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Example Project Spektrum RC with Betaflight and Simblee

Aim of this Project is to control a drone from the computer using a joystick. On Pc side Ros is used to read data from a joystick and send it over BLE to the simblee. The Simblee then generates the Spektrum 2048 frame (only 7 channels are used) which is then sent over the UART to the flight controller.

The Simblee is fail silent which means if no data is received over BLE he don’t output anything to the flight controller. This gives the flight controller the chance to go in failsafe mode.

Components used:

Component
Flightcontroller Matek F405 STD with Betaflight 3.2.2
Bluetooth Modul Drone Simblee
USB Bluetooth Dongle LogiLink-BT0015
OS Ubuntu-Mate 18.04
ROS-Version melodic,1.14.3
Joystick Sony DualShock 3

There a two different implementation for the BLE communication available. The first is based on the Source of the gatttool directly . The Second is based on pygatt which also uses gattool. Both clients implement a reconnect feature if the connection is lost. (the python client reconnects only if he can not sent data, or during first connect)

(Note: currently there is a bug in the first implementation where after a number of data sent no more data are sent.)

Setting up libgatt

Install the modified version of libgatt.

git clone https://github.com/ChristianHirsch/libgatt.git
cd libgatt
$ ./bootstrap
$ ./configure
$ make -j`nproc`
sudo make install

Setting up pygatt

sudo apt-get install python-pip
pip install pygatt

Install and Building the ROS Nodes:

  1. Create a new folder
mkdir -p bleWS/src
cd bleWS
  1. Clone this repository
git clone https://github.com/tuw-cpsg/ble_client_ros.git
mv ble_client_ros/ src
  1. Create a new catkin workspace
source /opt/ros/melodic/setup.bash
catkin_make
source devel/setup.bash

Using the ROS Nodes:

Setup Nodes

There are two launch scripts for launching the example.

script
drone.launch launches the cpp node based on gattlib
python_drone.launch launches the python script droneControl.py based on pygatt

in both files you need too make adjustments to match your controller input device and your Bluetooth Device Address.

<param name="joy_node/dev"  value="/dev/input/js0" /> 
<param name="droneControl/device" value="C4:D0:0D:79:59:91" />

Launching the example

launch the python node

roslaunch ble_client_node python_drone.launch --screen

launch the cpp node.

roslaunch ble_client_node drone.launch --screen

If you get the error:

bleWS/devel/lib/ble_client_node/ble_client_node: error while loading shared libraries: libgatt.so.0

add the libgatt to the LD_LIBRARY_PATH

LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib

Simblee:

Simblee uses the arduino platform. The following code sent every 11ms a Spektrum frame over the UART.

#include <SimbleeBLE.h>
#define SPEKTRUM_DSMX_11 0xb2
#define SPEKTRUM_2048_CHANNEL_COUNT 12
#define SPEKTRUM_NEEDED_FRAME_INTERVAL     5000
#define SPEKTRUM_BAUDRATE 115200
#define MASK_2048_CHANID 0x7800 
#define MASK_2048_SXPOS 0x07FF 
#define SPEK_FRAME_SIZE 16

unsigned long startMillis; 
unsigned long currentMillis;
const unsigned long period = 11; 


uint8_t spekFrame[SPEK_FRAME_SIZE];
uint16_t spekChannelData[12];

uint16_t bledata[6] = {0, 1024, 1024, 1024, 0, 0};
bool send = true;

void setup() {
  override_uart_limit = true; 
  Serial.begin(SPEKTRUM_BAUDRATE,3,2);//baud rx tx
  startMillis = millis();  //initial start time 
  SimbleeBLE.deviceName = "Drone";
  SimbleeBLE.begin();
}



void loop() {
  currentMillis = millis(); 
  if (currentMillis - startMillis >= period)  {
    
    if(!send){     
      Serial.write(SPEKTRUM_DSMX_11); //start 
      Serial.write((uint8_t)00);      // missed frame count
  
      for(uint16_t i = 0; i< 7;i++){
        uint16_t data =  (i << 11)+(0 & MASK_2048_SXPOS);
        if(i<6){
          data = (i << 11)+(bledata[i] & MASK_2048_SXPOS);
        }
        
        Serial.write((uint8_t)(data >> 8));//Send Upper Byte first
        Serial.write((uint8_t)(data));// Send Lower Byte
        send = true;
      }
    }
    startMillis = currentMillis; 
  }
}

void SimbleeBLE_onReceive(char *dataBLE, int len){
  if(send){ 
    for(int i,e = 0;i<12 && i<len;i=i+2,e++){
      bledata[e]=(((uint16_t)dataBLE[i+1])<<8) + (uint16_t)dataBLE[i]; // little Endien
    } 
    send = false;
  }
}

TODO:

  • find bug in cpp node
  • send telemetry to ROS