I am looking into the possibility of using a VEX controller in autonomous mode, possibly as a sensor/control front-end processor to a laptop for robotics. It would be helpful if there were some basic information about the function of the Master Processor and some details for the interaction between this and the User Processor. In addition to assisiting in understanding the programming constraints of the User Processor, it would help in evaluating the usefulness of writing code for the Master Processor, which I understand can also be downloaded.
The Master processor handles all the communications with the transmitter. It also oversees what the User processor is doing. The Master can hold the User in a reset state if a violation is detected. The Master code is proprietary and can not be released. You can download Master code (a bin file), but you can not make changes to it.
I am trying to understand the “big picture” of the VEX controller. I am experienced in C programming and have helped the local high school team with their FIRST robot. I understand a little bit about the presence of a master and user processor. But how do these play together? (I am embarking on the path of using MPLAB and the IFI loader so I can write my own C code.) One specific example: I am trying to understand the C code portion that lets me pick user or master control of the PWMs. Why would I want to change these settings? What are the advantages of User versus Master? What information is available to help me decide User or Master? These are the questions I hope a “big picture” overview or flow diagram would solve.
We are working on more documents for Vex. Until then you can view the documents we developed for another control system which is very similar to Vex at http://www.ifirobotics.com/rc.shtml#Programming Look at the Reference Guides on this page and on this page [http://www.ifirobotics.com/mini-rc-read-me.shtml It is always better to let the Master handle things. The User is for specific cases that may be required when a specific type signal is required. The User is not protected from interrupts which can affect the PWM signal timing.](http://www.ifirobotics.com/mini-rc-read-me.shtml It is always better to let the Master handle things. The User is for specific cases that may be required when a specific type signal is required. The User is not protected from interrupts which can affect the PWM signal timing.)