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SlashDevin / NeoGPS

NMEA and ublox GPS parser for Arduino, configurable to use as few as 10 bytes of RAM
GNU General Public License v3.0
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I2C Input stream #33

Closed bluespider42 closed 7 years ago

bluespider42 commented 7 years ago

I can't find any reference to using an i2c in the documentation or code. Is the feature implemented? if so how should I start?

jamesmayes commented 7 years ago

You should be able to use the Arduino Wire library since it derives from Stream. That's really what the NeoGPS library cares about.

SlashDevin commented 7 years ago

Yes, use the I2C Wire library to obtain bytes from the device. Then pass those bytes to NeoGPS, through the Character-Oriented methods. NMEAblink shows how to pass one byte from the serial port (here).

You have to be careful about reading from I2C: it will return 0xFF bytes when no data is available. There is a TXDATA_READY pin you could use. The PPS pin could also be used as a start flag (read until 0xFF appears again). Or just read constantly and skip 0xFF bytes... or just pass everything to gps.decode and let NeoGPS ignore the 0xFF bytes.

bluespider42 commented 7 years ago

SHould I just Wire.requestFrom(0x42, 1) followed by a Wire.read() in a loop or is it better to request more bytes and then continue to read untill 0xFF is returned?

bluespider42 commented 7 years ago

I've found my problem from an earler version of my code (where I was using the UART port) I had a if (fix.valid.location) {..} (after assigning fix = gps.fix() safely) which was never returning true for some reason.

jamesmayes commented 7 years ago

Did you confirm the proper last sentence for your device?

SlashDevin commented 7 years ago

SHould I just Wire.requestFrom(0x42, 1) followed by a Wire.read() in a loop or is it better to request more bytes and then continue to read untill 0xFF is returned?

It depends on your device. Which one are you using? I have never used the DDC (aka I2C) interface of a ublox GPS device, but according to the NEO-6M spec (section 4.3), I would think that reading more than one byte at a time is much more efficient. You can read the registers at 0xFD and 0xFE to get the number of available bytes, if you want.

So many choices! :)

I've found my problem from an earlier version of my code (where I was using the UART port) I had a

fix = gps.fix();
if (fix.valid.location) {..}

which was never returning true for some reason.

Like @jamesmayes said, use NMEAorder.ino to confirm you have chosen the correct LAST_SENTENCE. This is almost always the problem. (0x42 internet points to james!)

bluespider42 commented 7 years ago

Thanks for the help - I making progress now. I hadn't realised that Wire was derived from Stream and using it as such seemed a little counter intuitive to me.