Telit Wireless Solutions GM862-GPS Hardware User's Manual
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Telit Wireless Solutions GM862-GPS Hardware User's Manual

Telit Wireless Solutions GM862-GPS Hardware User's Manual

Telit wireless solutions gm862-gps hardware user guide
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GM862-GPS Hardware User Guide
GM862-GPS HW User Guide
1vv0300728 Rev. 0 - 27/04/06

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Summary of Contents for Telit Wireless Solutions GM862-GPS

  • Page 1 GM862-GPS Hardware User Guide GM862-GPS HW User Guide 1vv0300728 Rev. 0 - 27/04/06...

  • Page 2: Table Of Contents

    Contents Overview ...4 Hardware Commands ...5 Turning ON the GM862-GPS ...5 Turning OFF the GM862-GPS ...7 2.2.1 Hardware shutdown...7 2.2.2 Hardware Unconditional Reboot...8 Power Supply ...10 Power Supply Requirements ...10 General Design Rules ...11 3.2.1 Electrical design Guidelines... 11 3.2.1.1 + 5V input Source Power Supply Design Guidelines ...

  • Page 4: Overview

    Telit GM862-GPS modules. For further hardware details that may not be explained in this document refer to the GM862-GPS/-QUAD-PY Product Description document where all the hardware information is reported. NOTE: In this document all the hardware solution are referenced to the GM862-GPS.

  • Page 5: Hardware Commands

    Hardware Commands 2.1 Turning ON the GM862-GPS To turn on the GM862-GPS the pin ON# must be tied low for at least 1 second and then released. The maximum current that can be drained from the ON# pin is 0,1 mA.
  • Page 6 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 For example: 1- Let's assume you need to drive the ON# pin with a totem pole output of a +3/5 V microcontroller (uP_OUT1): 2- Let's assume you need to drive the ON# pin directly with an ON/OFF button: Reproduction forbidden without Telit Communications S.p.A.

  • Page 7: Turning Off The Gm862-Gps

    2.2.1 Hardware shutdown To turn OFF the GM862-GPS the pin ON# must be tied low for at least 1 second and then released. The same circuitry and timing for the power on shall be used. The device shuts down after the release of the ON# pin.

  • Page 8: Hardware Unconditional Reboot

    NOTE: don't use any pull up resistor on the RESET# line nor any totem pole digital output. Using pull up resistor may bring to latch up problems on the GM862-GPS power regulator and improper functioning of the module. The line RESET# must be connected only in open collector configuration.
  • Page 9 If device does not respond to a command in the timeout window, retry issuing the command and if still no response is received a hardware unconditional reboot shall be issued. Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 page 9 of 55...

  • Page 10: Power Supply

    The power supply circuitry and board layout are the most important part in the full product design and they strongly reflect on the product overall performances, hence read carefully the requirements and the guidelines that will follow for a proper design. 3.1 Power Supply Requirements The GM862-GPS power requirements are: • Nominal Supply Voltage: •...

  • Page 11: General Design Rules

    Make sure the low ESR capacitor on the power supply output (usually a tantalum one) is rated at least 10V. • A protection diode should be inserted close to the power input, in order to save the GM862-GPS from power polarity inversion. Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev.
  • Page 12 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 An example of linear regulator with 5V input is: Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 12 of 55...

  • Page 13: Input Source Power Supply Design Guidelines

    • A protection diode should be inserted close to the power input, in order to save the GM862-GPS from power polarity inversion. This can be the same diode as for spike protection. Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev.

  • Page 14: Battery Source Power Supply Design Guidelines

    GM862-GPS and damage it. NOTE: DON'T USE any Ni-Cd, Ni-MH, and Pb battery types. Their use can lead to overvoltage on the GM862-GPS and damage it. USE ONLY Rechargeable Li-Ion battery types.

  • Page 15: Battery Charge Control Circuitry Design Guidelines

    5% or less. This last phase is not implemented in the GM862-GPS internal charging algorithm, so that the battery once charged is left discharging down to a certain threshold so that it is cycled from full charge to slight discharge even if the battery charger is always inserted.
  • Page 16 5°C - 45°C. The GM862-GPS measures the temperature of its internal component, in order to satisfy this last requirement, it's not exactly the same as the battery temperature but in common application the two temperature should not differ too much and the charging temperature range should be guaranteed.

  • Page 17: Thermal Design Guidelines

    For these reasons the thermal design is rarely a concern and the simple ground plane where the power supply chip is placed can be enough to ensure a good thermal condition and avoid overheating. Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 500mA...

  • Page 18: Power Supply Pcb Layout Guidelines

    • The Bypass low ESR capacitor must be placed close to the Telit GM862-GPS power input pins or in the case the power supply is a switching type it can be placed close to the inductor to cut the ripple provided the PCB trace from the capacitor to the GM862-GPS is wide enough to ensure a dropless connection even during the 2A current peaks.

  • Page 19: Serial Ports

    The GPS Serial Port is a 3 wire (RX, TX GND) +2.8V UART. The MODEM serial port on the GM862-GPS is a +2.8V UART with all the 7 RS232 signals. It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels. The levels for the GM862-...
  • Page 20 RI - ri_uart NOTE: According to V.24, RX/TX signal names are referred to the application side, therefore on the GM862-GPS side these signal are on the opposite direction: TXD on the application side will be connected to the receive line (here named TXD/ rx_uart ) of the GM862-GPS serial port and viceversa for RX.

  • Page 21: Level Translation

    IC shall not be powered by the +3.8V supply of the module. Instead it shall be powered from a +2.8V / +3.0V (dedicated) power supply. This is because in this way the level translator IC outputs on the module side (i.e. GM862-GPS inputs) will work at +3.8V interface levels, stressing the module inputs at its maximum input voltage.
  • Page 22 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 An example of level translation circuitry of this kind is: the RS232 serial port lines are usually connected to a DB9 connector with the following layout: Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved...

  • Page 23: Uart Level Translation

    GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 4.2 5V UART level translation If the OEM application uses a microcontroller with a serial port (UART) that works at a voltage different from 2.8 - 3V, then a circuitry has to be provided to adapt the different levels of the two set of signals.
  • Page 24 1vv0300728 Rev. 0 - 27/04/06 NOTE: The UART input line TXD (rx_uart) of the GM862-GPS is NOT internally pulled up with a resistor, so there may be the need to place an external 47KΩ pull-up resistor, either the DTR (dtr_uart) and RTS (rts_uart) input lines are not pulled up internally, so an external pull-up resistor of 47KΩ...

  • Page 25: Audio Section Overview

    5 Audio Section Overview The Base Band Chip of the GM862-GPS Telit Module provides two different audio blocks; both in transmit (Uplink) and in receive (Downlink) direction: “MT lines” should be used for handset function, “HF lines” is suited for hands -free function (car kit).
  • Page 26 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 EXTERNAL AMPLIFIER 3,3mV 0,33mV Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 26 of 55...

  • Page 27: Microphone Paths Characteristic And Requirements

    • analog gain suggested • echo canceller type Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 balanced ≥ 100nF 50kΩ ≤ 1,03V (365mV -45 dBV...
  • Page 28 TIP: definition of the nominal sensitivity of the microphone lines . The nominal sensitivity of the microphone lines indicates the voltage level on the GM862-GPS pins present during "normal spoken" conditions. For a handset , the "normal spoken” conditions take place when the talker mouth is 7cm far from the microphone ;...
  • Page 29 “Mic_HF” Level = 0,33* 10 * 3=1* 10 Hence in these conditions the signal level on the“Mic_HF” input pads of the GM862-GPS is 10 dB (3 times) lower than the nominal, as suggested. Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved...

  • Page 30: General Design Rules

    ; • try to make divergent the main axes of the two devices . Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 page 30 of 55...

  • Page 31: Microphone Biasing

    GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 5.4 Microphone Biasing The electret microphones usually need a biasing voltage to work properly. Refer to your microphone provider for the characteristics required. NOTE: The microphones have a hot wire were the positive biasing must be connected. Usually it is indicated by a + symbol or a red point.

  • Page 32: Unbalanced Microphone Biasing

    GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 NOTE: The cable to the microphone should not be shielded, instead a twisted pair cable shall be used. NOTE: The microphone sensitivity changes with the value of R2 and R3. Usually the microphones are characterized with 2kΩ...
  • Page 33 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 NOTE: In the unbalanced application the capacitor C3 shall be > 200nF otherwise the frequency response will be cut at low band frequencies (down to 300Hz). This capacitor can be placed close to the MIC- pad (MIC_HF- or MIC_MT- depending on the audio path chosen) or if possible it should be placed close to the shielded cable connector.

  • Page 34: Microphone Buffering

    1vv0300728 Rev. 0 - 27/04/06 5.5 Microphone buffering As seen previously, a microphone shall be connected to the input pins of the GM862-GPS through a buffer amplifier that boosts the signal level to the required value. Again the buffered microphone circuitry can be balanced or unbalanced: where possible it is always preferable a balanced solution.
  • Page 35 C636=C637= 1/ (2π*4000*R606)= 265 *10 A commercial value of 270pF gives a cutoff frequency of 3931Hz with an errorless than 1,8% . Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide Gain π...

  • Page 36: Buffered Unbalanced (Single Ended) Microphone

    The -3dB bandwidth is given by the approximated formula (considering C725 >> C726): freq Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved Gain inverting π π GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 2,7nF 6,8nF buffer [Hz] page 36 of 55...
  • Page 37 /MicVoltage = (1*10 R711 = G * R708= 1.5*10 =15 kΩ -1) * R720 = (1.5 -1)*10 =5 kΩ GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 /Pa and you want to use it in 2nd or +10 dB )/(0,33*10 =1,5times (or +3,52dB) .
  • Page 38 6,8nF (f =4181Hz ) and 2,7nF (f Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide =3931Hz) because of commercial values . 1vv0300728 Rev. 0 - 27/04/06 page 38 of 55...

  • Page 39: Output Lines (Speaker)

    OUTPUT LINES (Speaker) 6.1 Short description. The Telit GM862-GPS provides two audio paths in receive section. Only one of the two paths can be active at a time, selectable by AXE hardware line or by AT command. You must keep in mind the different audio characteristics of the receive blocks when designing : the “Ear_MT”...

  • Page 40: Output Lines Characteristics

    • SW volume level step • number of SW volume steps Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 bridged ≥ 14 Ω 4 Ω (typical) 150 - 4000 Hz @ -3 dB...

  • Page 41: General Design Rules

    The three groups have different power requirements, usually the first two applications need only few mW of power, which can be directly drained from the GM862-GPS pads, provided a suited speaker is used. This direct connect design is the cheaper and simpler solution and will be suited for the most of the earphone design requirements.
  • Page 42 (if speaker impedance is bigger than 16Ω) or the GM862-GPS ear port may be damaged (if speaker impedance is less than 15Ω).
  • Page 43 6.5 Hands-free earphone (low power) design The same design considerations made for the handset are valid for the hands-free earphone. Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide Gain = freq [Hz] π...
  • Page 44 The design of the amplifier shall comply with the following guidelines: • The input to the amplifier MUST be taken from the “Ear_HF” audio path of the GM862-GPS, because of its echo canceller parameters suited to a car cabin use.
  • Page 45 Input pins can only be read and report the digital value (high or low) present on the pin at the read time; output pins can only be written or queried and set the value of the pin output; an alternate function pin is internally controlled by the GM862-GPS firmware and acts depending on the function implemented.
  • Page 46 1vv0300728 Rev. 0 - 27/04/06 7.3 Using the Alarm Output GPIO6 The GPIO6 pin, when configured as Alarm Output, is controlled by the GM862-GPS module and will rise when the alarm starts and fall after the issue of a dedicated AT command.

  • Page 47: Gps Receiver

    Impedance Amplification Supply voltage Current consumption Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide ANTENNA REQUIREMENTS 1575.42 MHz (GPS L1) +- 1.023 MHz 1.5 dBi < Gain < 4.5 dBi 50 ohm...
  • Page 48 9 Camera 9.1 Camera Transchip The GM862-GPS provides a direct support for Transchip digital cameras with the following characteristics: Type: Technology: Max picture size: Output format: Sensitivity: 9.1.1 Camera interface connectors The 50-pins Molex connector of the module and a 24 pins ZIF connector for the CMOS camera provide the interface connection between GM862 and Transchip camera.
  • Page 49 Use a Buffer between module clk out, MON1_CAM and camera clk in, CLK_IN. Non-connected. 9.1.2 EVB for camera support In order to interface the Telit GM862-GPS with a CMOS camera, Telit has developed an evaluation board. The EVB is provided by: •...
  • Page 50 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 Camera Socket Connector 9.1.3 Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 50 of 55...

  • Page 51: Main Board

    The I2CBUS DUAL CAMERA board is plugged in the 2 connectors of 30 pins each on the module board. CAMERA BOARD MODULE BOARD MAIN BOARD Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 page 51 of 55...
  • Page 52 9.1.4 Block Diagram for supported camera DVDD is an external power supply of 2.8V, controlled or gated by pin CAM_PWR_ON. DVDD MON1_CAM Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide CAMERA TRANSCHIP PD[6] AVDD PD[1]...
  • Page 53 GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 9.1.5 Schematic Diagrams for supported cameras Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 53 of 55...
  • Page 54 >AT#CAMEN=O (camera OFF) *only Transchip camera Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide (camera quality: 0-low, 1-medieum, 2-high) (camera resolution: 0-VGA, 1-QVGA, 2-QQVGA) (camera color: 0-color, 1-grayscale) (camera zoom: 0-x1, 1-x2, 2-x4) (camera timestamp: 0-no, 1-time only, 2-data only, 3-time&data)

  • Page 55: Document Change Log

    10 Document Change Log ISSUE#0 27/04/06 Release First ISSUE# 0 Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved GM862-GPS Hardware User Guide 1vv0300728 Rev. 0 - 27/04/06 page 55 of 55...

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