MicroMite 3DOF Controller

Discovering the MicroMite Microcontroller by Geoff Graham (link: http://geoffg.net/micromite.html)
has given me the opportunity to write a short Basic program which can drive up to 3 wiper motors using 3 Pololu interfaces. This MicroMite is based on a 28 pins PIC32 microcontroller loaded with a Microsoft compatible Basic interpreter, below is a summary of all related informations and files required.

The MM is a very simple microprocessor and as most of the required features are pre loaded, programming in Basic is very easy. The PIC32 allows up to 5 PWM outputs, but a max of 3 can only be used as some pins terminals are required for the POTS input and LED display.
Best way to program the MM is to use the Windows editor MM-Edit which can be downloaded from http://www.c-com.com.au/MMedit.htm





The first PC Board V1.0 as shown above allows programming through the USB-SERIAL 6 pin input (jumper J1) with J2 and J2a bridged. The same USB-SERIAL jumper 1 can be used for the Game Data Input with jumper J2 and J2b bridged.
Programming will require the COM speed to be set at 38,400 Baud,8 Bits, No Parity, 1 Stop.

The revised PC Board V1.2 has 3 additional Jumpers. Aux J8 and Aux J9 which are connected to 2 unused pins on the MM (Pin 7 and Pin 14) these could be used to set the LCD module to display less numbers of DOF readings <line106> + <line107> or for 1 alternative input and output. The 3rd new Jumper J2c is an additional Game Input which allows connecting directly to a low cost RS232 interface.
The circuit already allows for high voltage level reduction by means of the D1 Diode and R2 Resistor, but the signal polarity needs to be inverted within the MM basic program and in this case the OPEN command on <line48> requires an additional ‘INV’erted option as shown below.




The use of the 2 ‘Pots Limiters’ values assist in working at the centre of the pots movement, thus covering for any possible 'overrun' past the 90° angle standard movements of the wiper motors. In any case, I would recommend opening the pots and flattening the pot arm stopper from the pots casing or cutting the plastic extension as this will prevent damaging them when testing for correct polarity connection to the wiper motors.



The SimEngine interface output used must be: A<Axis1><Axis2><Axis3>Z, the PIC32 waits for the ‘A’ input and then it reads the next 4 bits and if ‘Z‘ is there at the end, it executes the rest of the program with these new values.




Some of the “DIAGNOSTIC: …” lines can be activated (remove the {‘}) to display the game output values through MM-Edit by making use of both the USB and RS232 connections.




There is no need to use all 3 DOF modules, but if 1 or 2 only used, the SimTools interface outputs signal will still require the 3 axis values, alternatively the Basic program will need to be revised to read only what required <line62> to <line67>

Although the MM Basic program and PCB V1.0 has been made and fully tested as shown in the video below, the implementation of the latest PCB V1.2 has not been tested yet.



More informations regarding the actual chair unit can be found here:
http://www.xsimulator.net/community/marketplace/2dof-3dof-optional-descriptions.81/

Downloadable files:
Components list and prices
PCB Layout
PCB Silkscreen
PCB etching
Circuit Schematic
MM Basic program
(remove the additional .txt extension when loading the program into MM-Edit)

I strongly recommend to fully read all details provided by Geoff Graham on his web-site page and also to refer to additional related links:
http://geoffg.net/micromite.html
http://www.thebackshed.com/forum/Microcontrollers
http://www.c-com.com.au/MMedit.htm
http://micromite.org/
http://www.siliconchip.com.au/ (May 2014/June 2014/January 2015 issues)