Hi,
I am trying to understand a circuit of the open-source oscilloscope project because I want to build something similar, but there is one part which I don't get exactly.
This is the schematics: http://essentialscrap.com/dsoquad/DS203V2.png
So after the second multiplexer in the input section there is "final" operational amplifier, from which output goes to multiplexer and then to ADC. What I don't understand is the circuit which is connected to the positive input of that operational amplifier, and especially why is there connection (red V1 mark) to the processor (I looked up the input pin of the processor where this V1 is applied and it is ADC or standard I/O).
Does anybody have idea what is the purpose of this output ? Isn't it dangerous for the processor if higher negative voltage is applied to oscilloscope input?
Another question I have is also why is output of CHa connected to mux of CHb and vice versa?
Thanks for replies, Joost
I am trying to understand a circuit of the open-source oscilloscope project because I want to build something similar, but there is one part which I don't get exactly.
This is the schematics: http://essentialscrap.com/dsoquad/DS203V2.png
So after the second multiplexer in the input section there is "final" operational amplifier, from which output goes to multiplexer and then to ADC. What I don't understand is the circuit which is connected to the positive input of that operational amplifier, and especially why is there connection (red V1 mark) to the processor (I looked up the input pin of the processor where this V1 is applied and it is ADC or standard I/O).
Does anybody have idea what is the purpose of this output ? Isn't it dangerous for the processor if higher negative voltage is applied to oscilloscope input?
Another question I have is also why is output of CHa connected to mux of CHb and vice versa?
Thanks for replies, Joost