Multi-Button CSM with Pic16LF722A

[richard]

Just curious as to why there isn't any reference to the PR2 register in the program, for setting up the PWM?

flicker is virtually invisible to the human eye for switching frequencies above 50 Hz, switching losses increase with frequency , other than that the frequency is irrelevant .
fine control of the pwm frequency is possible using pr2 at the expense of resolution . since the frequency is largely irrelevant why not have maximum resolution

If I wanted to increase the pwm frequency to 25Khz, I take it I would have to go to a higher oscillator frequency and use different prescaler values?

depends on required resolution, @4mHz 25kHz is possible with 1:1 prescale and pr2=39 , however maximum duty occurs @ pwm_duty_reg = 160 , ie pw range is 0 to 160 (instead of 0 to 1023 steps as before)

[Aussie Barry]

Hi All,

Has anyone had any experience with a 2 channel CSM slide switch?
I would like to implement a slide switch rather than an up / down button arrangement to select the PWM output for a LED string.
In my case, the granularity is quite coarse - only eight steps of PWM selection.

Any input would be greatly appreciated.

Cheers
Barry

[RWright]

Hello,

Regarding the flicker, you know this and I know this, however, we are trying to match an existing product that is set at 25khz. It appears at lower frequencies
it is causing their power supply to make audible noise at the PWM frequency. And sure enough, at 1khz, at certain pwm levels, we can hear it in the power supply. I don't have to keep the oscillator at 4khz, but I assume making any changes to the main Oscillator will also affect the touch circuit, as well. I did see in the pwm section of the datasheet that the resolution drops depending on the oscillator frequency after I posted this. Thanks again!

[RWright]

Sorry for the repeated post.

[richard]

for barry

Has anyone had any experience with a 2 channel CSM slide switch?
I would like to implement a slide switch rather than an up / down button arrangement to select the PWM output for a LED string.
In my case, the granularity is quite coarse - only eight steps of PWM selection.

have now, seems to work nicely

slider as per http://ww1.microchip.com/downloads/e...tes/01250a.pdf
made on ds board the bottom side is unconnected, slider pad are 10mm*40mm the top is grounded
covered with sticky tape (durex for a sniker from the euro's)
see pic

[richard]

a slider design like this on single sided board is worth trying out,i think it would be more sensitive and the board could be painted to encourage the user to slide finger along the horizontal line. next time i'm doing some chemical etching I will make one [if I remember]

[Ioannis]

Is it necessary to have the ground line in the middle of the two channels? Won't this affect the operation.

Ioannis

[richard]

Is it necessary to have the ground line in the middle of the two channels? Won't this affect the operation.

according to this app note it is

http://ww1.microchip.com/downloads/e...tes/01250a.pdf

I have not tried without it , the other way is to use a chevron pattern which has no earth requirement
but uses more pins [several]

[Ioannis]

OK, yes. It is used toi isolate the two sensors between them.

Thanks,
Ioannis