User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 72 of 116
 I2S_WA signal always runs at 8 kHz and synchronizes 2 channels (timeslots on WA high, WA low)
 I2S_TX data are composed of 16 bit words, dual mono (the words are written on both channels). Data are
in 2’s complement notation. MSB is transmitted first. The bits are written on I2S_CLK rising or falling edge
(configurable)
 I2S_RX data are read as 16 bit words, mono (words are read only on the timeslot with WA high). Data is
read in 2’s complement notation. MSB is read first. The bits are read on the I2S_CLK edge opposite to
I2S_TX writing edge (configurable)
 I2S_CLK frequency is 16 bits x 2 channels x 8 kHz = 256 kHz
The modes are configurable through a specific AT command (refer to the related chapter in u-blox AT
Commands Manual [2], +UI2S AT command) and the following parameters can be set:
 MSB can be 1 bit delayed or non-delayed on I2S_WA edge
 I2S_TX data can change on rising or falling edge of I2S_CLK signal (rising edge in this example)
 I2S_RX data are read on the opposite front of I2S_CLK signal
1.11.3 Voiceband processing system
The voiceband processing on the LISA-U120 and LISA-U130 modules is implemented in the DSP core inside the
baseband chipset. The analog audio front-end of the chipset is connected to the digital system through 16 bit
ADC converters in the uplink path, and through 16 bit DAC converters in the downlink path. External digital
audio devices can be interfaced directly to the DSP digital processing part via the I
2
S digital interface. The analog
amplifiers are skipped in this case.
Possible processing of audio signal are:
 Speech encoding (uplink) and decoding (downlink).The following speech codecs are supported in firmware
on the DSP:
 Fullrate, enhanced full rate, and half rate speech encoding and decoding
 Adaptive multi rate (full rate and half rate) speech encoding and decoding
 Mandatory sub-functions:
 Discontinuous transmission, DTX (GSM 46.031, 46.041, 46.081 and 46.093 standards)
 Voice activity detection, VAD (GSM 46.032, 46.042, 46.082 and 46.094 standards)
 Background noise calculation (GSM 46.012, 46.022, 46.062 and 46.092 standards)
 Function configurable via specific AT commands (refer to the u-blox AT Commands Manual [2])
 Signal routing: +USPM command
 Analog amplification, Digital amplification: +USGC,+CLVL, +CRSL, +CMUT command
 Digital filtering: +UUBF, +UDBF commands
 Hands-free algorithms (echo cancellation, Noise suppression, Automatic Gain control) +UHFP command
 Sidetone generation (feedback of uplink speech signal to downlink path): +USTN command
 Playing/mixing of alert tones:
Service tones: Tone generator with 3 sinus tones +UPAR command
User generated tones: Tone generator with 3 sinus tones +UTGN command
Midi melodies (for ringer): Synthesizer with up to 64 voices and a 48 kHz sampling rate, +UPAR
command
AMR files (for prompting): The storage format of AMR encoded audio content is defined in RFC3267
chapter 5 [9], +UPLAYFILE command
With exception of the speech encoder/decoder, this audio processing can be controlled by AT commands.
This processing is implemented within three different blocks of the voiceband processing system: