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Forum Index : Microcontroller and PC projects : Audio Oscilloscope using CMM2 ADC.
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KeepIS Guru  Joined: 13/10/2014 Location: AustraliaPosts: 1955 |
I've added a simple Waveform Generator to the CRO using the onboard PWM and DAC. Just makes it easy to quickly setup some simple wave forms. For displaying alternating waveforms from the DAC or other source, simply connect two 18k resistors to the input pin 7, one resistor connects to ground, the other connects to 3.3v, couple the input with a capacitor, value depends on input frequency but really for the purpose of playing around, anything from 100nf to 10uf would do. NOTE: Observe the 3.3v input limit on the analogue inputs. AudioCRO.ZIP  Edited 2020-08-01 14:22 by KeepIS NANO Inverter: Full download - Only Hex Ver 8.1Ks |
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hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 734 |
Is there avantage to PWM over PLAY SOUND ? my site |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1955 |
PWM is exactly that, pulse width modulation, a series of pulses at X frequency and of varying duty cycle as a % of the whole. Play sound uses the DAC and has implemented code to produce 5 basic waveforms. Other complex waveforms can be created using the sound DAC. The focus of this Audio CRO was on using the standard CMM2 functions and procedures. Play Sound is limited to 20KHz where as the PWM interface is up to 24MHz. . Edited 2020-08-02 08:55 by KeepIS NANO Inverter: Full download - Only Hex Ver 8.1Ks |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 734 |
I would like to do a crude ' real time ' oscilloscope using my ( still in the mail ) CMM2 .... Is that anywhere near realizable using an ADC pin ? Seems perhaps I would need an external ' flash ' ADC ? 50 kHz would be enough BW . Thank You ... my site |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1955 |
The requirements of a ADC with respect "accurate" waveform capture with increasing frequency is for another thread, however in simple terms, the ADC in the CMM2 will display a 50kHZ waveform, FFT transformation of the sample will show the correct frequency past 100kHZ. How you process and visualize the sample data is up to you. Edited 2020-08-02 13:18 by KeepIS NANO Inverter: Full download - Only Hex Ver 8.1Ks |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 734 |
Please forgive my ignorance . O.K.....It will display 50 kHz BUT Can it capture the waveform ( more or less ) realtime . I . E ..... Emulate the below ( but LEDS replaced by pixels .. my site |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1955 |
You are better of starting a separate thread on this as this will only confuse any new users wanting to just play with the CMM2 and the existing hardware. NANO Inverter: Full download - Only Hex Ver 8.1Ks |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1955 |
Just to answer that last question, YES it can capture in real time. NANO Inverter: Full download - Only Hex Ver 8.1Ks |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 734 |
Thank You ! So something like : ( way simplified ) DO CLS FOR x = 0 TO 255 y = READ ADC PIXEL x , y NEXT x LOOP Should work ? my site |
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