You are being more helpful to me than you realise. Your methodical approach is just what I need.
You might like to get one of these modules. The underlying technology and maths of GPS is over my head. These modules just hand all the navigational data to you on a plate – no computations by the user are needed.
The static issue is a nagging worry. I don’t take any precautions.
My intention with the latest purchase was to make a “gold standard” setup. If I have a good receiver and good antenna and keep them protected I might be able to diagnose faults with my working unit more readily.
I doubt I’ll discover what caused them to fail. The outcome of this exercise might be a set of best practice guidelines. I’m thinking:
always power off before connecting or disconnecting antenna (avoids shorts)
do not install a pin to the RX via (5V cannot get to the RX if there is no pin)
use anti static practices
insulate the board’s pins at the top (I naturally press on these with fingers when inserting the board into header)
This could be more of a worry than you realise. I noted that the data sheet for the module emphasises in very bold type that this device is ESD sensitive. Does this in 2 places I think from memory. In other words they are warning the user (those that read the data sheets anyway) of this possibility. Also called covering your whatsit in case of any static damage.
Believe me this problem is very real and quite sneaky. A unit will not necessarily fail straight away but wait some time as any damage is cumulative.
The first thing I would do is get an antistatic mat with wrist strap. Do this before playing around with your new module. Core have a couple but either quite small (A4 size) or pretty large (600X1800). Jaycar have a more manageable size (600 x 600). Stock code TH1776. Mine is a handy 550 x 300, Jaycar brand but seem to be no longer stocked. I have had it for a very long time.
This mat does not have to be “Earthed” as such. All OK as long as everything is at the same potential. One of the last big projects I worked on had the equipment room and operations room lined with copper. YES the whole room and ceiling. Windows and all screened with metallic screening. This was referred to as an “equipotential plane” to which everything was tied or “earthed” to. Did not have to be actual “Earth”.
Your list should keep you out of trouble nicely. Beware your soldering iron too. If suspect clip an earth wire to it and connect to your anti static mat (I am assuming you will have one). Keep everything on this mat until you box it up and keep it away from fingers.
Don’t assume the equipment has to be turned on to sustain damage. Static damage does not care if it is on or off.
Cheers Bob
EDIT: Static mat. There a some locally supplied on Ebay. I note one the same size as mine 55 X 30 and another 100 X 50. Search “Anti static mat”
I can’t quite re-create that behaviour. If I do a cold start through u-center I get RMC, GLL and GGA sentences every thirty seconds, properly populated, but with no indication of any satellite reception. So I assume it has retained position and time data through the cold start. That would be similar to your log if your device had no stored data, except for the timing, and the fact that your device seems to be cycling through the satellite numbers. I don’t see that activity at all. That raises the possibility that the problem is a corrupted backup configuration and it is trying to start with invalid settings. I would look through all the configuration options to see what might affect startup. For instance, you could save the current config (CFG) and then revert to default config and do a cold start. Also, you could set set the antenna options (ANT) for short circuit recovery and open circuit detection, just in case there is an issue with the antenna.,
Jeff,
I’m used to the default being the six sentences every second as in my log. The GSV sentence is most important for me at the moment as it tells me what sats, if any, are being received.
If your update rate is 30 sec then won’t your positional data change only every 30 secs?
You can turn sentences on/off and change the update rate thru u-center. That means sending data to the Neo and that shud be at 3.3v not 5v.
It would be great if my problem lies in the config status. I might be able to reset it to default. I don’t know about the ANT short circuit recovery – where can I read up on that, please? Is it covered in the u-center guide?
The details I reported are the default, as this should be the same as you are seeing for the same default. If it isn’t then that might provide a clue to the source of the problem. There is no satellite data being received in this state (as appears to be the case for your receiver), so the update rate is irrelevant. I can reposition the antenna to get updates, and set the update rate to whatever I want, but that’s of no significance for your problem.
This is odd. I decided to see what happens if I provide a non-functioning antenna, and the device would not transmit at all. I managed to get it working by removing the logic level converter and doing receive only. Perhaps the logic level converter failed, or the device couldn’t drive it for some reason, but it is possible that the UART is extremely sensitive to load.
With a partially functioning antenna I got results somewhat similar to yours - GPL, GSA, GSV and RMC with no data. But at no time did it try to cycle through satellite numbers, and even that result didn’t last long, as it soon picked up a satellite immediately overhead.
The antenna was from a WiFi base station which is far too long and should be very inefficient. That it works indicates that the GPS RF section is very capable.
I’ve used a simple length of wire and had good results.
Today I tried to use a 5v/3.3v logic level converter for the first time. I connected 5v to the HV side and 3.3v to the LV side. I measure 5v on all four channels on the HV side and 3.3v on all the channels on the LV side (without any other connections). That doesn’t seem right.
I put the converter aside and connected the PC to the GPS RX pin without stepping down to 3.3v. The GPS board isn’t working so I’m not worrying about damage.
I can send config commands, like change the update rate. Couldn’t work out how to switch individual sentences on and off.
I found the option dealing with ANT short circuit recovery but I don’t understand how to use it.
That’s how cumulative damage occurs. Nothing might fail now but sometime down the track something WILL fail. Might have nothing to do with what is happening at that time and that is what makes it so difficult to pinpoint the actual cause.
Cheers Bob
Yep, I get that, Bob. I won’t do this with a new unit. I don’t expect to get useful performance from this particular unit again, so it’s not a real loss if it does get damaged this way. Thanks.
I find your problem quite curious. I have numerous NEO-6 modules, I have powered them from a 5V wall wart, a 7805 voltage regulator, a car USB charger, and a buck converter. None of them failed. I have one strapped to a rafter with an active antenna with a 3m lead on the roof. I was worried that this would be taken out by a thunderstorm but it’s worked fine for 6 months. I’ve taken the data straight into a PIC processor, into a TTL to USB converter (FT232), into a TTL to RS232 converter (MAX232) and into a line driver (UA9638). No problems with any of these. I have never connected the RX line to talk to the module, only use the TX and 1pps signals. The default NMEA data is OK for my use. And I’ve not taken any static precautions, assuming (probably erroneously) that as they are on a breakout board there would be components to look after static. I’ve also soldered directly to pins to get at the 1pps signal, some boards don’t break that out. I think the oldest module has been running continuously for over 6 years.
I agree with the precautions that others mention, but given my cavalier approach you would think at least one module would fail. So I’m thinking there’s something about your situation that hasn’t been discovered. Someone running a powerful transmitter nearby? A faulty microwave oven? Something putting spikes on your power lines? Frustrating I’m sure.
Hi Alan
Static damage is just one of the many causes that comes to mind. It may be that John’s environment is not very static friendly. Even down to the carpet on the floor. There has to be a reason why every new device he tries fails in much the same manner. Could be anything really even an incorrect connection he keeps repeating. If, as in your situation you box everything up and put it in places like the roof and don’t touch it again, in 99% of cases you will get away without any static prevention but as I said there WILL be a reason and static is only one of the possibles. I can’t believe that every unit is faulty, there must be thousands i use.
Definitely must agree. Like I said John’s problem is likely to be an environmental one.
But it still does not do any harm to take some static precautions.
Cheers Bob
Good point. No wonder you smiled.
Still it is not really in a position where you can easily handle (with your hot fingers) it on a regular basis.
Cheers Bob
A setup like Alan’s makes a good “standard”. With a good receiver, antenna, power supply and wiring and a good location, you can swap out parts of a non-producing system to see which component is not working.
Also allows you to monitor the speed of your home. I once clocked mine at 120 kph.
There all good thoughts, Alan, thanks. I got this behaviour at two locations 400km apart. If it was interference, wouldn’t I still see some genuine sat data rather than a total blackout?
This sounds dumb, but I have to ask. You are aware that the center pin of the antenna connector on the GPS module is powered (for the active antenna) so attaching something which is a DC short is bad news. On most units the power is delivered through a 22Ω resistor to protect against an accidental brief short, and an inductor to block the RF. The RF receive goes straight into the NEO chip so it presumably has an internal cap to block the DC. You talked of using a WiFi antenna and ‘a bit of wire’. These may work for a while but if they are a DC short it may draw too much current causing something to eventually fail. This is clutching at straws.
This is a sample circuit. I’m guessing this is very similar to the one you have. There’s another common one with an extra RF amplifier for an onboard patch antenna (which isn’t powered).
