Thanks. This is more subtle than I thought. I have always assumed that the board’s pins are 5v tolerant and the on board regulator protects the actual u-blox chip.
But the GPS TX pin wouldn’t go thru the regulator would it?
James is doing it the same way so his comments will be helpful.
These are the voltages I measure on the converter’s pins. It’s plugged into the laptop’s USB port and nothing is connected and no jumper.
pin volt
GND -
RXD 3.6
TXD 3.6
3V3 3.4
VCC 3.6
5V 5.1
With the jumper across the 3V3 and VCC pins they are at 3.6V.
The RX & TX pins at 3.6V – this is to be expected, is it?
You have confused me a little
The bit in question here is “5v pin to its 3.3v pin”
and here it is “across the 3V3 and VCC pins”
Just where is this jumper supposed to connect. I am guessing here but it looks like this jumper could set VCC to either 3.3V or 5V. If that is the case I would set it to 3.3V to be on the safe side. Also you would not need the logic level converter I don’t think.
Maybe someone a little more up to date on this TTL/USB converter might like to comment.
Bu the way what is the make and model of this thing. That would possibly help.
Cheers Bob
Sorry, my clumsy mistake. The jumper can’t connect those two. The pinout is:
GND RXD TXD 3V3 VCC 5V
You’re thinking seems right – it connects either 5v or 3v3 to VCC.
So connecting 3v3 to VCC means all data signals (both ways) will be 3.3v?
Shud I take power to the GPS from the VCC or the 5V pin?
Here’s a link to a typical seller of the converter (the “data sheet” is poor):
TTL/USB converter
I think James from Core will be able to advise.
John.
Hi John
That link takes you to a unit that has only 5 TTL side pins. You describe 6. Obviously not the same one.
The data sheet is for the chip itself and seems to have an on chip regulator and is USB bus powered which will be 5V. Where the actual board pin connections come from I have no idea.
Someone who is more familiar with this converter will have to chip in here as I am not familiar with it at all.
Your pic seems to indicate 2 different converters. The EXACT make and model would be good. A link to something that looks like it is worse than useless. Surely there is something printed on it or maybe it is written in Swahili. Might as well be.
Cheers Bob
Don’t do anything rash until you find out more about this thing.
Bob,
That link was the best match I could find. It looks the same as mine from above. I didn’t notice it only had 5 pins. I’ve searched but can’t find the store where I bought mine. I may have ordered the one in the link and received something a little different.
The two converters are identical – I bought two at the time. One has its pins parallel to the board and is installed vertically to the breadboard. The other has its pins at right angles to the board and is inserted parallel to the breadboard. I have removed the plastic sleeve from one. So they look different but are identical functionally.
There is no maker, model or any other info on them. This is not unusual with boards from ebay (cheap ones).
Yes, I’ve become nervous about connecting up a new GPS unit until I have positive knowledge about this voltages issue. I like this process – it’s about KNOWING things are right rather than assuming.
I’ve been looking at tutorials on using these boards with Arduino (which everyone follows to get started). Two things: nobody takes ESD precautions and freely handles the devices, including conducting parts; there’s no discussion of ensuring over voltages are kept away from the Neo chip at the heart of the board. Interesting.
John.
One more step for an identical setup: set them both back to factory default configuration and force a cold start. One possibility for the failure is a corrupted parameter storage. Getting them both to the same configuration would confirm that they are starting from the same point. If you can’t see that the configuration is the same that might indicate where the problem is. That would, of course, require connecting the RX. FWIW I have never had a problem handling GPS modules very casually, including two units (not similar to these) where I had to experiment to find out what the pinout was, and which turned out to work best at 2.5v!
Hi John.
Good thinking. The first thing I would do (this is me, maybe not for everybody) is throw these 2 converters in the waste box and replace them. Replace with units you CAN get information about, Data sheets are all good but they usually only provide info about the chip in use. What you need is info on the unit as a whole which tells you what all the other bits on the board do with a good description of the complete thing.A circuit of the complete thing would be good. Some suppliers provide this, if not on Core site on the native supplier site although Core usually do reproduce this if available. In a nutshell, if not enough info is provided don’t buy it.
Maybe all good in the hobby or what is known as maker world. Unfortunately (or not depending on how you view it) I have been used to the world where equipment is expected to operate for 10, 15, 20 or more years and reliability or the lack of could be life threatening. Believe me this sort of thinking IS NOT ON.
But horses for courses. As for finding historical info, In military and other high reliability (aeronautical for instance) situations every component used has to be traceable right back to the day it was made. In avionics particularly if the same component fails repeatedly out of the same batch that batch is removed from circulation GLOBALLY.
Cheers Bob
EDIT: Referring to the second quote extract. One thing I bet these people don’t mention is how many failures do they have before getting it right, and how many units fail a bit later on.
John.
That does not look much like a static mat it is laying on.
Before you go any further bring up the data sheet for that module and read chapter 6.4
I will say no more on this subject of static.
Cheers Bob
This is a horror story, Bob. It’s basically saying don’t touch the antenna. I’ve touched all of mine many times in different environments. Everyone using these boards would be doing the same. I’ve handled mine while in the car & that can’t be an “ESD protected work area”.
John
In a production factory environment this can be done but is an overkill for the home.
In reality it is not that hard. The trick is to get your body and the equipment you are trying to protect at the same potential so no discharge takes place when you touch anything. It does not have to be “Ground” as such as long as everything is the same.
A simple static mat and a wrist strap attached to it will do nicely. Mine is 55cm X 30cm and is quite big enough for home use and effective (I think, with this sort of thing you will never know). For a few dollars cheap insurance.
Some people are saying I have done this and I haven’t taken any precautions and this person has done this and so on. That is fine but the fact is you seem to be having a major problem. It may not be static but it is a possibility and unless you do something about it you cannot discount this as a cause. If it really is static it may even be you. You must have seen it countless times when some people get out of a car they experience a feelable shock as they step out while still holding the door. Some people are affected more than others and if bad enough can even produce a spark. What do you think that can do to sensitive electronics.
Enough said. Up to you now.
Cheers Bob
The part that is unavoidable to touch is that brass plug at the end of the antenna cable cos it has to be pushed into the tiny socket on the board. That would be the ground conductor, the inner conductor would be the RF. So is it safe to touch that outer conductor?
Is it good enuf precaution to touch some large metal object before handling these devices? Like a car door – in summer you can certainly feel the static discharge when touching a car door.
Read my reply just now. Nothing is safe if the potential between your body and the device you are working on is high enough. The spark I mentioned above to the car door could be between 5 and 10kV.
NO
Cheers Bob
Okay, it’s the potential difference b/w me & the part that matters. Got it.
So with an anti static mat, you have a strap to your wrist. How do you get the boards to the same potential as yourself? Do you need to deliberately touch their pins to the mat?
I suspect my problem is experienced by others, but not everyone is that interested in resolving it. The tutorials are usually done at the workbench and not using a GPS in a useful way. There’s a lot of handling required to build a practical package. But if you build a package without damaging the unit it will be well protected from then on. So my speedo worked for more than 12 months and it failed when I removed the GPS module to do some exploring.
I’m confident I’m making progress with this issue, so thank you for your help.
John.
YES that is it exactly.
Would probably be a good idea. Can not do any harm.
The fact that they are on the mat is OK as when you pick it up everything will be at the same potential.
Your soldering iron may be a potential problem also. Most modern soldering irons are marketed as static resistant which usually means that there is a connection from the iron body to some sort of ground point somewhere. If you have a point on your iron that looks as if it should be grounded connect this to the mat. If you have any doubt connect a wire from the metal iron body to the mat with a croc clip or similar.
I know this looks like an overkill but the fact is YOU DO HAVE A PROBLEM and need to cover all bases until you can establish what that problem is. If you go in half way again and the same thing happens you will never know.
Cheers Bob
I don’t suppose you can remember exactly what you did. It could be important.
Hi John,
While it likely wouldn’t make too much of a difference, this is the USB to serial converter I used:
It has 3.3V logic, which would help, but I only used the TX pin on the GPS module, so it shouldn’t make too much of a difference as it’s 5V tolerant.
Occasionally, one of the NEO-6M modules will fail, and we will cover that through warranty, but we also want to see your project back on track, and to work out what’s killing them so the cycle doesn’t repeat.
Keen to get to the bottom of this!
-James
Bob,
I ordered a mat and wrist strap the other day. I’m not going to work on this new unit until I get them. You’re right – I need to eliminate as many factors as I can.
Not exactly, but I was playing around with different antennas. I think it emphasises that while the GPS unit is housed in a project box it is safe from my handling.
Hi James.
Some things I would recommend to anyone using this type of GPS board & antenna:
. use ESD precautions
. read the Neo advice on ESD (ch 6.4 of the tech spec document)
. solder the can of the antenna to the underside of the GPS board before using it; solder all four corners.
. with no power connected, attach the tiny IPEX cable socket to the plug on the GPS board ensuring no shorting of the conductors (delicate work)
. cover the IPEX connection with a blob of hot melt glue (to insulate it & prevent its removal)
. never remove the antenna from the GPS board – view it as a permanent integral component of the GPS module
. if you do need to remove the cable connector, do not use a tool like pliers; use fingernails & pull firmly at right angles to the board; and always with no power connected
. never connect the antenna with power connected
. now solder in the header pins
. cover the header pins with something that will insulate them from fingers
Do you have any thoughts on those recommendations?
John.
Late edit:
Don’t detach the plug from its receptacle by using fingernails. That can still apply too much force or applied in the wrong direction to pull the receptacle out of the board. Use angled tweezers as shown in post # 97.
John
Don’t forget your soldering iron.
In that screen shot you posted re section 6.4 of the data sheet soldering iron precautions are mentioned at least twice.
You didn’t by any chance start using a different soldering iron when you opened your unit and these failures started did you.
Just clutching at another obscure straw.
Cheers Bob
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