RS-232 Serial Port

[jhill0914]

I opened up the inspection checklist this morning and found the following entry:

Custom Circuits, Sensors and Additional Electronics - may not connect to the cRIO’s serial or Ethernet 2 ports (except in compliance with R69), ...

We have an embedded computer that feeds data to the cRio over the serial port, a setup we've used in the past without violating inspection rules. R69 only talks about the CAN bus, so according to the checklist we cannot connect to the RS-232 port. However, R72 lists the DB-9 RS-232 port as one of the valid connections for a custom circuit. I don't see anything else in the game manual that prohibits use of the serial port, and R72 seems to allow it, so is this just an error on the checklist?

[Jon Stratis]

The full text of the rules in question:

R69

If CAN-bus communication is used, the CAN-bus must be connected to the cRIO through either the Ethernet network connected to Port 1, Port 2, or the DB-9 RS-232 port connection.

Ethernet-to-CAN bridges or RS-232-to-CAN bridges (including the “black” Jaguars) may be used to connect the CAN-bus to the cRIO.
Additional switches, sensor modules, custom circuits, third-party modules, etc. may also be placed on the CAN-bus.
No device that interferes with, alters, or blocks communications between the cRIO and the Jaguars will be permitted (tunneling packets for the purposes of passing them through an Ethernet-to-CAN bridge is acceptable as the commands are not altered).


R72

All outputs from sensors, custom circuits and additional electronics shall connect to only the following:

other custom circuits,
additional COTS electronics,
input ports on the Digital Sidecar,
input ports on the Analog Breakout Board,
the RS-232 port on the cRIO,
the Ethernet network connected to either Port 1 or Port 2 of the cRIO,
the CAN-bus if and only if all Jaguar motor controllers on the CAN-bus are wired in full compliance with R68 and R69, or
the sensor inputs on the Jaguar motor controller.

Remember, the only official source of clarification is the Q&A, so ask there! However, my personal interpretation of this rule is that connecting other items to the serial port on the cRio is permitted so long as it doesn't interfere with CAN communication with the Jaguars. If you aren't using CAN, I don't think there's nothing to worry about... if you are, expect to have to prove to the inspector how the communication and control pathways work (we don't want the embedded computer talking directly to the Jaguars).

[jhill0914]

Thank you, Jon. That is how I interpreted the rules as well. My concern is that the way the inspection checklist reads it sounds like the only valid use for the serial port is for CAN bus communications per R69. While the rules seem to allow the basic connection to the serial port, I'm concerned that an inspector will look at that item on the checklist and reject our bot. We used the serial port last year to feed data in a similar way, and I think I recall having a similar issue with the checklist text. I went to the Q&A and registered, but under Team Questions it tells me my request is in a pending state and doesn't let me ask a question. If I can get authorization, I will ask on the Q&A.

[Joe Ross]

Originally Posted by jhill0914

I went to the Q&A and registered, but under Team Questions it tells me my request is in a pending state and doesn't let me ask a question. If I can get authorization, I will ask on the Q&A.

You won't be able to ask a question with your account (you can only follow questions). Your team's main contact needs to give you the account information for your team's account (available in TIMs).