Python API

This repository provides templates for the development of the Python examples based on the AMBER UDP protocol, the number in the file name is the command number in UDP protocol.

UDP protocol link：https://github.com/MrAsana/AMBER_B1_ROS2/wiki/SDK-&-API---UDP-Ethernet-Protocol--for-controlling-&-programing .

First-Time Users

We recommend you getting started with cmd_04_single_move.py ,which allows you control multiple joint to move once by input their position ( unit of angle: rad, 1rad ≈ 57.296° ) .

Make sure you have read our UDP protocol .

Set IP address

Set your ROS Master's IP_ADDR in Line 11 .

Data structures(ctype structure)

We will explain these later.

We use Python ctypes structure to make everything matches C++ API, so c_uint16 == uint16_t in protocol .

_pack_ = 1 is for override structure align, no need to change in normal situation.

Prepare socket connection

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)               
s.bind(("0.0.0.0", 12321))

These are standard socket processes, no need to change in normal situation.

Prepare control data

Modify position and angles in in Line 42 :

from

payloadS = robot_joint_position(4, 44, 114514,0,0,0,0,0,0,0,0,1)

to

payloadS = robot_joint_position(4, 44, 114514,0,0,0,1.57,0,-1.57,0,0,1)

Type	Data	Example	Comment
c_uint16	cmd_no	4	Command Number, 4 : Single Joint move once
c_uint16	length	44	Length, 44 , Fixed value for Command 4
c_uint32	counter	114514	Correspondence code, you can choose any number you like
c_float	pos0	0	Joint 1 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos1	0	Joint 2 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos2	0	Joint 3 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos3	1.57	Joint 4 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos4	0	Joint 5 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos5	-1.57	Joint 6 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos6	0	Joint 7 target position, use radian measure, 1 rad ≈ 57.296°
c_float	pos7	0	Joint target position, which may use in future , irrelevant right now
c_float	time	1	Duration time to target, from current position to next position

Send data by socket

s.sendto(payloadS, (IP_ADDR, 25001))

Default port is 25001, no need to change in normal situation.

If everything is set up correctly, when you send these data by socket, joint 4 and joint 6 will rotate 90°(and -90° for joint 6), make sure the robot workspace is clear.

Prepare receive data from socket

data, addr = s.recvfrom(1024) 
print("Receiving: ", data.hex())

You will see raw data printed out in terminal, and you can easily convert raw data into ctypes struct and print out in terminal .

payloadR = robot_mode_data.from_buffer_copy(data)
print("Received: cmd_no={:d}, length={:d}, "
      "counter={:d}, respond={:d}".format(payloadR.cmd_no,
                                          payloadR.length,
                                          payloadR.counter,
                                          payloadR.respond, ))

Type	Data	Example	Comment
c_uint16	cmd_no	4	Command Number, 4
c_uint16	length	9	Length, 9, Fixed value
c_uint32	counter	114514	Correspondence code
c_uint8	respond	1	Flag, 0: Failure，1: Success

Terminal output for example

Sending: cmd_no=4, length=44, counter=114514,
pos0=0.000000,pos1=0.000000,pos2=0.000000,pos3=1.570000,pos4=0.000000,pos5=-1.570000,pos6=0.000000,pos7=0.000000,time=1.000000
Receiving:  0400090052bf010001
Received: cmd_no=4, length=9, counter=114514, respond=1