User`s guide

Intel
®
StrongARM
®
SA-1110 Microprocessor Development Board User’s Guide 4-31
Hardware Considerations
4.12.4 Microphone and Speaker
The SA-1110 Development Board includes two built in electret type microphones as well as a mini
speaker.
Two microphones are required to provide optimal sound capture. One microphone is used during
dictation when the SA-1110 Development Board is held like a tape recorder in front of the mouth.
The other microphone is used during voice cell-phone calls when the SA-1110 Development Board
is held like a phone. The audio mixing functions in the SA-1110 Development Board allow the
selection of which microphone to use for voice or using both microphones for high quality stereo
recording.
A 2.5 mm jack is provided for a headset/microphone and a 3.5 mm stereo jack is provided for
stereo headphones. An internal three pin header is provided to allow connections to stereo line in
signals.
4.12.5 SA-1110 Development Board Stereo Codec Sampling Rates
The SA-1110 Development Module UDA1341 does not include a sample rate clock generator.
Therefore, when web browsing, the following sample rates are expected:
• 8 KHz
• 11.025 KHz
• 16 KHz
• 22.05 KHz
• 44.1 KHz
To save the cost and power of a dedicated oscillator and clock generator for these frequencies, the
SA-1110 Development Board derives the 11.29 MHz 128 times clock from the CPU memory clock
using a clock “shimming” scheme implemented in the UDA1341 glue logic CPLD. This clock
shimming scheme produces a 11.29 MHz 128 times oversampling clock that is between 1.1% and
0.1% accurate depending on the CPU core clock chosen. A software sample rate converter (SRC)
function is required to up sample the 8, 11, 16, 22 KHz rates to 44 KHz.
4.12.6 Phone Codec and Soft Modem
The UCB1300 Codec from Philips and a DAA telephone line interface from Krypton support
softmodem and speaker phone. The UCB1300 has two codecs: one for the phone line and one for
microphone and speaker or handset.
The UCB1300 handset codec requires different sampling rates than the stereo codec and may be
required to run concurrently with the UDA1341. The SA-1110 Development Board audio mixing
system includes analog to digital to analog functions that allows the UBC1300 digital audio to be
converted to analog, passed to the UDA1341, and then converted back to digital at the 46.8 KHz
sample rate thus avoiding a software sample rate conversion.
The UCB1300 handset codec analog audio input is from UDA1341 analog audio right channel
output. The UDA1341 may be programmed to select between the main microphone or the back
microphone. The UCB1300 handset codec analog audio speaker output is connected to the