Robobot MQTT-client - Revision history

Jca: /* Behave */

2026-01-20T13:07:05Z

Behave

← Older revision		Revision as of 15:07, 20 January 2026
Line 208:		Line 208:
	topic: "robobot/cmd/ti", payload: "rc 0.1 0.5"		topic: "robobot/cmd/ti", payload: "rc 0.1 0.5"

	where the topic ''robobot/cmd/ti'' indicates that it is for the ''teensy_interface''. The parameters are a forward velocity of 0.1 m/s and a turn rate of 0.5 rad/s (positive os ~~CCV~~).		where the topic ''robobot/cmd/ti'' indicates that it is for the ''teensy_interface''. The parameters are a forward velocity of 0.1 m/s and a turn rate of 0.5 rad/s (positive os CCW).

	The related Python command is		The related Python command is

Jca: /* Main loop */

2026-01-20T13:06:32Z

Main loop

← Older revision		Revision as of 15:06, 20 January 2026
Line 90:		Line 90:
	print("% Main Terminated")		print("% Main Terminated")

	The system is set up at the bottom of the code. The main setup parameter is the robot IP. If running on the Raspberry Pi, this should be ''127.0.0.1''; otherwise, it must be the robot's IP as displayed by the robot.		The system is set up at the bottom of the code. The main setup parameter is the robot's IP address. If running on the Raspberry Pi, this should be ''127.0.0.1''; otherwise, it must be the robot's IP as displayed by the robot.

	At the top are the other modules imported.		At the top are the other modules imported.
Line 97:		Line 97:

	The commands to the robot, the MQTT messages, are a service function call:		The commands to the robot, the MQTT messages, are a service function call:
	service.send(~~service.topicCmd +~~ "ti~~/rc~~","0.25 0") # go straight		service.send("robobot/cmd/ti","rc 0.25 0") # go straight
	The first parameter (''~~service.topicCmd +~~ "ti~~/rc~~"'') is the topic~~. The service module has the system~~ and ~~function part of the topic. Then, "''ti/rc''" is added to indicate~~ that ~~this~~ is for the ''teensy_interface~~'' and a remote-control message~~.		The first parameter (''"robobot/cmd/ti"'') is the MQTT topic and indicates that it is a command for the ti (teensy_interface).

	The second parameter (''"0.25 0"'') is the ~~desired~~ forward velocity in meters per second and the turn rate in radians per second (positive is ~~CCV~~).		The second parameter (''"rc 0.25 0"'') is the command, here rc (remote control), forward velocity in meters per second and the turn rate in radians per second (positive is CCW (counter-clockwise).

	A delay, ''t.sleep(0.1),'' is inserted in the loop to save power and give the processor more time to handle incoming MQTT messages.		A delay, ''t.sleep(0.1),'' is inserted in the loop to save power and give the processor more time to handle incoming MQTT messages.

Jca: /* Behave */

2026-01-20T13:00:09Z

Behave

← Older revision		Revision as of 15:00, 20 January 2026
Line 206:		Line 206:
	The ''Behave'' block sends a 'remote-control' MQTT message, like:		The ''Behave'' block sends a 'remote-control' MQTT message, like:

	robobot/cmd/ti/rc 0.1 0.5		topic: "robobot/cmd/ti", payload: "rc 0.1 0.5"

	where the topic ''robobot/cmd/ti~~/rc~~'' indicates that it is for the ''teensy_interface~~'' and is a remote-control ''rc~~''. The parameters are a forward velocity of 0.1 m/s and a turn rate of 0.5 rad/s.		where the topic ''robobot/cmd/ti'' indicates that it is for the ''teensy_interface''. The parameters are a forward velocity of 0.1 m/s and a turn rate of 0.5 rad/s (positive os CCV).

	The related Python command is		The related Python command is

	service.send(~~service.topicCmd +~~ "ti~~/rc~~","0.1 0.5")		service.send("robobot/cmd/ti", "rc 0.1 0.5")

	=== MQTT ===		=== MQTT ===

Jca: /* Servo control */

2026-01-20T12:55:58Z

Servo control

← Older revision		Revision as of 14:55, 20 January 2026
Line 281:		Line 281:
	The servo can be controlled by a message directly to the Teensy		The servo can be controlled by a message directly to the Teensy

	robobot/drive/T0/servo 1 400 200		topic: "robobot/drive/T0", payload: "servo 1 400 200"

	where the topic ''robobot/drive/T0~~/servo~~'' is a topic ~~that~~ is transferred directly to the ~~teensy~~ as a ''servo 1 400 200'' command.		where the topic ''robobot/drive/T0'' is a topic where the payload is transferred directly to the Teensy as a ''servo 1 400 200'' command.

	The command parameters are ''1'' for servo number one and ''400'' for the position (range is ca. -800 to 800 (us). The third parameter, ''200'', is velocity, the number of values per second. If the starting position is zero and the destination is 400, it takes about 2 seconds to reach position 400.		The command parameters are ''1'' for servo number one and ''400'' for the position (range is ca. -800 to 800 (us). The third parameter, ''200'', is velocity, the number of values per second. If the starting position is zero and the destination is 400, it takes about 2 seconds to reach position 400.

Jca: /* Line detect */

2026-01-20T12:52:40Z

Line detect

← Older revision		Revision as of 14:52, 20 January 2026
Line 275:		Line 275:
	A forward velocity of zero will end the line drive.		A forward velocity of zero will end the line drive.

	Other detections are probably needed to achieve smooth line-following. The provided code uses only 8 values, from -3.5 to +3.5, ~~in steps~~ of 1.		Other detections are probably needed to achieve smooth line-following. The provided code uses only 8 values, from -3.5 (left) to +3.5 (right), with a step size of 1.

	== Servo control ==		== Servo control ==

Jca: /* Line detect */

2026-01-20T12:52:02Z

Line detect

← Older revision		Revision as of 14:52, 20 January 2026
Line 258:		Line 258:
	=== Line detect ===		=== Line detect ===

	~~There is a (basic)~~ line ~~detect~~ function ~~that uses~~ the centre of gravity ~~for~~ the bright part to determine the position of the tape line.		A line-detection function could use the centre of gravity of the bright part to determine the position of the tape line.
			Note that this is not the way the provided code works; it estimates the left and right edge positions.

	[[file:bode_set_a6_720_124.png \| 500px]]		[[file:bode_set_a6_720_124.png \| 500px]]
Line 265:		Line 266:
	The red curves show steady measurements, and the blue shows a situation with more variation.		The red curves show steady measurements, and the blue shows a situation with more variation.
	Sensor level 0 is black (no reflection). In this case, the background is about 600, i.e., rather bright but not as bright as the tape line (calibrated to 1000).		Sensor level 0 is black (no reflection). In this case, the background is about 600, i.e., rather bright but not as bright as the tape line (calibrated to 1000).
	The vertical lines show the ~~detector's estimate~~ of ~~the line~~ position.		The vertical lines show the "centre of gravity" position.
	Note the variation in measurements on the floor (a wooden floor with some variation).		Note the variation in measurements on the floor (a wooden floor with some variation).

	The line position is zero if the tape line is centred below the robot, between sensors 4 and 5. The value is the number of sensors away from the centre. The red line position measurement is about -0.6, and the blue is about +0.7.		The line position is zero if the tape line is centred below the robot, between sensors 4 and 5. The value is the number of sensors away from the centre. The red line position measurement is thus about -0.6, and the blue is about +0.7.

	For ~~every~~ update of the line sensor data, a new turn rate is calculated and published on the MQTT server~~, which~~ controls the wheels.		For each update to the line sensor data, a new turn rate is calculated and published to the MQTT server that controls the wheels.

	A forward velocity of zero will end the line drive.		A forward velocity of zero will end the line drive.

	Other detections ~~can be added~~, ~~such as line crossing~~ to ~~one side or line edge~~.		Other detections are probably needed to achieve smooth line-following. The provided code uses only 8 values, from -3.5 to +3.5, in steps of 1.

	== Servo control ==		== Servo control ==

Jca: /* Command line parameters */

2026-01-20T09:17:33Z

Command line parameters

← Older revision		Revision as of 11:17, 20 January 2026
Line 21:		Line 21:
	=== Command line parameters ===		=== Command line parameters ===

	The app has defined a few command line parameters, among these help:		The app has defined a few command-line parameters, among these is help:

	python3 mqtt-client.py --help		python3 mqtt-client.py --help
Line 34:		Line 34:
	'' -s, --silent Print less to console		'' -s, --silent Print less to console
	'' -n, --now Start drive now (do not wait for start button)		'' -n, --now Start drive now (do not wait for start button)
			'' -m, --meter Drive 1 m and stop
			'' -p, --pi Turn 180 degrees (Pi) and stop
			'' -u USESTATE, --usestate USESTATE
			Set mission state to this value

	The command line options include ~~some~~ sensor calibration. The distance sensor calibration is missing (but needed, see the [[Robobot_teensy_firmware]]).		The command-line options include sensor calibration. The distance sensor calibration is missing (but needed, see the [[Robobot_teensy_firmware]]).

	=== Main loop ===		=== Main loop ===

Jca: /* Servo control */

2025-02-19T08:20:47Z

Servo control

← Older revision		Revision as of 10:20, 19 February 2025
Line 278:		Line 278:
	robobot/drive/T0/servo 1 400 200		robobot/drive/T0/servo 1 400 200

	where the topic ''robobot/drive/t0/servo'' is a topic that is transferred directly to the teensy as a ''servo 1 400 200'' command.		where the topic ''robobot/drive/T0/servo'' is a topic that is transferred directly to the teensy as a ''servo 1 400 200'' command.

	The command parameters are ''1'' for servo number one and ''400'' for the position (range is ca. -800 to 800 (us). The third parameter, ''200'', is velocity, the number of values per second. If the starting position is zero and the destination is 400, it takes about 2 seconds to reach position 400.		The command parameters are ''1'' for servo number one and ''400'' for the position (range is ca. -800 to 800 (us). The third parameter, ''200'', is velocity, the number of values per second. If the starting position is zero and the destination is 400, it takes about 2 seconds to reach position 400.

Jca: /* Servo control */

2025-02-19T08:19:53Z

Servo control

← Older revision		Revision as of 10:19, 19 February 2025
Line 276:		Line 276:
	The servo can be controlled by a message directly to the Teensy		The servo can be controlled by a message directly to the Teensy

	robobot/drive/t0/servo 1 400 200		robobot/drive/T0/servo 1 400 200

	where the topic ''robobot/drive/t0/servo'' is a topic that is transferred directly to the teensy as a ''servo 1 400 200'' command.		where the topic ''robobot/drive/t0/servo'' is a topic that is transferred directly to the teensy as a ''servo 1 400 200'' command.

Jca: /* Line detect */

2025-02-02T11:27:33Z

Line detect

← Older revision		Revision as of 13:27, 2 February 2025
Line 264:		Line 264:
	Note the variation in measurements on the floor (a wooden floor with some variation).		Note the variation in measurements on the floor (a wooden floor with some variation).

	The line position is zero if the tape line is centred below the robot, between sensors 4 and 5. The value is the number of sensors away from the centre.		The line position is zero if the tape line is centred below the robot, between sensors 4 and 5. The value is the number of sensors away from the centre. The red line position measurement is about -0.6, and the blue is about +0.7.

	For every update of the line sensor data, a new turn rate is calculated and published on the MQTT server, which controls the wheels.		For every update of the line sensor data, a new turn rate is calculated and published on the MQTT server, which controls the wheels.