emul/pico-zxspectrum
emul/pico-zxspectrum
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analogue mix of AY and buzzer

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Phil 2022-06-12 06:59:10 +01:00
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8
README.md
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@ -80,6 +80,7 @@ zxspectrum/kiosk.txt
| GP14 | | 14 | 19 | | | TXC+ | Clock + |
| GP15 | | 15 | 20 | | | TXC- | Clock - |
| GP20 | | 20 | 26 | | | | PWM audio out |
| GP21 | | 21 | 27 | | | | Digital audio out |
![image](https://www.raspberrypi.org/documentation/microcontrollers/images/Pico-R3-SDK11-Pinout.svg "Pinout")
@ -88,8 +89,11 @@ zxspectrum/kiosk.txt
<img src="docs/pico_zxspectrum_prototype_1.jpg" height="200"/>
### Audio filter
It's a good idea to filter out high frequencies from the PWM audio output.
The following components were chosen as I found them in a draw... but it sounds ok.
High frequencies need to be filtered out of the PWM audio output and mixed with the Spectrum's digital audio.
![image](docs/audio_filter_mk2.png)
Designs that only have a single GPIO pin available can still have the audio mixed digitally.
![image](docs/circuit.png)

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docs/circuit.png → docs/audio_filter_mk1.png
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