TMS320F28069M: velocity problem gMotorVars.MaxVel_krpm

Jakub Jurica

Part Number: TMS320F28069M

hello,

My application read joystick and send velocity via CAN interface. Project is modified from labs13e. Max speed of motor is 1500RPM. When I send velocity from range 0-1500 and use

gMotorVars.MaxVel_krpm = _IQ((float)speed/1000)

it seems everything works good.

But for example when application use velocity range from 0-20000(example) I need convert to max velocity 1500. So I do

float vel = (float)speed/GEARBOX;

gMotorVars.MaxVel_krpm = _IQ((float)vel)

sometimes motor run with double speed. In expressions window I see that gMotorVars.Speed_krpm show 2x bigger number then gMotorVars.MaxVel_krpm.

When I try convert with this(without cast float) so no decimal number, it is work.

float vel = speed/GEARBOX;

over 8 years ago

0 Sean Bigley over 8 years ago

TI__Genius 17175 points

What is the possible range of vel? Are you overflowing the value of IQ24 (-128<->127.99999)?

Sean

0 Jakub Jurica over 8 years ago in reply to Sean Bigley

Prodigy 120 points

It should not overflow. I check it in graph.

test:

float fvel;

void run(int16_t velocity)

{

fvel = (float)velocity/6000;

gMotorVars.MaxVel_krpm = _IQ((float)fvel);

}

velocity is from 0 to 8000

second case when working

fvel = (float)velocity/1000;

velocity is from 0 to 1500

0 Sean Bigley over 8 years ago in reply to Jakub Jurica

TI__Genius 17175 points

Does the compiler throw an error if you do not explicitly cast fvel to float type in this call:

gMotorVars.MaxVel_krpm = _IQ((float)fvel);

If not, can you try passing just fvel?

Sean

0 Jakub Jurica over 8 years ago in reply to Sean Bigley

Prodigy 120 points

There is no error in compiler. It looks like it will be a mistake in the debugger. I came in the morning to the work and remove float from_IQ((float)fvel). It worked.
But about one hour later the same issue again. When I terminated debugger, the motor velocity was ok.
I tried disconnect debugger, close CCS, everything power off but this did not help.

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TMS320F28069M: velocity problem gMotorVars.MaxVel_krpm