I tried and abandoned a “pass through set-up”.
My initial solution used a “pass-through” set-up, where by a “man-in-the-middle” sat between the Pendant and the robot (pendant port). It could listen to messages the Pendant sent and inject it’s own.
Initially this seemed to work quite well. But once I started adding more processing that the messages had to go through (to track what was happening in the pendant messages), I found that the latency seemed to cause communications issues. Some routines (such as the homing routine) were very “chatty” (rapid back and forwards) and keeping up with this and parsing all the UART text seemed beyond what the ESP could handle (or at least beyond my rooky UART text parsing skills). For example the pendant continually asks the controller if it is about to stop moving when you hold down a movement key on the pendant, and issues a new movement when it is about to stop.
After frustration at not being able to get the pass-through solution scaled-out I desperately tried plugging in my solution to the computer port and to my surpsrise it worked quite well. The catch is that only one port can be used at a time and you can’t track Pendant commands. With the pass through you could use either the ESP or the pendant to control (rather than needing to switch).
