bug: backlight level 1 and 2 do not turn on backlight

[prokrypt]

known issue when pwm frequency is set too high. perhaps something can be adjusted to put the brightness scale back to normal.

[armel]

I know, it's not perfect, but it will be hard to fix.

The choice is as follows:

• low frequency for PWM = noise under modulation, but there is a visible diff between backlight levels 1 and 2
• high frequency for PWM = no noise under modulation, but there is no visible diff between backlight levels 1 and 2

The maximum frequency with a visible diff between backlight level 1 and 2 is around 7 kHz... But this frequency is audible (if your young...)

My choice is quickly made.

[prokrypt]

Random idea: how about increasing the pwm frequency only when transmitting?
Also, have you tested other frequencies? 12kHz-18kHz might not be very audible over radio tx. 25kHz seems a bit overkill to me.

[zardoz99]

Would this not cause a visual problem if you were running at a low number in the brightness scale. When you transmitted, it would make the display dim and you might be led to believe that there was a battery problem. It might be confusing for users. ---------------------------------------- *From: *prokrypt ***@***.***> *To: *armel/uv-k5-firmware-custom ***@***.***> *CC: *Subscribed ***@***.***> *Date: *Jun 13, 2024 11:46:09 p.m. *Subject: *Re: [armel/uv-k5-firmware-custom] bug: backlight level 1 and 2 do not turn on backlight (Issue #131)

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Random idea: how about increasing the pwm frequency only when transmitting? Also, have you tested other frequencies? 12kHz-18kHz might not be very audible over radio tx. 25kHz seems a bit overkill to me. — Reply to this email directly, view it on GitHub[#131 (comment)], or unsubscribe[https://github.com/notifications/unsubscribe-auth/AAQADJZLOTDFMPYND6UHHWLZHJRP5AVCNFSM6AAAAABJJOZSLWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDCNRXGE2TKNZVGU]. You are receiving this because you are subscribed to this thread. [Tracking image][https://github.com/notifications/beacon/AAQADJ5OE7EWUKKF5P4KANLZHJRP5A5CNFSM6AAAAABJJOZSLWWGG33NNVSW45C7OR4XAZNMJFZXG5LFINXW23LFNZ2KUY3PNVWWK3TUL5UWJTUBFQWCW.gif]

[armel]

Agreed with @zardoz99

Note that the human audible spectrum extends from 20 Hz to 20 kHz.
As I said, if the PWM frequency is above 7 kHz, there's no visible difference between backlight levels 1 and 2.
PWM frequency needs to be under 7kHz so... plain in human range.

Armel F4HWN.

[prokrypt]

As of right now, there is no difference between levels 0, 1, and 2... I'm not sure if that is a hardware thing though as I have a KSUN UV60D. I might have some experimentation with it a little later on.

[prokrypt]

I just did a simple test on UHF with a few different pwm values and an rtlsdr dongle and there was no difference in the squeal.
I'm not sure if the frequency is right as I haven't calibrated my SDR, but it seems there are two tones, one at ~3.75k and one at ~7.5k. What is clear though is that they remain relatively unchanged among different pwm values.

[prokrypt]

And while I'm at it, I decided to test another uv60d with LOSEHU's firmware (1000Hz backlight pwm), and some cheap "frs" radio I had nearby.

[armel]

Fixed in next release.