config.module.json exists in /home/pi/drone_engage/de_mavlink/ This file is written in JSON format. However, you can still add comments to the file. To those who do not know JSON just consider it a text file that you need to edit only few lines in it.

Accessing the Configuration File

Login to your Raspberry-PI board using ssh.

ssh pi@raspberry_pi_ip_address

and go to the file

cd /home/pi/drone_engage/de_mavlink/
ls

and open the file

nano de_mavlink.config.module.json

Fields Meaning

module_id

Just a name for your module
Example: “FCB_CTRL”

s2s_udp_target_ip

Points to de_comm listening IP
Example: “127.0.0.1”

s2s_udp_target_port

de_comm listening port
Example: “60000”

s2s_udp_listening_ip

This module’s listening IP
Example: “127.0.0.1”

s2s_udp_listening_port

This module’s listening port
Example: “61003”

s2s_udp_packet_size

UDP packet size
Example: “8192”

fcb_connection_uri

Connection to FCB board
Example: See examples below

default_optimization_level

Telemetry optimization 0-3
Example: 2

udp_proxy_enabled

Enable UDP telemetry
Example: false

udp_proxy_fixed_port

Fixed UDP port (optional)
Example: 15412

read_only_mode

Block all commands from WebClient
Example: false

logger_enabled

Enable logging to Logs folder
Example: true

logger_debug

Enable debug logging
Example: false

message_timeouts

MAVLink message rate control
Example: See below

event_fire_channel

Event fire channel
Example: 16

event_wait_channel

Event wait channel
Example: 15

rc_block_channel

RC block channel (1-8, -1=off)
Example: -1

mavlink_ids

MAVLink ID configuration
Example: See below

rc_channels

RC channel configuration
Example: See below

follow_me

Follow Me PID settings
Example: See below

Connection Examples

Connecting via TCP:

{
"fcb_connection_uri": 
{
"type": "tcp",
"ip": "127.0.0.1",
"port": 7600
}
}

Connecting via UDP:

{
"fcb_connection_uri": 
{
"type": "udp",
"ip": "0.0.0.0",
"port": 14551
}
}

This connection is straightforward using UDP. This is suitable when connecting DroneEngage to boards like OBAL via OTG Ethernet.

Connecting to a Serial Port:

Static Port:

{
"fcb_connection_uri":
{
"type": "serial",
"port": "/dev/ttyUSB1",
"baudrate": 115200
}
}

Dynamic Port Search:

{
"fcb_connection_uri":
{
"type": "serial",
"port": "/dev/ttyUSB",
"baudrate": 115200,
"dynamic": true
}
}

The dynamic field will make the module search for a valid mavlink port from /dev/ttyUSB0 to /dev/ttyUSB10. So even if you unplug and plug it again and the USB appeared on different address, the module will find it. This feature is developed to be able to detect mavlink port from Scan port.

baudrate has to match the baudrate defined in FCB. You can open GSC and configure mavlink parameters.

Important: You need to connect TX of RPI to RX of the FCB and vice-versa.

Important: If you want to use the OTG USB port make sure you run rasp-config and disable shell but keep serial port enabled.

MAVLink IDs Configuration

"mavlink_ids": {
    "de_mavlink_gcs_id": 255,
    "only_allow_ardupilot_compid": 0,
    "only_allow_ardupilot_sysid": 0
}

de_mavlink_gcs_id: Local GCS system ID (255 = default, -1 = disable heartbeat)
only_allow_ardupilot_compid: Only receive mavlinks from specified component ID (0 = no restriction)
only_allow_ardupilot_sysid: Only receive mavlinks from specified system ID (0 = no restriction)

RC Channels Configuration

Used for Gamepad control via Drone-Engage Web Client. Determine channels enabled, reverse, max & min PWM range.

"rc_channels": {
    "rc_smart_channels": {
        "active": true,
        "rc_channel_enabled": [1, 1, 1, 1],
        "rc_channel_limits_max": [2000, 2000, 1750, 2000],
        "rc_channel_limits_min": [1000, 1000, 1300, 1000]
    },
    "rc_channel_enabled": [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
    "rc_channel_reverse": [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
    "rc_channel_limits_max": [1850, 2000, 1750, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000, 2000],
    "rc_channel_limits_min": [1150, 1000, 1300, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000]
}

rc_smart_channels: Optional but recommended settings for ROLL-PITCH-THR-YAW regardless of actual settings on ardupilot
rc_channel_enabled: Array indicating which channels are active (1 = enabled, 0 = disabled)
rc_channel_reverse: Array indicating which channels are reversed (1 = normal, -1 = reversed)
rc_channel_limits_max/min: PWM limits for each channel

Follow Me Configuration

PID and Expo settings for autonomous tracking functionality:

"follow_me": {
    "PID_P_X": 1.0,
    "PID_P_Y": 1.0,
    "PID_I_X": 0.00,
    "PID_I_Y": 0.00,
    "expo_factor": 0.5,
    "deadband": 0.1,
    "rate_limit": 0.1
}

PID_P_X/Y: Proportional gain for X/Y axis tracking (0.1-5.0)
PID_I_X/Y: Integral gain for X/Y axis tracking (0.0-1.0)
expo_factor: Exponential curve for response (0.0-1.0)
deadband: Deadband threshold (0.0-0.5)
rate_limit: Max rate change per second (0.05-0.2)

Message Timeouts

The message_timeouts section controls the rate at which different MAVLink messages are sent in telemetry mode. Each message type has an array of four values representing different optimization levels (0-3), where 0 is maximum bandwidth and 3 is minimum bandwidth.

Example configuration:

"message_timeouts": {
    "0": [0, 1000, 2000, 3000],      // HEARTBEAT
    "24": [0, 800, 1000, 2000],     // GPS_RAW_INT
    "30": [0, 250, 1000, 2000],     // ATTITUDE
    "33": [0, 250, 1000, 2000],     // GLOBAL_POSITION_INT
    "74": [0, 500, 1000, 2000]      // VFR_HUD
}

The array format is [level_0, level_1, level_2, level_3] where each value represents the timeout in milliseconds for that optimization level.