There are multiple ports/connectors on the RM, what are they for?

1. Micro-USB on Intelligent Controller
2. USB-C on Intelligent Controller
3. 4-Pin on gimbal (CAN?)
4. Multiple connectors inside the controller module (CAN, UART, PWM, ...)

I'm guessing these are for firmware update and future 'expansions' ... but let's be a bit more specific.

"4-Pin on gimbal (CAN?)"
Yes, the top port covered by a rubber plug is a CAN Bus port. There's a black rectangle covering another port next to it. The black rectangle covers a white connector with five conductors.


The PWM ports on the Motion Controller can control servos or other things which can use a 50Hz PWM output. A 7.5% duty cycle corresponds to a 1500us pulse. 5% PWM output corresponds to 1000us pulse and 10% PWM setting corresponds to a 2000us pulse. This lets one control servos relatively easily from Scratch or Python.
There was once a note about the UART and SBUS ports on DJI's S1FAQ. The FAQ said these ports aren't supported and using them could void the warranty. I was very disappointed to see they weren't going to support the UART of SBUS ports. I hope they change their mind about this.
SBUS is a common RC protocol used with radio controlled airplanes and quadcopters. FrSky and other companies use SBUS to communicate with flight controllers.
A SBUS port would allow one to use common radio control transmitters as an input device for the robot.

Those ports are all for expansion and accessories. Unfortunately, how to access and use them is very poorly documented. The Scratch IDE provides one Block, under Chassis, to set the output of the PWM ports. The Block has a set of matching Python functions to do the same.

rhoude57 - YUL Posted at 10-1 12:37
Those ports are all for expansion and accessories. Unfortunately, how to access and use them is very poorly documented. The Scratch IDE provides one Block, under Chassis, to set the output of the PWM ports. The Block has a set of matching Python functions to do the same.

Yep. Based on the documentation, currently the PWM ports are the only ones that are supported at all. The other ports might eventually be enabled for programming or might never really be (that would be a shame).

Hey what if I want to connect to that open CAN bus connector on the gimbal?  Can someone link me to a cable I can cut to solder to my laser diodes?  I know it's got 5V and Gnd right there...

MarkusXL Posted at 10-2 09:37
Hey what if I want to connect to that open CAN bus connector on the gimbal?  Can someone link me to a cable I can cut to solder to my laser diodes?  I know it's got 5V and Gnd right there...

The pins are on a .1 inch spacing, so you could use jumpers with female headers.

Like this: https://www.sparkfun.com/products/8430

For two conductor scenarios I just put a bit of heat shrink around them to keep them together. That's how I hooked up servos to the PWM ports.

MarkusXL Posted at 10-2 09:37
Hey what if I want to connect to that open CAN bus connector on the gimbal?  Can someone link me to a cable I can cut to solder to my laser diodes?  I know it's got 5V and Gnd right there...

The CAN Bus does not have 5V. It has ground and battery voltage on the bottom two pins.

The pin labelled "3" is ground and pin "4" is ~12V (battery voltage).
The PWM/Servo connectors have a 5V connection. These connections should provide powerful enough current for small servos. I'd use these connections for low power 5V devices.

I'll add normal 0.1" connectors, like the ones gpvillamil linked to, also work with the CAN Bus ports.
Here's a photo of using these sorts of connectors on three of the four CAN Bus pins.

UART port can be used apparently:
https://robomaster-dev.readthedocs.io/en/latest/python/uart.html