kalibrate-rtl

calibrate.py

#!/bin/env python3
import subprocess
import re
from functools import reduce
import sys
import argparse

def get_channels(band="GSM900", timeout=60):
    output = subprocess.check_output(['./kal', '-s', band], timeout=timeout)
    match = re.finditer('chan: (?P<channel>[\d]+) \(.*\) power: (?P<power>[\d.]+)', str(output))
    return map(
        lambda x: x.groupdict(),
        match
    )

def get_strongest_channel(channels):
    return reduce(
        lambda carry, item: carry if float(item['power']) < float(carry['power']) else item,
        channels
    )

def calibrate(channel_number, timeout=60):
    output = subprocess.check_output(['./kal', '-c', channel_number], timeout=timeout)
    match = re.search('average absolute error: (?P<ppm>[\d.\-]+) ppm', str(output))
    return match.groupdict()['ppm']

parser = argparse.ArgumentParser(description='Get RTLSDR calibration PPM.')
parser.add_argument('band', type=str, nargs='?', help='GSM band to scan', default="GSM900", choices=['GSM850', 'GSM-R', 'GSM900', 'EGSM', 'DCS', 'PCS'])
args = parser.parse_args()

try:
    channels = get_channels(args.band)
    strongest = get_strongest_channel(channels)
    ppm = calibrate(strongest['channel'])
    print(ppm)
    sys.exit(0)
except Exception as e:
    print(e, file=sys.stderr)
    sys.exit(1)

kal

#!/bin/sh
if [[ "$1" == "-s" ]]
then
cat << EOF
Found 1 device(s):
  0:  ezcap USB 2.0 DVB-T/DAB/FM dongle

Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle
Found Rafael Micro R820T tuner
Exact sample rate is: 270833.002142 Hz
kal: Scanning for GSM-850 base stations.
GSM-850:
    chan: 128 (869.2MHz - 3.988kHz) power: 486634.32
    chan: 143 (872.2MHz - 3.760kHz) power: 56331.63

EOF
elif [[ "$1" == "-c" ]]
then
cat << EOF
Found 1 device(s):
  0:  ezcap USB 2.0 DVB-T/DAB/FM dongle

Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle
Found Rafael Micro R820T tuner
Exact sample rate is: 270833.002142 Hz
kal: Calculating clock frequency offset.
Using GSM-850 channel 128 (869.2MHz)
average     [min, max]  (range, stddev)
- 4.093kHz      [-4102, -4083]  (20, 5.314593)
overruns: 0
not found: 0
average absolute error: 4.709 ppm

EOF
else
cat << EOF
kalibrate v0.4.1-rtl, Copyright (c) 2010, Joshua Lackey
modified for use with rtl-sdr devices, Copyright (c) 2012, Steve Markgraf
Usage:
	GSM Base Station Scan:
		kal <-s band indicator> [options]

	Clock Offset Calculation:
		kal <-f frequency | -c channel> [options]

Where options are:
	-s	band to scan (GSM850, GSM-R, GSM900, EGSM, DCS, PCS)
	-f	frequency of nearby GSM base station
	-c	channel of nearby GSM base station
	-b	band indicator (GSM850, GSM-R, GSM900, EGSM, DCS, PCS)
	-g	gain in dB
	-d	rtl-sdr device index
	-e	initial frequency error in ppm
	-E	manual frequency offset in hz
	-v	verbose
	-D	enable debug messages
	-h	help
EOF
fi