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well the dongle made a 90kb file when I first plugged it in, the blue light is flashing, but nothing else is happening.
I'll try replugging it now it has a fix.
Nothing obvious, think I'll have some lunch and try again later.
on the battery thing, the dongle is enough to keep my powerbank on. I know the Pi has turned off because it's no longer on samba. but the dongle is still powered holding the battery on.
well the dongle appears to be working now it's up to 92kb and counting. But still nothing from the module.
Going back to the board now
Don't know what's happening with the module now, but it's stopped saving the baud rate, reverted back to 9600 overnight, and now won't hold it through a brief disconnect reconnect. I'm sure I'm getting it right now. save PRT, save receiver, save CFG.
Thought maybe I'd knocked the battery loose but that looks OK, I'll put the meter on it tomorrow and check.
Not seeing what's happening with the Pi and the dongle is ok when everything works fine, but it's obviously no good when trying out new things. I've gotten the 2.13 in e-ink HAT from Waveshare (https://www.amazon.com/gp/product/B071S8HT76/) to work. So far, it only shows status messages, not speed, but that will come. Not sure if you can get it for a reasonable price in Australia. Also, it fits best to a Pi Zero W (the one with the header).
I looked at the GPS module that I have, the exact same type, and there is indeed a battery. It measures at 1.028 volts, which is a tad low, although mine seems to retain its config. The battery can be measure by using a multimeter on the top surface and the corner on the pcb where its mounted.
(Edit: Maybe its not a battery after all. I ran the GPS up and after disconnecting the voltage on the 'battery' it is now around 2.4v. It could be a capacitor. There are certainly diagrams online that show a capacitor on the V_BCKP pin. Decrepit, your module looks slightly different in that the metal tag that holds down the battery/capacitor is aligned differently. There are three triangular tabs under the battery and the tab on mine is soldered to the one furtherest away from the gps chip closest to the UART connection point. You can measure the voltage on the one that points towards the ublox chip or the one that is on the outside of the board. Yours looks like it is soldered at that tab that is pointing to the ublox chip. I wonder if this is a manufacturing fault and its soldered to the wrong place?)
In the config CFG screen of U-centre, it automatically highlights the 0-BBR and 1-Flash entries when you go to save the config, so it implies that it saves to flash as well. I don't know when it uses the flash config versus the ram memory.
Maybe these boards are old stock and the batteries are on the way out? The same board looks to support previous generations of GPS chip, so maybe that's the case?
I think if writing scripts for these it would be good to initialise them every time with the default baudrate and then change the baudrate straightaway, just in case the config is lost or a new module is used.
BTW - I probably was wrong thinking that seeing only 32 channels in ucenter is a sign of a fake ublox 8, according to this: portal.u-blox.com/s/
I got some windsurfing data today with the Pi Zero and the GPYes dongle. The good news is that is worked ok. The bad news is that the accuracy was not as good as expected, with typical errors of +- 0.8 knots; I expected below 0.5. So I did some playing around with different positions of the GPS unit relative to the Pi; here's a plot of the accuracy estimates for 4 different configurations:
For the first ~300 points, the GPS was about a meter away from the Pi (on a USB extension cord). For the second 300 points, it was right next to it; then right on top of the e-paper display; and finally on the battery, next to the Pi and a bit below the display. The average error estimate was about 3 x higher for the last configuration - which is unfortunate, because that's what I used. So the best positioning of the GPS will need some more research.
I stumbled across this when looking at the GPS information:
rtklibexplorer.wordpress.com/2016/11/04/pi-zero-based-gps-data-logger/
This looks like a Rpi Zero using the serial interface direct to the GPS module instead of using USB and a converter. It looks like a better approach if all you have is serial GPS modules.
Checked my battery/capacitor at 0.2mv between the one nearest the chip and the one nearest the terminals. after it's been sitting all night.
checking between ground and pin 22 on the chip I get 0.1mv.
The ublox data sheet says an m6 pin 22 is normally tied to ground and when converting from a 6 to an 8, this is OK to stay that way.
So connecting anything there indicates some thing different going on.
When plugged in I get 3.25v disconnect drops to virtual 0.
So I'd better investigate the connections a bit further.
Can't remember where this came from, I think it's Steven's or maybe from a sellers site?
It has the same chip as mine, but the battery/cap is then other way around. If it's not a polarised cap that should be OK.
But the cct shows it as a battery.
Guess I'll just have to disconnect it and see if I can figure it out.
well here it is.
Looks like a 3.3v battery to me and thanks formula for spotting this, soldered in the wrong way around, which looks to have shorted it out.
The multi meter also says it's not wired the same as the schematic shows. The big pad closest to the chip is ground, but the connection closest to the mounting hole doesn't go directly to pin 22, there's a 1k resistor in between, so the battery is on the other side of the resistor
So the question is now, can I find another battery?
More later.
My google search found a rechargeable button battery, hadn't thought of that but it makes good sense. Probably doesn't do much harm to short out a rechargeable, so I've soldered it back in the correct way round, and wonders of wonders, it's slowly charging up. So I'll let it sit for a while and see if it works any better.
well looks like I fixed that and now nothing works @##@$%%^^^.
Am I getting some sort of message here?
now the Pi isn't seeing the dongle or the module.
This ancient brain isn't a help either, took me ages to wake up to the fact, I have to modify /etc/rc.local every time I swap them over.
And then much later, that you have to reboot for this to have any effect!
So now the Pi is seeing the module but only makes an 80byte file then shuts down. I can no longer get the module to output any data, with any baud rate with both receiver and port set the same, and it says I have "0" channels even though the green light is flashing. I can see my adjustments going in and getting acknowledged, so there is communication just no data.
So have I fried something with all my probing? I wasn't wearing my antistatic wrist strap, but I'm standing on slate tiles on concrete, in bear feet. Or have I set something wrong no that I can actually save something?
And The dongle seems to be working fine in u-center but isn't starting a file in the Pi.
Think I'll concentrate on something else for a while, until the smaller 2200mah battery and an otter box arrive.
My second GPS module had the capacitor go up to 2.75 volts when running and then down to 2.5 once powered down. From a 'never-used' 0.1mv, I think we can assume its a cap.
The 0.07 farads is why they are called 'super' capacitors.
Its not a bad choice in this application as it will keep the ram powered up for long enough, but after a while it loses its config and satellite info.
That's bad luck to get a module that has had the cap installed the wrong way.
Now that you have removed the cap, make sure you start from the default baudrate of 9600.
Good luck.
