eg25-gps-init: improve docs
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@ -7,11 +7,20 @@
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#
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#
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# this script downloads assisted GPS (AGPS) data via the system's default gateway (i.e. WiFi)
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# this script downloads assisted GPS (AGPS) data via the system's default gateway (i.e. WiFi)
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# and shares that with the modem. this quickens the process of acquiring a GPS fix.
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# and shares that with the modem. this quickens the process of acquiring a GPS fix.
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# even with AGPS, an indoor fix is generally not possible (though i have seen the receiver
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# locate a _single_ satellite from indoors -- not enough for a fix).
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# even an outdoor fix within a suburban setting may take 10 minutes.
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#
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#
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# expects to run on megi's kernel, with `CONFIG_MODEM_POWER=y`
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# this script expects to run on megi's kernel, with `CONFIG_MODEM_POWER=y`.
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#
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# EXPECTATIONS/TIPS:
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# - with the right environment, you may get a GPS fix in < 30s.
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# - indoors, you shouldn't expect to *ever* get a cold-start GPS fix.
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# - maybe you'll track 1 satellite if lucky: enough to receive GPS time but not for a GPS fix.
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# - get a fix outdoors, then walk indoors: GPS is smart enough to maintain a spotty fix.
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# - outdoors in suburbia, a fix might take 10-20 minutes.
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# - i have better luck *placing my phone on the roof of my car* than holding it in the air with my hand.
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# - maybe a big metal plate opposite the sky acts as a dish/antenna?
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# - in Seattle, i track several GLONASS and GPS sats: about an even split.
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# - the GPS sats have better SNR.
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# - modem seems to not show any BeiDou or Galileo sats even if i enable them.
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#
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#
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# eg25 modem/GPS docs:
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# eg25 modem/GPS docs:
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# [GNSS-AP-Note]: https://wiki.pine64.org/images/0/09/Quectel_EC2x%26EG9x%26EG2x-G%26EM05_Series_GNSS_Application_Note_V1.3.pdf
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# [GNSS-AP-Note]: https://wiki.pine64.org/images/0/09/Quectel_EC2x%26EG9x%26EG2x-G%26EM05_Series_GNSS_Application_Note_V1.3.pdf
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@ -36,7 +45,8 @@ import time
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POWER_ENDPOINT = "/sys/class/modem-power/modem-power/device/powered"
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POWER_ENDPOINT = "/sys/class/modem-power/modem-power/device/powered"
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# GNSS-AP-Note 1.4:
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# GNSS-AP-Note 1.4:
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# also at xtrapath5 and xtrapath6 subdomains
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# also at xtrapath5 and xtrapath6 subdomains.
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# the AGPS data here is an almanac good for 7 days.
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AGPS_DATA_URI_BASE = "https://xtrapath4.izatcloud.net"
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AGPS_DATA_URI_BASE = "https://xtrapath4.izatcloud.net"
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class AgpsDataVariant:
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class AgpsDataVariant:
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