TMS320F280039C: passing a variable to DEVICE_DELAY_US() takes much longer time

Wayne Huang

Part Number: TMS320F280039C

Dear champs,

I am asking this for our customer.

The user has the same problem like

When I write DEVICE_DELAY_US(100), the timing is correct.

When I define any type of variable UINT16_t, float, long double and call DEVICE_DELAY_US(variable) the timing is wrong.

Looking at it

#define DEVICE_DELAY_US(x) SysCtl_delay(((((long double)(x)) / (1000000.0L / \
(long double)DEVICE_SYSCLK_FREQ)) - 9.0L) / 5.0L)

So, shouldn't whatever data type I input be converted to long double?

The timing always goes to ~2.4x 100 when I type to use any data type as input.

But it's not clear what the solution is in that post.

Do you have any suggestion if the user wants to use variable as a delay during runtime?

That is, the user just wants to delay 2.5us, 4 us, 6 us, like that during run time.

But these delay time are variables.

Can they use DEVICE_DELAY_US(var)?

Any suggestion here?

0 Aswin P over 2 years ago

Hi Wayne,

we can use the DEVICE_DELAY_US(var) function to provide delay as a variable.

Please go through the i2c_ex4_eeprom_polling example in c2000ware-release\driverlib\f28003x\examples\i2c folder for reference.

In the particular example we are passing variable value.

uint16_t WriteCycleTime_in_us; // target write cycle time. Depends on target.

WriteCycleTime_in_us = 6000;

DEVICE_DELAY_US(WriteCycleTime_in_us);

Please make sure the value passed as argument is the number of microseconds to delay.

Thanks

Aswin

C2000 microcontrollers forum