Sensors - Answers

[Billie Jean]

Answers to questions about Sensors

[Pierluigi Collina]

Subject: 3rd Party Quadrature Encoders

Question: May we connect 3rd party quadrature encoders to the encoder ports on the REV Hub / MR Core Motor Controller?

Answer: There is nothing in the rules that prohibits the use of 3rd party encoders with any of the motor controller inputs. Be aware that the PID control functionality depends on the characteristics of the encoders. It is possible that detailed configuration may be necessary.

[Pierluigi Collina]

Subject: Pixy/Pixy2

Question: Are the Pixy / Pixy2 sensors legal for this season as they were last year?

Answer: Yes. As long as they remain non-user programmable.

[Pierluigi Collina]

Subject: Intelligent Sensors & User Programmable Devices re: Pixy/Pixy2

Question: Can the GDC please clarify the ruling that the Pixy/Pix2 are allowed "As long as they remain non-user programmable"?

• <RE11> makes no mention that sensors cannot be user-programmable
• Assuming the above was an accidental omission, that makes the Pixy/Pixy2 totally useless, since they must be programmed through PixyMon in order to be useful.
• If PixyMon is simply counted as an exception to "programming" it, then does that mean that we cannot use the user-created FTC firmware recommended by the manufacturer on the FIRST Robotics support page which enables better compatibility with the MR CDIM / REV Expansion Hub?

Answer:

• <RE17> disallows "other electronics" and provides as a partial list of examples a series of user programmable devices. Intelligent sensors fall into this same category if they include user programming capability.
• PixyMon is a configuration tool, not a programming tool and is allowed to be used to configure the Pixy/Pixy2 modules.
• Loading user-modified or third-party firmware onto any module would be a disallowed modification of the module (<RE15>)

[Pierluigi Collina]

Subject: Optical Limit Switches as Sensors

Just Checking if the following sensors is legal, they do not have focused light, they are just IR senders and receivers
Opto Optical Endstop End Stop - They use a TAG to break the light to the receiver

Example Part https://www.ebay.com/itm/3Pcs-Opto-O...53.m2749.l2649

Answer: Yes. These are examples of allowed sensors

[Pierluigi Collina]

Subject: Configuration of UVC Camera from Robot Controller

My team was considering using a USB camera for our robot as allowed in <RE13>; however, the camera we want to use does not initialize in a UVC-compatible mode. It starts up in a USB "boot mode", and you have to load manufacturer-provided firmware, after which it re-enumerates as a USB UVC camera (actually two of them, as the device has two cameras). This firmware cannot be modified or programmed by us, and it acts as a normal camera after the initialization. If we wrote code to perform the initialization from the robot controller, would this camera still be considered legal?

Answer: Yes.

[Pierluigi Collina]

Subject: USB Sensor

Question: Our team had the idea to use the optical sensor of a mouse as a sensor in our robot in order to track our position. Is plugging a mouse into our USB hub and using the data from it in our program legal?

Answer: No. <RE11> limits sensors to being plugged into either the MR Core Device Interface or the REV Expansion Hub

[Pierluigi Collina]

Subject: I2C Multiplexers

In a previous year, a custom PCB for interconnecting multiple I2C sensors with a multiplexer was ruled legal ( https://ftcforum.usfirst.org/forum/f...-answer-thread ).

Q1) Is this still legal?
Q2) Would it be legal if we integrated a level shifter onto the circuit board? (rather than requiring an external REV level shifter)
Q3) Would it be legal if we added transistors that connected to a digital port on the REV Expansion Hub and the VCC of the sensors, to allow us to turn the sensors on and off? All of the power would still originate from the Expansion Hub, we would just have the transistors to interrupt the power to a sensor if we wished to turn it off.

Thanks!

Answer 1: Simple I2C Multiplexor are allowed per <RE11>.f
Answer 2: No - <RE17>
Answer 3: No - <RE17>

[Pierluigi Collina]

Subject: Controlling Sensor Power

My team has multiple Modern Robotics Range Sensors on our robot, and we're worried about interference between them; so, we would like to be able to turn on and off the sensors in our code, letting us disable sensors we don't need to use. We've checked, and there's no control over the ranging of the sensors: they start continuously ranging as soon as they receive power, meaning that we cannot stop them apart from turning off the power.

Q1) Is programmatically controlling the +5 volt or +3.3 volt power going to a sensor legal, as long as the power originates from the REV Expansion Hub or Core Device Interface Module?
Q2) Would we be permitted to use an I2C I/O expander to do this? (assuming we found one with a current output capability that exceeds the sensor's requirement)
Q3) Would we be permitted to use the REV Expansion Hub or the Core Device Interface Module's digital output ports to do this? (again assuming that the devices could supply enough current for the sensors)

Thanks!

Answer 1: If the REV Expansion hub supports enabling/disabling power to the sensors this would be allowed.
Answer 2: A simple I2C Mux is allowed per RE11.f ... anything more complex would not be allowed per RE17
Answer 3: If the sensor supports an additional control signal that enables/disables the sensor, this would be allowed

[Pierluigi Collina]

Subject: Sharp Distance Sensor

Q: Is the Sharp GP2Y0D805Z0F Digital Distance Sensor permitted? A detailed description can be found here: https://www.adafruit.com/product/3025

A: There is nothing in the rules that prohibits the use of this sensor