Isdnsync » History » Version 11
dexter, 02/19/2016 10:47 PM
| 1 | 9 | dexter | Note: This Howto is still incomplete and will be finished soon. Please do not try anything described in this howto unless we have checked and verified everything with our own equipment! |
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| 2 | 6 | dexter | --------------------------------------------------------------- |
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| 5 | 7 | dexter | == Abstract == |
| 6 | 6 | dexter | |
| 7 | 11 | dexter | In a state of the art telephone network everything is syncronized by a central, very high accuracy clock. The BTS also uses this clock for various things like channel allocation, frame clock, bitclock ect. If the clock gets a little bit incorrect (more than 50Hz) the BTS will transmit on a wrong frequency and there will be lots of other effects that might destabilize the radio transmission. |
| 8 | 1 | dexter | |
| 9 | 11 | dexter | The BS11 is shipped with a precalibrated internal oscillator. If you are lucky the calibration (that is made over 10 years ago) in your BTS is still correct. If not your setup will not work unless you recalibrate the oscillator. |
| 10 | 1 | dexter | |
| 11 | This document illustrates how you can use a ceap HFC-S card with the public telephone network as frequency standard for your E1 line. |
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| 13 | 7 | dexter | == Modifieing the HFC-S Card == |
| 14 | 6 | dexter | |
| 15 | 1 | dexter | All in all we need 2 Signals from the HFC-S Card: F0IO and C4IO. This signals are provided by the HFC-S Chip on the card and can be taken from pin 55 (F0IO) and 54 (C4IO) at the HFC-S Chip. (See also Datasheet page 8). |
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| 17 | 4 | dexter | [[Image(hfc-s_card.jpg, 20%)]] |
| 18 | 5 | dexter | |
| 19 | All you need to do is to solder a wire to C4IO and F0I0. The following image shows our modified card: |
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| 20 | 1 | dexter | |
| 21 | [[Image(hfc-s_card_modified.jpg, 20%)]] |
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| 23 | 1 | dexter | |
| 24 | 9 | dexter | == Connecting the modified HFC-S card to your E1 Card == |
| 25 | 1 | dexter | |
| 26 | 9 | dexter | FIXME |
| 27 | 1 | dexter | |
| 28 | 9 | dexter | == Perform the calibration procedure == |
| 29 | The calibration process takes some time. |
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| 31 | * Connect the HFC-S Card to the S0 line. |
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| 33 | 9 | dexter | * Configure your BTS from standalone to E1 locked and wait about 1 hour to ensure that the calibration takes place on a system that is well warmed up. |
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| 35 | 9 | dexter | * Add type=0x00800 to the modprobe hfcmulti ... commandline |
| 36 | 10 | dexter | |
| 37 | 9 | dexter | * start isdynsync |
| 38 | 10 | dexter | |
| 39 | 9 | dexter | * start bsc_hack |
| 40 | 10 | dexter | |
| 41 | 9 | dexter | * use bs11_config to monitor the calibration process. |
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| 43 | Note: It is highly recommended to measure the signals at C4IO and F0IO to make sure that the signal is present! |
