What i am trying to achieve is to have the Mega transmit mavlink commands to the TELEM1 port of the Pixhawk autopilot. Using the Mega as a ground station.
I have a code that appears to be working.
Inspecting the packets that i am sending with qGroundControl i get the following output :
(some of the params on heartbeat packet have been changed since the picture was taken).
I have connected the Mega to TELEM1 of Pixhawk as shown in the picture bellow
What i am trying to do with the resistors is a voltage divider because the Pixhawk is 3.3v for TX, RX but the Mega outputs 5V.
I have measured the voltage of TX0 on the Mega and it's 3.2 - 3.3 V with the circuit i have above.
But when sending data i do not see any significant drop to the voltage, it will drop to something like 3V from 3.2V. So i believe i am doing something wrong. How can the Pixhawk know when we have a logical 0 or 1 if the difference is only 0.2 Volts?
I am using the following code to test the connection.
#include "mavlink.h"
#define bRate 115200
void setup() {
Serial.begin(bRate);
}
void loop() {
command_heartbeat();
command_waypoint();
}
void command_heartbeat() {
int sysid = 1;
int compid = MAV_COMP_ID_MISSIONPLANNER;
uint8_t system_type = MAV_TYPE_GCS;
uint8_t autopilot_type = MAV_AUTOPILOT_INVALID;
uint8_t system_mode = 0;
uint32_t custom_mode = 0;
uint8_t system_state = 0;
mavlink_message_t msg;
uint8_t buf[MAVLINK_MAX_PACKET_LEN];
mavlink_msg_heartbeat_pack(sysid,compid, &msg, system_type, autopilot_type, system_mode, custom_mode, system_state);
uint16_t len = mavlink_msg_to_send_buffer(buf, &msg);
delay(1000);
Serial.write(buf, len);
}
void command_waypoint() {
uint8_t _target_system = 1; // Target drone id
uint8_t _target_component = 0; // Target component, 0 = all
uint16_t seq = 0; // Sequence is always set to 0
uint8_t frame = MAV_FRAME_GLOBAL; // Set target frame to global default
uint16_t command = MAV_CMD_NAV_WAYPOINT;
uint8_t current = 2; // Guided mode waypoint
uint8_t autocontinue = 0; // Always 0
float param1 = 0; // Loiter time
float param2 = 1; // Acceptable range from target - radius in meters
float param3 = 0; // Pass through waypoint
float param4 = 0; // Desired yaw angle
float x = 52.464217; // Latitude - degrees
float y = -1.280222; // Longitude - degrees
float z = 200; // Altitude - meters
mavlink_message_t msg;
uint8_t buf[MAVLINK_MAX_PACKET_LEN];
mavlink_msg_mission_item_pack(1,1, &msg, _target_system, _target_component, seq, frame, command, current, autocontinue, param1, param2, param3, param4, x, y, z);
uint16_t len = mavlink_msg_to_send_buffer(buf, &msg);
delay(1000);
Serial.write(buf, len);
}
Running this code i do not see any changes to the Pixhawk, the rotors do not start to spin, reading the waypoints from the pixhawk using mission planner does not show the waypoint i am trying to send.
I am unsure as to what the drone id should be.
Both the Pixhawk and the Mega are powered by their usb connected to a computer.
Any help would be greatly appreciated. Thank you for your time.
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