LE866 DIGITAL VOICE INTERFACE APPLICATION NOTE 80471NT11521A Rev.
APPLICABILITY TABLE PRODUCTS LE866-SV1 SW VER.: 23.00.003 NOTE: The features described in the present document are provided by the products equipped with the software versions equal or higher than the versions shown in the table. See also the Document History chapter. LE866 DIGITAL VOICE INTERFACE APPLICATION NOTE 80471NT11521A Rev.0 • 2017-01-16 Reproduction forbidden without Telit Communications S.p.A.
DISCLAIMER LEGAL NOTICE These Specifications are general guidelines pertaining to product selection and application and may not be appropriate for your particular project. Telit (which hereinafter shall include, its agents, licensors and affiliated companies) makes no representation as to the particular products identified in this document and makes no endorsement of any product.
HIGH RISK MATERIALS Components, units, or third-party products contained or used with the products described herein are NOT fault-tolerant and are NOT designed, manufactured, or intended for use as on-line control equipment in the following hazardous environments requiring fail-safe controls: the operation of Nuclear Facilities, Aircraft Navigation or Aircraft Communication Systems, Air Traffic Control, Life Support, or Weapons Systems (“High Risk Activities").
CONTENTS 1 Introduction 6 Scope 6 Audience 6 Contact Information, Support 6 List of acronyms 7 Text Conventions 8 1.6.
1 INTRODUCTION Scope The present document provides the reader with a guideline concerning the setting and use of the Digital Voice Interface developed on the Telit’s LE866 modules shown in the Applicability Table. This Application Note covers the configurations of the Digital Voice Interface, e.g.: the selections of the voice sampling frequency, the bit number of the voice sample, the audio formats, etc. In addition, the document shows some configurations of a popular Audio Codec connected to the module.
List of acronyms Acronym Description TTSC Telit Technical Support Centre USB Universal Serial Bus DVI Digital Voice Interface DTE Data Terminal Equipment LTE Long Term Evolution I2C Inter-Integrated Circuit I2S Inter-IC Sound MSB Most Significant Bit SIM Subscriber Identification Module ADC Analog – Digital Converter DAC Digital – Analog Converter I/O Input Output GPIO General Purpose Input Output CMOS Complementary Metal – Oxide Semiconductor CLK Clock CS Chip Select RTC
Text Conventions Danger – This information MUST be followed or catastrophic equipment failure or bodily injury may occur. Caution or Warning – Alerts the user to important points about integrating the module, if these points are not followed, the module and end user equipment may fail or malfunction. Tip or Information – Provides advice and suggestions that may be useful when integrating the module. All dates are in ISO 8601 format, i.e. YYYY-MM-DD. 1.6.
2 OVERVIEW The aim of this document is the description of some hardware solutions useful for developing a product with the Telit LE866 module. In this document all the basic functions of a mobile phone will be taken into account; for each one of them a proper hardware solution will be suggested and eventually the wrong solutions and common errors to be avoided will be evidenced. Obviously this document cannot embrace the whole hardware solutions and products that may be designed.
3 DVI OVERVIEW Before dealing with the configuration and technical aspects of the Telit’s Digital Voice Interface (DVI) it is useful to illustrate briefly how this interface can be used, refer to fig. 1. The voice coming from the downlink, in digital format, is captured by the dedicated software running on the Telit’s module and directed to the Digital Voice Interface. The Audio Codec decodes the voice and sends it to the speaker.
4 DVI BUS DVI PIN LIST The physical DVI interface provided by the Telit’s modules is based on the standard I2S Bus. An overview of the standard I2S Bus is described in chapter 6.1. The following Table summarizes the DVI signals and a short description for each one of them; refer to Telit Hardware User Guide, in accordance with the used module, to have information on electrical characteristics and signals pin-out.
5 DVI AT COMMANDS Several DVI audio bus configurations are available via AT#DVI and AT#DVIEXT commands. The tables in the following sub-sections summarize their parameters; refer to the AT Commands User Guide for the syntax details. AT#DVI The DVI signals are Alternate functions of GPIOs 1, 2, 3 and 4. The AT#DVI command enables/disables the DVI interface, selects the DVI port, and sets the module in Master or Slave configuration. The table below shows the AT command parameters values.
AT#DVIEXT AT#DVIEXT command sets the module in Normal or Burst DVI Audio Format: In Normal DVI Audio Format the WAO signal defines the left and right audio channel. In Burst DVI Audio Format the WAO signal defines the beginning of the audio frame. The following table shows the AT command parameters values.
LE866 DIGITAL VOICE INTERFACE APPLICATION NOTE 80471NT11521A Rev.0 • 2017-01-16 Reproduction forbidden without Telit Communications S.p.A.
6 DVI SETTING EXAMPLES The next chapters show examples concerning the audio formats supported by the DVI audio bus in Master and Slave configurations. All the following setting examples are performed using the hardware configuration shown in fig. 3. I2C bus is used to configure the MAX9867 Codec: the user by means of AT commands can control the codec. The DVI bus provides the voice connection between the two devices. fig.
Normal (I2S) Mode Module is Master In this configuration the WAO and CLK signals are generated by the module. The WAO signal defines the frame of the two audio channels: left and right, refer to fig. 5. The BitClockFrequency (CLK) is provided by the following expression: BitClockFr equency DataWordBit ChannelNumber AudioSampleRate The BitClockFrequency values are shown in Tab. 4.
Configure the codec in Slave/Normal (I2S) Mode (I2C Bus) AT#I2CWR=X,Y,30,4,19 >00109000100A330000330C0C09092424400060 OK X GPIO number used as SDA, refer to AT User Guide Y GPIO number used as SCL, refer to AT User Guide 30 Device address on I2C, refer to MAX9867 documentation 4 19 Register address from which start the writing, refer to MAX9867 documentation number of bytes to write >00109000…..
The fig. 5 shows the screenshot of the timing diagram, captured by a logic analyzer, using the above described module/codec setting. The CLK (512 KHz) and WAO signals are generated by the module, data is transmitted on the rising edge of clock and sampled on the falling edge.
7 ANNEX I2S Bus Overview This chapter provides a short description of the standard I2S bus. This standard suitably modified is used by the DVI interface implemented on the Telit modules. The standard I2S is an electrical serial bus designed for connecting digital audio devices. This popular serial bus has been developed by Philips® in 1986 as a 3-wire bus for interfacing to audio chips such as codecs. It is a simple data interface, without any form of address or device selection. Refer to fig.
Schematic A schematic example of an interface between a Telit Module and the MAX9867 Codec could be the following: LE866 DIGITAL VOICE INTERFACE APPLICATION NOTE 80471NT11521A Rev.0 • 2017-01-16 Reproduction forbidden without Telit Communications S.p.A.
8 DOCUMENT HISTORY Revisions Revision Date 0 2017-01-16 Changes Initial Version LE866 DIGITAL VOICE INTERFACE APPLICATION NOTE 80471NT11521A Rev.0 • 2017-01-16 Reproduction forbidden without Telit Communications S.p.A.
