Telit Wireless Solutions 1vv0300773a manual RS232 level translation

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GE863-PRO3Hardware User Guide

1vv0300773a Rev. 0 - 24/01/08

7.2 RS232 level translation

In order to interface the Telit GE863-PRO3with a PC com port or a RS232 (EIA/TIA-232) application a level translator is required. This level translator must

•invert the electrical signal in both directions

•change the level from 0/3V to +15/-15V

Actually, the RS232 UART 16450, 16550, 16650 & 16750 chipsets accept signals with lower levels on the RS232 side (EIA/TIA-562) , allowing for a lower voltage-multiplying ratio on the level translator. Note that the negative signal voltage must be less than 0V and hence some sort of level translation is always required.

The simplest way to translate the levels and invert the signal is by using a single chip level translator. There are a multitude of them, differing in the number of driver and receiver and in the levels (be sure to get a true RS232 level translator not a RS485 or other standards).

By convention the driver is the level translator from the 0-3V UART level to the RS232 level, while the receiver is the translator from RS232 level to 0-3V UART.

In order to translate the whole set of control lines of the UART you will need:

•5 driver

•3 receiver

NOTE: The digital input lines working at 2.8V/3.1VCMOS have an absolute maximum input voltage of 3,75V; therefore the level translator IC shall not be powered by the +3.8V supply of the module. Instead it shall be powered from a +2.8V / +3.1V (dedicated or 3.1V_OUT) power supply.

This is because in this way the level translator IC outputs on the module side (i.e. GE863-PRO3inputs) will work at +3.8V interface levels, stressing the module inputs at its maximum input voltage.

This can be acceptable for evaluation purposes, but not on production devices.

NOTE: In order to be able to do in circuit reprogramming of the GE863-PRO3GPRS firmware, the serial port on the Telit GE863-PRO3shall be available for translation into RS232 and either it's controlling ARM device shall be placed into tristate, disconnected or as a gateway for the serial data when module reprogramming occurs.

Only RXD, TXD, GND and the On/off module turn on pad are required to the reprogramming of the module, the other lines are unused.

All applicator shall include in their design such a way of reprogramming the GE863-PRO3.

NOTE: In order to be able to do in circuit reprogramming of the GE863-PRO3ARM Application software, the serial port DEBUG on the Telit GE863-PRO3shall be available for translation into RS232 when module reprogramming occurs.

Only DRXD, DTXD, GND and the ON/OFF*-AP module turn on pad are required to the reprogramming of the module, the other lines are unused.

All applicator shall include in their design such a way of reprogramming the GE863-PRO3.

Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved

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Contents GE863-PRO3Hardware User Guide Contents GE863-PRO 3 Hardware User Guide This document is relating to the following products Disclaimer Overview Length 41,4 mm Width 31,4 mm Thickness 3,6 mm GE863-PRO3Mechanical DimensionsTelit GE863-PRO3module overall dimension are GE863-PRO3module connections C2 Vbatt C3 Vrtc DTE GPIO7 / Rftxdisable GSMC11 Simrst C12 Simio D1 Charge D2 VAUX1 D10 GND D11 Simvcc D12 Simclk E1 GND E2 PwrmonPB8 Nrst Reset ARMPB9 ON/OFF*-APPB2 PB0PB1 PB7XIN32 HdmbXOUT32 PA3Reserved GND VBATT2Balls Layout ARM PIO Controller a multiplexing ARM Port IO multiplexingARM PIO Controller B multiplexing ARM PIO Controller C multiplexing Turning on the GE863-PRO3GSM/GPRS Engine Hardware Commands+1,8/5 10kHardware shutdown Hardware Unconditional Reboot of GSM/GPRS Engine2Turning OFF the GE863-PRO3GSM/GPRS Engine Turning ON/OFF the GE863-PRO3ARM ON/OFF*-AP # GND GSM Power Supply Requirements Power SupplyAT+CFUN=1 AT+CFUN=4Vrtc Backup supply ARM Power Supply RequirementsElectrical design Guidelines General Design RulesSuggested circuit is 817A19A Seiko1.1 + 5V input Source Power Supply Design Guidelines 1.2 + 12V input Source Power Supply Design Guidelines Battery Source Power Supply Design Guidelines Battery Charge control Circuitry Design Guidelines GE863-PRO3Hardware User Guide Thermal Design Guidelines Power Supply PCB layout Guidelines GSM Antenna Requirements Antenna50 ohm GSM Antenna PCB line GuidelinesElectro Magnetic Interference Guidelines GSM Antenna installation GuidelinesOperating Range Interface levels Cmos Level Min Max Logic level specificationsAbsolute Maximum Ratings -Not Functional Parameter Min Max Cmos 3.1V Current characteristics Level Typical GSM Gpio Current characteristics Level TypicalCmos 1.8V-A Current characteristics Level Typical Operating Range Interface levels Cmos Vrtc Level Min MaxSignal Min Max Signal FunctionPhone reset Modem Serial Port Modem Serial Port 2 Debug Serial PortsSignals of the GE863-PRO3GSM/GPRS engine serial port are RS232 level translation An example of level translation circuitry of this kind is GE863-PRO3Hardware User Guide Audio Section Overview Short description Input Lines MicrophoneMicmt 1st differential microphone path Input Lines CharacteristicsOutput Lines Speaker Earmt Differential Line-out Drivers Path Output Lines CharacteristicsEvaluation Kit for Telit GE863- PRO3 Modules ON/OFF 10 GSM/GPRS General Purpose I/OUsing a Gpio Pad as Output Using a Gpio Pad as InputUsing the RF Transmission Control GPIO7 10.4Using the Rftxmon Output GPIO3Using the Buzzer Output GPIO4 Using the Alarm OutputDevice Status 10.7Indication of network service availabilityLED status RTC Bypass out 10.9VAUX1 power outputOperating Range VAUX1 power supply 11.1General Mounting the GE863-PRO3on the Application BoardStencil PCB pad DesignSolder paste Following is the recommended solder reflow profile 11.1.4 GE863-PRO3Solder Reflow3C/second max Section A-A Packing SystemModules orientation on tray Moisture Sensibility Conformity Assessment Issues Safety Recommandations Revision Date Changes Document Change Log

1vv0300773a specifications

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