Rainbow Electronics GM862-QUAD-PY - Manual (Page 3)

GM862-QUAD / PY Hardware User Guide
1vv0300748 Rev. 5 - 20/09/07
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 3 of 68
8.1 Microphone Paths Characteristic and Requirements ....................................................... 38
8.2 General Design Rules .......................................................................................................... 41
8.3 Other Considerations ........................................................................................................... 41
8.4 Microphone Biasing ............................................................................................................. 42
8.4.1 Balanced Microphone Biasing ........................................................................................................42
8.4.2 Unbalanced Microphone Biasing ....................................................................................................43
8.5 Microphone Buffering .......................................................................................................... 45
8.5.1 Buffered Balanced Mic ....................................................................................................................45
8.5.2 Buffered Unbalanced (Single Ended) Microphone .........................................................................47
9 OUTPUT LINES (Speaker) .............................................................................................. 50
9.1 Short Description ................................................................................................................. 50
9.2 Output Lines Characteristics .............................................................................................. 51
9.3 General Design Rules .......................................................................................................... 52
9.3.1 Noise Filtering .................................................................................................................................52
9.4 Handset Earphone Design ................................................................................................... 53
9.5 Hands-Free Earphone (Low Power) Design ....................................................................... 54
9.6 Car Kit Speakerphone Design ............................................................................................. 55
10 General Purpose I/O ....................................................................................................... 56
10.1 GPIO Logic levels ................................................................................................................. 58
10.2 Using a GPIO pin as INPUT ................................................................................................. 59
10.3 Using the RF Transmission Control GPIO4 ....................................................................... 59
10.4 Using the RFTXMON Output GPIO5 .................................................................................... 59
10.5 Using the Alarm Output GPIO6 ........................................................................................... 59
10.6 Using the Buzzer Output GPIO7 .......................................................................................... 60
11 ADC section .................................................................................................................... 61
11.1 ADC converter ...................................................................................................................... 61
11.1.1 Description ......................................................................................................................................61
11.1.2 Using ADC Converter .....................................................................................................................61
12 Indication of network service availability ..................................................................... 62
13 Mounting the GM862 Modules on your Board ............................................................. 63
13.1 Antenna Coaxial Cable Fixing ............................................................................................. 64
13.2 Precautions ........................................................................................................................... 65
14 Conformity Assessment Issues .................................................................................... 66
15 SAFETY RECOMMANDATIONS..................................................................................... 67
16 Document Change Log .................................................................................................. 68