LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 70 of 125
The circular buffer is a 3000 word buffer to store and mix the voice-band samples from Midi synthesizer. The
buffer has a circular structure, so that when the write pointer reaches the end of the buffer, it is wrapped to the
begin address of the buffer.
Two different sample-based sample rate converters are used: an interpolator, required to convert the sample-
based voice-band processing sampling rate of 8 kHz to the analog audio front-end output rate of 47.6 kHz; a
decimator, required to convert the circular buffer sampling rate of 47.6 kHz to the I2Sx TX or the uplink path
sample rate of 8 kHz.
1.10.3.1
Audio codecs
The following speech codecs are supported by firmware on the DSP:
GSM Half Rate (TCH/HS)
GSM Full Rate (TCH/FS)
GSM Enhanced Full Rate (TCH/EFR)
3GPP Adaptive Multi Rate (AMR) (TCH/AFS+TCH/AHS)
1.10.3.2
Echo cancelation and noise reduction
LEON-G100 / LEON-G200 support algorithms for echo cancellation, noise suppression and automatic gain
control. Algorithms are configurable with AT commands (refer to the
u-blox AT Commands Manual
1.10.3.3
Digital filters and gains
Audio parameters such as digital filters, digital gain, Side-tone gain (feedback from uplink to downlink path) and
analog gain are available for uplink and downlink audio paths. These parameters can be modified by dedicated
AT commands and be saved in 2 customer profiles in the non-volatile memory of the module (refer to the
u-blox
AT Commands Manual
1.10.3.4
Ringer mode
LEON-G100 / LEON-G200 modules support polyphonic ring tones. The ringer tones are generated by a built-in
generator on the chipset and then amplified by the internal amplifier.
The synthesizer output is only mono and cannot be mixed with TCH voice path (the two are mutually exclusive).
To perform in-band alerting during TCH with voice path open, only Tone Generator can be used.
The analog audio path used in ringer mode can be the high power differential audio output (refer to
u-blox AT
Commands Manual
[2]; AT+USPM command, <main_downlink> and <alert_sound> parameters for alert sounds
routing). In this case the external high power loudspeaker must be connected to the
SPK_P
/
SPK_N
output pins
of the module as shown in the application circuit (Figure 38) described in section 1.10.1.5.
1.11
ADC input (LEON-G100 only)
One Analog to Digital Converter input is available (
ADC1
) and is configurable using u-blox AT command (see
u-blox AT Commands Manual
[2]). The resolution of this converter is 12-bit with a single ended input range.
Name
Description
Remarks
ADC1
ADC input
Resolution: 12 bits.
Table 27: ADC pin
ADC1
pin ESD sensitivity rating is 1 kV (HBM JESD22-A114F). A higher protection level could be
required if the line is externally accessible on the application board. A higher protection level can be
achieved mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on the line
connected to this pin if it is externally accessible on the application board.
