Audio hardware

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Contents

Microphone

Sound Codec

The Hardware specification page says the Audio Codec is an Analog Devices AD1888, AC97-compatible audio codec.

The paper - 'The One Laptop per Child (OLPC) Audio Subystem' by Jaya (Alsa) provides useful information on the audio subsystem. The link is - The OLPC Audio Subsystem --Arjunsarwal

Microphone Sensor Input

The microphone input can be used to measure voltage or (using the Microphone bias voltage) resistance. This should enable us to use this as a form of sensor input with the audio analog to digital converter converting the sensor signal to a signal that can be displayed on the screen or logged by the computer. More info is required on the use of the codec in this mode.

  • max voltage that can be withstood safely by the mic input
  • Voltage corresponding to AD converter full scale.
  • Bias voltage output (open circuit)
  • Bias voltage output (short circuit)
  • Frequency range of mic input
  • anything else?

Uses of making measurement using the analog input port on the laptop

This section is useful for compiling a list of important and interesting uses for sampling analog input voltages using the analog input port of the laptop.It would also help in determining the end requirements of voltage range that would be required to be supported int he laptop at input.


Uses and their electrical requirements (Voltage range, bandwidth, Bias)

1. Checking the voltage of an AA/AAA/C/D type cells- Should be able to sample DC in the range 0-1.5V

2. Checking the voltage of a PP3(9V) type cell - Should be able to sample DC in the range 0-9V

3. Checking the voltage of a car battery - Should be able to sample DC in the range 0-15V

4. Interfacing an LDR/photo voltaic cell/Temperature sensor - Bias voltage required . Voltage range =

5. Robotics applications - The interface that is usually provided with commercial modules such as distance ranging modules is a 0-5V digital output. If the output voltage interface is RS232 type then voltage sampling requirements extend upto -12V - +12V. But then the XO has a serial port ? (Yes, but the connector is not exposed. --Walter 20:58, 24 June 2007 (EDT))

--Arjunsarwal

--dlarue 07:02, 15 January 2008 (PST)

Microphone data input

The microphone input jack can double as a dataport for some class of devices (when supporting a "DC-coupled" input mode), but a more general-purpose USB analog to digital device would be a great peripheral for the laptop. --Walter

Old thoughts

A built in Microphone would be usefully if dirt and echo/feedback could be controlled. If you have a microphone and speakers included with these laptops then then if you include a small piece of software they can be used as telephones or walkie talkies -- like an instant message local channel that is as easy to use as a CB radio. If the hardware looked like a radio, the operator could use it before they learned how to use the computer.

These are ideas related to both audio input and output. Please review the hardware specification to see what is already included. Some audio-related ideas are also dealt with in the Radio and Broadcast page.

Librivox

Human-read audiobooks for children as well as literature are going to be included in the OLCP project via content packs. A recurring idea I've seen crop up a few times is that of children recording their own audiobooks in return. What is the final quality of the built-in microphone?

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