writeDigitalPin question in matlab

Hi all,

I connected Rapberry PI to Fischertechnik robot model and I have a question about it -

I know that there is the command:

writeDigitalPin(r, 23, 1);

But, the robot have 2 opposite directions that it can be moved to each one of the motors...

So, how can I write in the code which one of the 2 directions I want?

Thank you!!

Answer 1

[Walter Roberson]

You cannot. writeDigitalPin() does not support tri-state pins (left, off, right); it only supports binary (off, on) .

Systems with motors often use one of several systems:

• quadrature encoding; https://cdn.sparkfun.com/datasheets/Robotics/How%20to%20use%20a%20quadrature%20encoder.pdf
• separate pins for each direction --- this is less common and leads to questions about what should happen if both pins are active at the same time
• analog signal in which negative indicates opposite direction
• two bits grouped together that are together interpreted as a binary value that indicates direction number; this leads to questions about what to do with the 4th value. Sometimes two stop states are defined and gray encoding is used: 00 -> stop; 01 -> right; 11 -> stop; 10 -> left

[Sapir Zurist]

And do you know how can I controlled the speed of the robot by moving its motor?

[Image Analyst]

I doubt he'd know that. I think you'd have to consult the manual for your motor (which we don't have).

[Walter Roberson]

See the description from line 226 at https://github.com/CodaFi/FTKit/blob/master/fischertechnik/fischertechnik/ftapi.h

Each motor has two controlling outputs 0 to 7 for speed. One output for each direction. For reverse set the first output to 0 and a speed for the second output.