Setting Heartbeats

Joints can be set to publish data at a set frequency using heartbeat packets.

Up to 10 packets can be set a a heartbeat per device. Frequency can be set to a whole number between 0 - 255 Hz.

Warning

Devices have been tested to support a maximum of 4 heartbeat packets at 255 Hz. Behaviour is undefined for values greater than this.

The following is an example of setting the heartbeat over a UDP Connection.

"""bplprotocol/examples/set_heartbeat.py"""
import time

from bplprotocol import BPLProtocol, PacketID, PacketReader

import socket

MANIPULATOR_IP_ADDRESS = "192.168.2.4"
MANIPULATOR_PORT = 6789

HEARTBEAT_PACKETS = [PacketID.POSITION, PacketID.VELOCITY, 0, 0, 0, 0, 0, 0, 0, 0]

DEVICE_IDS = [1, 2, 3, 4, 5, 6, 7]

FREQUENCY = 10

if __name__ == '__main__':

    manipulator_address = (MANIPULATOR_IP_ADDRESS, MANIPULATOR_PORT)
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    sock.settimeout(0)

    packet_to_send = b''

    for device_id in DEVICE_IDS:

        heartbeat_packets_set = BPLProtocol.encode_packet(device_id, PacketID.HEARTBEAT_SET, bytes(HEARTBEAT_PACKETS))
        sock.sendto(heartbeat_packets_set, manipulator_address)

        heartbeat_frequency_set = BPLProtocol.encode_packet(device_id, PacketID.HEARTBEAT_FREQUENCY, bytes([FREQUENCY]))
        sock.sendto(heartbeat_frequency_set, manipulator_address)

        print(f"Heartbeat set for Device 0x{device_id:X}")

The set heartbeat packets are sent automatically at the specified frequency. They can be read by listening to the UDP Socket.

    # Read the corresponding packets from the TX2.

    positions = ["-"] * len(DEVICE_IDS)
    pr = PacketReader()
    while True:
        try:
            recv_bytes, address = sock.recvfrom(4096)
        except BaseException:
            recv_bytes = b''

        if recv_bytes:
            packets = pr.receive_bytes(recv_bytes)

            for device_id, packet_id, data in packets:
                if packet_id == PacketID.POSITION:
                    position = BPLProtocol.decode_floats(data)[0]