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sdsteam
60 Posts |
 Posted - 27 Jan 2004 : 10:50:24
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Our application requires that we feed a sinewave input into the Mic inputs of Bitsy-X to be Mixed with Some other Wav files within the Codec of Bitsy-X.
We tried this in a Bitsy-X development system(Bitsy-X + Companion Board) and it worked fine.
If we put the same Bitsy-x into our custom Hardware, We are not able to control the volume of the sine wave mixed in Codec. We were able to do this with the Bitsy-X development system.
Please highlight any special feature that is present in your companion Board that could enable this in HW. Please provide us a solution ASAP |
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akidder
1519 Posts |
Posted - 30 Jan 2004 : 10:50:08
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Thanks for your post. Perhaps you could take a look at the differences between your audio circuits and the schematics of the Bitsy personality board. What version of the BitsyX and personality board are you using? Are you using the speaker outputs or the headphone outputs? How are your microphone inputs connected? Have you compared the signal levels each of the configurations by measuring with an oscilloscope?
This is the kind of issue that is probably best resolved off-line, as it involves hardware that we didn't design. Once we figure it out, I'll be glad to fill in other readers on the resolution of the issue.
You can call us or send us a message at support.us@eurotech.com. |
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sdsteam
60 Posts |
Posted - 14 Feb 2004 : 00:10:36
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| We found that the audio was indeed getting controlled, but when mixed with the wav files, the change in volume of MIC input was not very prominent. Can this be made more prominent by increasing the amplitude of the signal fed into the MIC input. What is the maximum amplitude that can be fed into the MIC input? |
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akidder
1519 Posts |
Posted - 16 Feb 2004 : 10:41:10
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Thanks for the information you provided. Do I understand correctly that you have already tried out the standard linux OS ioctls for the MIC and PCM volume? Those volume controls can mix the mic and digital signals for most applications.
Controlling the Mixer
If the standard controls don't give you the amplification or flexibility you need, you may need to control the AC97 codec audio mixer directly. There are a number of mixing and routing options available, at least one of which may give you the functionality you need. Take a look at all the ways the codec signals can mix!
Source: Crystal CS4202 codec data sheet, May 2002 (PDF)
MIC vs. LINE_IN
As you'll see in the audio specifications section of the BitsyX Users Manual (section 6.2.9, topic 884), you can use either the MIC or the Line_In inputs for your incoming audio stream. The MIC input channels have the disadvantage of being mono (you can select only one at a time), but have a strong advantage of supplying significant gain stages before the mixer. See the codec manual for details.
For Further Help
If you continue to have trouble with this, please contact us (link above) with at least the following details:
- amplitude of the incoming signal
- details about and/or a sample of the PCM signal you're mixing with the input signal
- which input you are using for the signal (MIC or Line_In)
- small application or code sample that indicates the settings you have tried
Let us know how we can help!
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