User's Manual
Table Of Contents
- GC864 QUAD V2andGC864 DUAL V2Hardware User Guide
- APPLICABILITY TABLE
- 1 Introduction
- 2. Overview
- 3. GC864 Mechanical Dimensions
- 4. GC864-QUAD V2 / GC864-DUAL V2 Module Connections
- 5. Hardware Commands
- 6. Power Supply
- 7. Antenna
- 8. Logic Level Specifications
- 9. Serial Ports
- 10. Audio Section Overview
- 11. General Purpose I/O
- 11.1. GPIO Logic Levels
- 11.2. Using a GPIO Pad as INPUT
- 11.3. Using a GPIO Pad as OUTPUT
- 11.4. Using the RF Transmission Control GPIO4
- 11.5. Using the RFTXMON Output GPIO5
- 11.6. Using the Alarm Output GPIO6
- 11.7. Using the Buzzer Output GPIO7
- 11.8. Magnetic Buzzer Concepts
- 11.9. Using the Temperature Monitor Function
- 11.10. Indication of Network Service Availability
- 11.11. RTC Bypass Out
- 11.12. DAC Converter
- 11.13. ADC Converter
- 12. Assembly the GC864-QUAD V2 / GC864-DUAL V2 on the Board
- 13. Packing System
- 14. Conformity Assessment Issues
GC864 Hardware User Guide
1vv0300874 Rev.0 – 2010-01-25
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved. Page 37 of 64
TIP:
For a minimum implementation, only the TXD and RXD lines can be connected, the
other lines can be left open provided a software flow control is implemented.
9.2. RS232 Level Translation
In order to interface the Telit GC864-QUAD V2 / GC864-DUAL V2 with 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 2.8VCMOS have an absolute maximum input voltage
of 3,1V; 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 / +3.0V (dedicated) power
supply.
This is because in this way the level translator IC outputs on the module side (i.e.
GC864-QUAD V2 / GC864-DUAL V2 inputs) 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.