I have the breakout board connected via USB and the activity light blinks when I send commands but I have never received any response. I’m using 115000 N81 and have tried multiple cables and both a Mac and a PC.
The status light has also never shown a GPS lock - it just flashes red. I have double checked that the antennas are plugged in correctly.
I feel like I’m missing something simple or potentially the board is defective.
Hi @haugenmarine,
What software are you using to communicate with the modem? Are you using our GUI? Or have you written your own code? (In which case, are you formatting each message correctly - with a checksum?)
Re: the GPS lock: have you taken the system outside, so it has a clear view of the sky? If you are using the Molex u.FL adhesive antenna, it needs to be pointing away from the modem. You’ll get no signal if it is positioned over or under the Swarm antenna ground plane - or another ground (including the modem itself). A photo would help.
Best wishes,
Paul
Thanks for the quick reply. I’m using your gui software on windows 11. I’ve also tried numerous serial apps on windows and mac and multiple cables. All the same; no response at all from the modem. The rx light flashes so there is some sort of connection. I’ve attached a screenshot. This part works perfectly for everyone else so not sure what else to try at this point!
As far as the GPS it works much better outside - I guess it’s the added interference from the rest of the hardware being so close? Otherwise that would be concerning that it can’t grab a signal.
I can also confirm that the RX light on the breakout board flickers with activity when I send data but the TX light never lights up at all.
It doesn’t seem to respond to any commands, e.g. sending the restart device command does nothing even though the RX light flickers with activity.
Hi,
Many thanks for the detailed information - and apologies for the inconvenience. It does sound like you have either a faulty SparkX board, or a faulty modem. The modems arrive at SparkFun pre-tested and we test our boards during production - checking both the TX and RX signals. However, a fault may have developed.
Do you have access to a multimeter with pointed probes? If you do, please tell me, and I will send images showing how you can check the continuity of the tracks from the CH340 USB interface chip to the modem connector. (For safety, you will need to disconnect the board and remove the modem from the board first.)
If you bought the kit directly from SparkFun, you can return it here: https://www.sparkfun.com/returns
If you bought it from a distributor, you will need to return it to them.
Apologies again for the inconvenience.
Very best wishes,
Paul
I do have a decent meter with probes that might work, would be curious to check it out.
I started a return since I bought it directly from SparkFun.
Thanks for your help
Hi,
Apologies. I should have thought of this sooner. Are the two jumper links next to the RXI and TXO pins still closed? Those need to be closed if you want to use USB. If you have opened them - so you can connect RXI and TXO to an Arduino board - you will need to close them again. Please see:
https://learn.sparkfun.com/tutorials/sa … akout-pins
If you still want to check the track continuity, you need to check that there is continuity from:
CH340 Pin 8 to the M.2 connector Pin 11
CH340 Pin 9 to the M.2 connector Pin 13
Please see the attached three images for more details. For safety, you should remove the modem first: disconnect the board; unscrew the two M2.5 screws; the modem will lift up at an angle; remove the modem; then test for continuity.
I hope this helps,
Paul
PCB:
Schematic:
Photo:
I didn’t open the tx/rx jumpers and I checked them they are still closed.
There is continuity between the pairs on the board as you indicated.
Remember that even though RX lights up the device never responds to the commands (such as restart).
I submitted the RMA but haven’t heard back.
Thank you so much for your detailed help it would have made all the difference if I couldn’t get a replacement.
Hayes
I get this week my M138 Modem.
today I test it, but I don’t get any message from the serial port.
The red led from the Modul is off after 1-2 Min → GPS shoud be fixed…
I use SwarmM138GUI to send commands to the modul.
If I send a command, I see the small right led flashing, but never the left led.
Tomorrow I like to check the jumpers and die signals on the breakout pins…
I have the exact same issue, just got my kit and it’s only blinking on the orangeish led when I press send from the GUI (tested on two different computers, one Win11 and one Linux). I get a GPS fix and all, but I’m assuming that shouldn’t be neccessary for serial communication.
I can’t immediately test for continuity, is there a known problem or quick fix for this?
Hi @grisu @AstarothPoD,
I haven’t seen this issue personally, but it appears that there are now three of you that have the exact same problem.
Could you both please let me know if you have the red SparkFun breakout board - or the earlier black SparkX version?
Apologies for the inconvenience,
Paul
Hi! It’s the red one.
OK - thanks. I will talk to my colleagues on Monday/Tuesday and we’ll sort out a solution for you.
Apologies again for the inconvenience,
Paul
PaulZC:
Could you both please let me know if you have the red SparkFun breakout board - or the earlier black SparkX version?
The red one…
Thank you,
I will talk to my colleagues and we will work out a solution for you.
Apologies for the inconvenience,
Paul
grisu:
I get this week my M138 Modem.today I test it, but I don’t get any message from the serial port.
The red led from the Modul is off after 1-2 Min → GPS shoud be fixed…
I use SwarmM138GUI to send commands to the modul.
If I send a command, I see the small right led flashing, but never the left led.
Tomorrow I like to check the jumpers and die signals on the breakout pins…
I check the successfull:
CH340 Pin 8 to the M.2 connector Pin 11
CH340 Pin 9 to the M.2 connector Pin 13
The levels of the breakout pins:
Vin : 0V
GPIO1: 3.3V
Tx/Rx: 0V
RXI: 5.1 V
CH340 TXO: 5.1V
TXO: 5.1V
CH40 RXI: 5.1V
If I send a command per USB:
I see the bits on RXI und ch340 TXO the same bits… (see pic)
On TXO and ch40 RXI I don’t see any level change.
It seems like we are at the point where we need to boards back for evaluation.
Anyone here who is experiencing issues with the Swarm M138 product please fill out a return ticket and we will work on figuring out what the issue is once the unit arrives.
https://www.sparkfun.com/returns
Thanks!
TS-John:
It seems like we are at the point where we need to boards back for evaluation.Anyone here who is experiencing issues with the Swarm M138 product please fill out a return ticket and we will work on figuring out what the issue is once the unit arrives.
Done
grisu:
TS-John:
It seems like we are at the point where we need to boards back for evaluation.Anyone here who is experiencing issues with the Swarm M138 product please fill out a return ticket and we will work on figuring out what the issue is once the unit arrives.
Done
But I don’t get any response jet? Can you help?
Hi @haugenmarine @grisu @AstarothPoD,
I have some information which I hope will help:
I am testing the breakout board and modem returned by @haugenmarine. When I received it, the modem and breakout were separate inside the box. I inserted the modem into the breakout board, secured it with the screws, connected the GPS antenna, connected it to my Windows PC via USB, opened the Swarm GUI and I was able to send commands and get the correct responses. In summary, it appears to be working perfectly…
However, after some trial and error, I am able to insert the modem into the breakout in such a way that: the modem receives power (the modem LEDs illuminate normally); but where serial communication is not possible. I think I have managed to insert it in a position where either the TX or RX pin - or both - are not connected.
The solution is to remove the screws, remove and re-insert the modem, taking care to insert it fully into the socket, and then secure it with the screws.
I will try some more tests and will report again here.
Apologies for the inconvenience and I hope this helps to solve your issue.
Best wishes,
Paul
