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Proof of concept AGPS data loading for PinePhone
#!/usr/bin/python3
#
# load_agps_data
#
# proof of concept loading of agps data to quectel modem via AT commands
from datetime import datetime, timezone
import requests
import serial
at_port = '/dev/ttyUSB2' # ttyUSB2 is the command port on mobian - think they renamed via udev on PmOS
agps_url = 'http://xtrapath1.izatcloud.net/xtra.bin'
agps_file = 'RAM:xtra.bin'
def sendCmd(cmdstring):
print(cmdstring)
ser.write(f"{cmdstring}\r\n".encode('ascii'))
res = []
while True:
line = ser.readline()
if (line == b''):
break
else:
res.append(line)
print(res)
return res
def setTime():
now = datetime.utcnow().replace(tzinfo=timezone.utc).strftime('%Y/%m/%d,%H:%M:%S')
return sendCmd(f"AT+QGPSXTRATIME=0,\"{now}\"")
# is ModemManager running? Won't work if it's already got the port
print('open serial port')
ser = serial.Serial(at_port, timeout=1)
print('Check modem will talk to us')
res = sendCmd('AT')
# FIXME - expect response OK - really ought to check this and other responses
## is GPS turned on? If so the later stuff won't work so we'll have to turn it off
print('Is GPS turned on?')
res = sendCmd('AT+QGPS?')
print('Turn off GPS')
res = sendCmd('AT+QGPSEND') # this ought to be sent only if the gps was on...
print('Is AGPS enabled?')
res = sendCmd('AT+QGPSXTRA?')
print('Precautionary enabling of AGPS')
res = sendCmd('AT+QGPSXTRA=1')
print('Is valid AGPS data already loaded?')
res = sendCmd('AT+QGPSXTRADATA?')
# FIXME: check the returned stuff
# actually this check seems unnecessary as the returned value is alway the same
# so doesn't help (and doesn't match the docs)
# fetch http://xtrapath[1-3].izatcloud.net/xtra(2).bin and upload
r = requests.get(agps_url)
#FIXME: check r.status_code before doing anything with the data
print('download status: ', r.status_code)
# precautionary delete of the target file - upload will fail if file name in use
print('delete previous AGPS data file')
res = sendCmd(f"AT+QFDEL=\"{agps_file}\"")
print('upload new AGPS data')
res = sendCmd(f"AT+QFUPL=\"{agps_file}\",{len(r.content)}")
# FIXME: check res == CONNECT and don't send if it's not
ser.write(r.content)
res = []
while True:
line = ser.readline()
if (line == b''):
break
else:
res.append(line)
print(res)
#FIXME: calculate agps file checksum and check that it matches the response
# we'll assume here that local system time is kept accurate either by NTP or
# phone network time, so we don't need to fetch SNTP time
print('set current UTC time using local system time')
res = setTime()
print('set AGPS data to file we uploaded')
res = sendCmd(f"AT+QGPSXTRADATA=\"{agps_file}\"")
print('what does it day about data validity now?')
res = sendCmd('AT+QGPSXTRADATA?')
print('NOTE: it\'s given us the same response as before, despite having new data uploaded')
print('enable gps')
res = sendCmd('AT+QGPS=1')
print('close serial port')
if ser.is_open:
ser.close()
@alastair-dm

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@alastair-dm alastair-dm commented Jul 15, 2020

Tested on Mobian - I think PmOS remaps the tty names in udev rules, and other distros may too. Again depending on distro you may need to stop whatever service is already using the port before running it, and re-enable after. On Mobian this is ModemManager:

#!/bin/sh
#
# stop ModemManager, run python script to upload AGPS data then restart ModemManager

sudo systemctl disable ModemManager.service
sudo systemctl stop ModemManager.service
/home/mobian/load_agps_data.py
sudo systemctl enable ModemManager.service
sudo systemctl start ModemManager.service

Prerequisites - python3 and its requests and serial libraries:
sudo apt install python3 python3-requests python3-serial

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@alastair-dm alastair-dm commented Jul 15, 2020

Also if AGPS is NOT enabled (which it probably won't be to begin with) you'll need to restart the modem after running the script as the setting is only activated on restart. I powered down the phone and removed the battery just to be certain, but but there are probably easier ways.

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@Lin-Admin Lin-Admin commented Oct 1, 2020

This helped to get a fix within a few minutes. I suggest to combine the shell script into the .py script and to add
"mmcli -m 0 --location-enable-gps-nmea" at the end.

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@alastair-dm alastair-dm commented Oct 1, 2020

That would make it specific to distros using systemd and ModemManager. If you want to use it as the basis for a better script then feel free, but the better fix would be to get it fixed in the upstream ModemManager, oFono or whatever.

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@beckmi beckmi commented Feb 18, 2021

  1. agps_url should be 'http://xtrapath1.izatcloud.net/xtra2.bin' that changed the date for me to '2001/07/05,06:00:00'
  2. line 82 should be changed to sendCmd('AT+QGPSXTRA=0') otherwise the module unnecessarily drains the battery
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@alastair-dm alastair-dm commented Feb 19, 2021

  1. Any reasoning behind that choice of URL, or just trial and error? I picked the first from Quectel_EC25EC21_GNSS_AT_Commands_Manual_V1.1.pdf but apparently there are others that aren't listed there. Qualcomm customers seem to have been having problems on and off since the gps epoch rollover last October, and there are hints it may depend on firmware version: https://developer.qualcomm.com/comment/17055 More research needed on this, but it might explain why some people have been having more difficulty than others.
  2. It's proof of concept - I wanted it spewing NMEA data so it was easy to see if it was working. It's far from a proper tool to be using for a variety of reasons. If you're worried about power then you need something like the gpsd hook to turn it on and off on demand anyway. ModemManager needs support adding so we don't need a separate tool, and to allow gps to be turned on when there's no SIM present since the hardware supports that. I'm not clear on how oFono handles this sort of thing.
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@beckmi beckmi commented Feb 19, 2021

  1. Simply trial and error.
  2. Yes – I know. It was just a little surprising for me to see that the battery was discharged within a day of testing, instead of five days ...

I think there still is a lot to do. The device even sometimes changes state to unavailable for no apparent reason.
Nevertheless nice thing to play with :)

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