Hi, can I connect the serial ground to the power ground leading to the TReX chip?


Yes, all of the grounds are connected internally.

- Ben

Does that mean I only need to connect one of the grounds on each chip? Not both?

It somewhat depends on your application. If you are using long cables that introduce significant impedance, you might run into some issues by making all of your ground connections in the same place. If you’re dealing with short cables of negligible impedance, you can make all of your connections to the the power input’s ground. Note that it does not work the other way; you cannot connect your battery’s ground only to a ground point somewhere else on the board because then all of the current pulled by the motors would be channeled through traces that are not meant to handle that amount of current.

Does this answer your question?

- Ben

Yes. So over an approximately 50 foot cable would I need to ground both?

Actually, grounding both through two very long cables could potentially create a high-current path to ground through traces that aren’t meant to handle high currents, so I would recommend against this. In general, using a 50’ tether will introduce a number of problems. For example, your motor voltage and serial voltage will experience significant voltage drops, and noise on the lines will be greatly amplified. If you need a long tether, I think you should run three wires to the TReX: serial signal, ground, and power. Make the ground wire as thick as possible to keep the impedance down, and connect your serial’s ground to your power source’s ground somewhere close to the battery.

- Ben

Ok, thanks a lot.