User Manual
Table Of Contents
- 1. Introduction
- 2. GR47/GR48 Radio Devices
- 3. Abbreviations
- 4. Mechanical Description
- 5. System Connector Interface
- 5.1 Overview
- 5.2 General Electrical and Logical Characteristics
- 5.3 Grounds
- 5.4 VCC - Regulated Power Supply Input
- 5.5 Battery Charging Input (CHG_IN)
- 5.6 Turning the Radio Device ON/OFF and the External Power Signal
- 5.7 Analogue Audio
- 5.8 PCM Digital Audio
- 5.9 Serial Data Interfaces
- 5.10 SIM Card Related Signals
- 5.11 Service/Programming
- 5.12 Buzzer
- 5.13 LED
- 5.14 General Purpose Digital I/O Ports
- 5.15 Extended I/O capabilities
- 5.16 General Purpose Analogue I/O Ports
- 5.17 External I 2C Serial Control Bus
- 5.18 TX_ON - Burst Transmission
- 5.19 Real Time Clock
- 6. Antenna Connector
- 7. Keyboard Interface
- 8. Hints for Integrating the Radio Device
- 9. Embedded Applications
- 10. TCP/IP Stack
- 11. Technical Data
- 12. Declaration of Conformity
- 13. Introduction to the Developer’s Kit
- 14. Using the Developer’s Kit
7. KEYBOARD INTERFACE
52
LZT 123 7589 R1A
7. Keyboard Interface
To increase I/O capabilities, the radio device optimises the I/O by
multiplexing or sharing different features on single pins. The I/O has been
extended to allow simple interfacing of a matrix keypad.
7.1 IO#/KEYROW#
When configured for keypad operation the software will configure the dig-
ital I/O pins as input or high impedance tri-state. In this state, the keypad
matrix row can be read from the KEYROW# inputs. These pins have a
100kΩ pull-up to 2.75V and the rows are considered activated when the
voltage is pulled low by the external keypad switches.
7.2 KEYCOL#
The keypad matrix column drivers share functionality with the RS232
hardware flow control signals.
In addition to the keypad column outputs it is possible to use a direct
ground connection as an additional column driver, which is interpreted as
column zero.
Simply connect one keypad column directly to ground. When a key in this
column is depressed KEYROW# is activated.
Thus it is possible to create a variety of keypad matrix sizes from single
column to five columns wide.
Finally, a standard keypad matrix directly connects the rows to the
columns whenever a key is depressed. In order to avoid short circuits if
multiple keys are pressed simultaneously, the column drivers must be
open-collector. This must be achieved with external transistors as the logic
drive from the radio device is rail-to-rail. Suitable transistors for this
interface are of the type with built in bias resistors between base and
emitter.