Arduino based DVM for synth/audio--analog TFT meter?

[cslammy]

Hey folks--trying to create this and I am stuck on the VU meter itself....getting the Y axis to work.

For full details about what I am stuck on, Please take a look at my blog to see what I am stuck on if you have time. The problem is a bit complex and is driving me bonkers.


http://audiodiwhy.blogspot.com/2018/06/synth-dvm-part-iii-vu-blues.html

In a nutshell, I am using Adafruit GFX library with a nano. This library is super easy to use but as far as I can tell it can't create diagonal lines of a consistent length without some hacking. And that's what I need....

So meter needle length isn't correct--Y is a constant value and shouldn't be--in the real world an analog meter needle is always the same length!

Can anyone please suggest a good way to fix this? I am a decent coder for Arduino but not great having just started using these handy devices a couple of months ago. Willing to learn! Thanks in advance.

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[Grumble]

The fastest way to accomplish this is to make an array with the x and y coordinates for all voltage inputs. Similar to a lookup table for waveforms.
That way no (s l o w ) calculations with sin/cos are necessary.

[cslammy]

[cslammy]

Grumble, good advice, the array did the trick!!!

Thanks! I'll post what I ended up using on my blog.