Owner's manual
GM862-GPS Hardware User Guide
1vv0300728 Rev. 8 - 20/09/07
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 3 of 73
8.1 Microphone Paths Characteristic and Requirements ....................................................... 43
8.2 General Design Rules .......................................................................................................... 46
8.3 Other Considerations ........................................................................................................... 46
8.4 Microphone Biasing ............................................................................................................. 47
8.4.1 Balanced Microphone Biasing ........................................................................................................47
8.4.2 Unbalanced Microphone Biasing ....................................................................................................48
8.5 Microphone Buffering .......................................................................................................... 50
8.5.1 Buffered Balanced Mic ....................................................................................................................50
8.5.2 Buffered Unbalanced (Single Ended) Microphone .........................................................................52
9 OUTPUT LINES (Speaker) .............................................................................................. 55
9.1 Short Description ................................................................................................................. 55
9.2 Output Lines Characteristics .............................................................................................. 56
9.3 General Design Rules .......................................................................................................... 57
9.3.1 Noise Filtering .................................................................................................................................57
9.4 Handset Earphone Design ................................................................................................... 58
9.5 Hands-Free Earphone (Low Power) Design ....................................................................... 59
9.6 Car Kit Speakerphone Design ............................................................................................. 60
10 General Purpose I/O ....................................................................................................... 61
10.1 GPIO Logic levels ................................................................................................................. 63
10.2 Using a GPIO pin as INPUT ................................................................................................. 64
10.3 Using a GPIO pin as OUTPUT ............................................................................................. 64
10.4 Using the RF Transmission Control GPIO4 ....................................................................... 64
10.5 Using the RFTXMON Output GPIO5 .................................................................................... 64
10.6 Using the Alarm Output GPIO6 ........................................................................................... 65
10.7 Using the Buzzer Output GPIO7 .......................................................................................... 65
11 ADC section .................................................................................................................... 66
11.1 ADC converter ...................................................................................................................... 66
11.1.1 Description ......................................................................................................................................66
11.1.2 Using ADC Converter .....................................................................................................................66
12 Indication of network service availability ..................................................................... 67
13 Mounting the GM862 module on your Board ............................................................... 68
13.1 Antenna Coaxial Cable Fixing ............................................................................................. 69
13.2 Precautions ........................................................................................................................... 70
14 Conformity Assessment Issues .................................................................................... 71
15 SAFETY RECOMMANDATIONS..................................................................................... 72