After a lot of messing about with other stuff, Primus is now back on track and has the basic motion code written and installed. Movement within the maze is possible with steering off the walls to prevent collisions; fixed size moves and in-place turns are functioning; forward error detection and correction is working.
Well, it has taken a while but I have finally got the motion control properly underway. Code details will follow shortly. In the meantime, you can see the beast move on YouTube:
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The sensors are a critical part of a micromouse. Primus uses six infra-red reflective sensors. Here is code to test that they are working.Now that we have a nice display to show what the sensor reading are, we can get that module tested. Since the hardware is very simple, there is not a lot to go wrong. Yet somehow I had a dead sensor when I first tested the Primus prototype. It was a simple dry joint that would have been detected by more careful inspection of the board. (more…)
This is a fairly big jump. With the LEDs and buttons tested, it is time to add the main graphical display, made from a Nokia cellphone display. Also, there is the main system timer event.
The simple user IO is working, and it is time to add a system timer. This will generate an interrupt every millisecond. In the final mouse a lot of work will be done in here – processing buttons, driving the LEDs, reading sensors and calculating drive signals for the motors.While that may seem a lot in a millisecond, the dsPIC used in primus can execute about 16,000 instructions in that tme and we should only need a small proportion of that time. (more…)
After a bit more thought, there is now a new set of pin assignments for the Primus micromouse, along with a corresponding schematic.The problem with Primus was that it is not possible to generate two independant pulse trains from the PWM generators. All the PWM channels have to share a common time base.The Output Compare peripherals on the dsPIC30F4011 can generate up to two independant pulse trains in hardware but one of the time bases must come from Timer 2 which is needed for counting steps sent to the motors. One of the fundamental design decisions on Primus is to drive the two steppers at high speeds without any interrupt service routine soaking up processor cycles.It seems that one motor will have to be driven from an OC channel and the other from a PWM channel. (more…)
It seems I made a bit of a mistake in how I thought the dsPIC could drive its PWM module. Consequently, there will have to be some changes.First, what can’t change is the need to use T1CK and T2CK as external inputs to count motor pulses. There are no other choices on the dsPIC30F4011 without using interrupts. Since I anticipate pulse rates of up to 100,000 Hz per wheel, life will be a lot easier not having to service that interrupt rate, even with a fast processor and a very efficient ISR. (more…)
The next stage in testing the Primus hardware is to make sure the buttons are working.Building on Primus 1, the button hardware is tested in the simplest possible way. Calling the readButton() function sets a number of exported variables indicating the button status.These are tested inside a loop in the…
Once the main board is assembled, it can be tested without waiting for the sensor or motor driver boards to be ready. In time honoured fashion, we start with a little program to flash the LEDs.With any new microcontroller project, it is a good idea to start with some simple code that will allow you to test your ability to create a project in the chosen development environment, compile the program, transfer it to the microcontroller and run it. While you are at it, you get to test the simplest part of the system hardware. (more…)
I finally have a primus mouse built and ready to test. All the bits are there and the processor runs up and can be programmed. Here are a few pictures to get you in the mood.By placing the components on three separate boards, each is relatively simple to build and…
The Primus micromouse will use the dsPIC30F4011 processor from microchip. It has plenty of power and resources for just about any micromouse and is relatively easy to get and use. Here is a list of the proposed functions for each processor pin on the controller board dsPIC30F4011 Pin Functions for…