PWM duty setting with 8bit number

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

PWM duty cycle bug? v4.099

Ttelmah · Guest

It wil do.

It is in the manual.......
It has also been covered here many times.

The set_pwm_duty function, has two different modes of operation, according to whether the value it receives, is an 8bit value, or a 16bit value. If you pass an 8bit value, it only accesses the top 8bits of the 10 bit register, saving the overhead of masking off the two low bits, and putting these into the separate locations. Pass a 16bit value, and the extra work is done. Makes it possible for _you_ to decide if you need to perform a 10bit access, or only the 8bit access.

When using a constant, you need to tell the compiler _explicitly_, that you want it to treat the value as a 16bit number, if you want the 16bit operation, if the value is below 256:

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

Thanks, the "8-bit value may be used if the most significant bits are not required" on first read I though that the "required" referred to me and not the hardware :-)
Thanks for the L thing, you learn something every day. I am now changing my set_pwmx_duty(0) to set_pwmx_duty(0L) to be sure the top two bits are 0.