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Posted byatmega1284p4 years ago
Connecting the Cobbler to a MCP3008. By Michael Sklar. Pi computer does not have a way to read analog inputs. It's a digital-only computer. Compare this to the Arduino, AVR or PIC microcontrollers that often have 6 or more analog inputs! Analog inputs are handy because many sensors are analog outputs, so we need a way to make the Pi analog. Digital and analog grounds get happily mixed everywhere. Even one digital ground pin (55) is directly connected to the paddle under the AVR which is internally connected to analog ground. Also, the crystal layout looks quite vulnerable in contrast to the AVR2005.
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I'm building a project that uses a D/A converter chip (Yamaha YM3012, 16-bit floating point stereo DAC for those interested) which requires not only the standard ground for the digital signals, but a separate analog ground for the audio output stage; I believe tying these pins to the standard ground is what is causing the extreme audio distortion I am experiencing, so I absolutely need to have a separate ground line.
I am working on a breadboard since I am still prototyping. Does anyone have any ideas how I can achieve a separate ground line? I'm just using a USB cable as the power supply at the moment, if that matters. Leaving the analog ground pins unconnected results in no audio output, so even that isn't an option for me.
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