Reply To: Receiving No Data

[Mark Williams]

Sorry if it wasn’t clear.  ill make sure that page gets updated.

If you connect via QWIIC connector only, you would only be able to access the GPS module via i2c (you would need to solder a couple of jumpers on the back to enable this function).   This means you would not be able to use GPSD as GSPD relies on serial.  We are trying to come up with a way to make it work with GPSD via i2c.

You can however, get lon,lat, speed, etc.. via i2c using

 
Here is some python code I have been playing around with;

import time
import json
import smbus
import logging 
BUS = None
address = 0x42
gpsReadInterval = 0.1
LOG = logging.getLogger()
GPSDAT = {
    'strType': None,
    'fixTime': None,
    'lat': None,
    'latDir': None,
    'lon': None,
    'lonDir': None,
    'fixQual': None,
    'numSat': None,
    'horDil': None,
    'alt': None,
    'altUnit': None,
    'galt': None,
    'galtUnit': None,
    'DPGS_updt': None,
    'DPGS_ID': None
}
def connectBus():
    global BUS
    BUS = smbus.SMBus(1)
def parseResponse(gpsLine):
    global lastLocation
    gpsChars = ''.join(chr(c) for c in gpsLine)
    if "*" not in gpsChars:
        return False
    gpsStr, chkSum = gpsChars.split('*')    
    gpsComponents = gpsStr.split(',')
    gpsStart = gpsComponents[0]
    if (gpsStart == "$GNGGA"):
        chkVal = 0
        for ch in gpsStr[1:]: # Remove the $
            chkVal ^= ord(ch)
        if (chkVal == int(chkSum, 16)):
            '''for i, k in enumerate(
                ['strType', 'fixTime', 
                'lat', 'latDir', 'lon', 'lonDir',
                'fixQual', 'numSat', 'horDil', 
                'alt', 'altUnit', 'galt', 'galtUnit',
                'DPGS_updt', 'DPGS_ID']):
                GPSDAT[k] = gpsComponents'''
            print gpsChars
            #print json.dumps(GPSDAT, indent=2)
def readGPS():
    c = None
    response = []
    try:
        while True: # Newline, or bad char.
            c = BUS.read_byte(address)
            if c == 255:
                return False
            elif c == 10:
                break
            else:
                response.append(c)
        parseResponse(response)
    except IOError:
        time.sleep(0.5)
        connectBus()
    except Exception, e:
        print e
        LOG.error(e)
connectBus()
while True:
    readGPS()
    time.sleep(gpsReadInterval)

Mark --OzzMaker.com --