LEGO

Description

The LEGO is not yet defined but is based on up to for DC motors controlled via the RPi's hardware PWM. The RPi interacts with H-bridges such as L293D instead of the classic relay board. Up to 8 pins are used 4 with the hardware PWM and 4 for the direction selection.

Network location

• Hostname: lego
• URL: http://lego.local
• URL for motor control: http://lego.local/motor

Workflows

• accelerate: Motor speed is increased by 20%. The speed can't go above 100%.
• decelerate: Motor speed is decreased by 20%. If the speed goes negative, the direction is reversed. The speed can't get lower than -100%.
• stop: Motor speed is set to 0%.
• full_forward: Motor speed is set to 100%
• full_backward: Motor speed is set to -100%. The direction is reversed.

Raspberry Pi pinout:

RPi Pin	RPi Name	Destination	Wire	Function
1	3V3	H bridge VCC	brown
6	Ground	H bridge Gnd	black
12	GPIO18	H bridge IN 1+	red	PWM motor 1
16	GPIO23	H bridge IN 1-	orange	DIR motor 1
32	GPIO12	H bridge IN 2+		PWM 2
	GPIO	H bridge IN 2-		DIR 2
33	GPIO13	H bridge IN 3+		PWM 3
	GPIO	H bridge IN 3-		DIR 3
35	GPIO19	H bridge IN 4+		PWM 4
	GPIO	H bridge IN 4-		DIR 4

TODO

• Expand implementation to four motors. Today, only PWM 1 and DIR1 are supported. PWM 1 pin mapping is hardcoded as well.
• Make the transitions of the motor speed smoother by changing the speed in 20% steps. Today, it can change from -100 to +100% which creates are large ruck.
• Accelerate the handover of speed changes. Today, the new speed is hander to the PWM control task which applies the new value every 100ms.
• Also, the speed changes are applied with a HTTP GET which requires a page to be returned. With a PUSH it might be quicker. Same as for the button toggles. This would require a custom control page for the motor controls like the system page. How about a slider for the speed? We need a generic route for setting the motor speed. DONE
• PWM frequency should be made a parameter.
• The speed step size (today 20%) should be made a parameter.