Matrix user forums

how can i generate delay for nano seconds in flowcode?

other members please correct me if im wrong, i dont think you can because of the clock speed limitations, at 32 Mhz clock it takes 1 microsecond to turn a output on and off, at 4Mhz it takes 8 microseconds thats straight time without any delays

brandonb wrote:other members please correct me if im wrong, i dont think you can because of the clock speed limitations, at 32 Mhz clock it takes 1 microsecond to turn a output on and off, at 4Mhz it takes 8 microseconds thats straight time without any delays

Yep, Brandon are right, but you can have 1 instruction cycle delay with asm nop command (thats 100ns@40MHz chip clock)...

i am trying to drive a chopper transformer for switching supply. what do u advice?

Hello,

the dsPIC 33 family can run up to 40MIPs so one 16-bit instruction every 25 nano seconds.

What kind of resolution are you looking for?

benj all i want is to drive a soft ferrite transformer, or u can say 12vto48v dc-dc converter for charging batteries from solar energy.
i am confused about the frequency on which chopper works.

Hi.

Isn't that easier done at hardware pwm?
At dsPic30f you can get 300KHz pwm at 1% resolution ( I am not an expert, but is there any reason to use very high switching frequency, it just rises the switching loss)...

Mika

i guess i need only 2 - 20 khz switching. how can i do that by pic16 devices?
when i put a delay for micro seconds, on scope it shows time for milliseconds....whats going wrong there?

regards.

did you set up the clock frequency in (build,project options) the same as your osccon register c block (if applicable)

Hello Greentech,

Use the 1 second flasher test to confirm you have everything setup correctly.

eg

while(1)
{
output 1 to LED pin
delay 1s
output 0 to LED pin
delay 1s
}

When the delays on the hardware match 1 second you have the Flowcode clock speed and configuration settings setup correctly for your hardware.

Checked it benj, all woking fine except for the pulse delay is in milliseconds when i hook it to scope. I am trying to get 2 pwms 180 degrees out of phase. how can i invert the pwm?

greentech wrote:Checked it benj, all woking fine except for the pulse delay is in milliseconds when i hook it to scope. I am trying to get 2 pwms 180 degrees out of phase. how can i invert the pwm?

In hardware pwm you need eccp module and set the register via c-code, if you want full or half bridge configuration, some 16f chips have the eccp module, then you can set two pwm:s at the 180 degrees phase shift (or actually one pwm, which drives two pins), and the dead band delay is adjustable too, but at least at version 4 flowcode doesn't support that.. But it's the "sure" way, that way there is hw logic to prevent switches opening at the same time...

Mika

greentech wrote:I am trying to get 2 pwms 180 degrees out of phase. how can i invert the pwm?

Hi greentech,
Same question was asked on a different thread so I posted a solution here:
http://www.matrixmultimedia.com/mmforum ... 701#p26295

The only issue will be a slight delay at the higher speed end.

Mika coved Other options which I totally agree with.

Although Flowcode does not support half bridge using ECCP, I would guess this could be achievable using C code and would be the best method if not using external components.

Another method to consider, is connect the PWM output to a spare interrupt on change input pin, then within IOC macro an output pin can be = NOT IOC input.

Martin