Arduino Nano BLE 33 communication with SIM800L - how to get the GSM module working?

Welcome,

There are plenty of topics on the internet about the SIM800L itself. I, on the other hand, have been sitting, reading and unable to bring the 800L to life for the last 3 days.

What I have:
- Arduino Nano BLE 33 Sense
- Sim800L:
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- Sim800L v2:
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- Mains adapter 12V, 1000 mA
- USB power adapter 5V, 2.4A
- 18650 3.7V rechargeable batteries
- Diodes, resistors, capacitors.

Test code
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On AT it does not respond, on "s" it throws errors, on "c" it says "NO DIAL TONE".

The LED flashes every 0.5s, continuously, no interrupts. I've tried all the suggested connections for these modules, so I'm not giving the current wiring diagram as I've dumbed myself down. I am testing with a Play card. According to the information I've been able to get it 2G should be supported. I've tried moving closer to the window to get a signal, but nothing.

I would appreciate your help, I have to hand in the project in a week .

Hi, thanks for the reply, although I don't quite understand what program upload error you are talking about. I use Visual Studio + vMicro and Visual Code + PlatformIO. I only use the Arduino app itself when I need to isolate a bug quickly. My target program is different, the one I've given is a test one just for the module itself so I don't have to wait for all my other fucks to load.

That test code I gave also loads. Remember that the 33 BLE Sense has a hardwired serial, so the UART may not work on other boards with liba wiring_private.

My board model is exactly this one: https://store.arduino.cc/arduino-nano-33-ble-sense all markings are identical to the manufacturer's picture. The same goes for the GPS modules, they are as in the images I provided. I first had the smaller red one, but thought I might have stoned it and bought myself the blue one, v2 (pictures in the 1st post). I'm struggling with them and can't get them to work. I make no secret of the fact that I'm not an electronics or electrical engineer, I use tutorials and datasheets when it comes to wiring issues, but these modules are giving me fits, probably the only ones I haven't brought to life so far.

Symptoms as in the first post. I don't know what else I can give you to try and solve my problem.

Wizzyz wrote:

I don't know what else I can give you to try and solve my problem.

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Maybe a pic of how you have it connected, especially the power supply. GSM modules are not forgiving of a poor power supply. Once you have verified the power supply you can move on to the code.

So:

Sim800L v2 (blue):
.
Sim800L (red):
.

For v2 I connect it directly to v5 and GDN from the power supply, SIM TX -> RX is at res. 1 kOhm. Here there are symptoms as if there is a problem with the power supply, as the GSM diode blinks 10x, a small pause and again 10x, etc.

For v1 (red) I connect to a power supply independent of the Arduino, a 3.7V battery pack and a GDN. The rest as above. On this module the diode blinks every ~0.6s without interruption, continuously.

I have the power supplies as in the 1st post. I am anxious to get any of these modules working, maybe this v2? I want a simple and concrete solution.

The Nano 33 BLE Sense itself only has a 3.3V output, no 5V, so I am pulling +5V to the SIM800L v2 from a 5V, 2.4A power supply.


P.S. By the way, the Nano 33 Sense is the worst board I have worked with, terribly problematic when it comes to stable operation with the environment.

EDIT: I'll add that I also tried shortening the power wires as much as possible and using a slightly thicker gauge than the standard jumper wire. Didn't help.

A GSM module will not run properly on a contactor. Contact resistances are often several hundred milliohms.
This is what the voltage looks like on the SIM808 modem, which is powered via the contact board when it connects to GPRS.
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These capacitors in the modules are not enough.
After such an event, the modem does not respond to any AT commands or gives errors.

I took this into account, although I had no way of measuring it at home and no equipment. I continued with this after watching a ton of videos where people connect the same modules on the fly and it works for them. I can't quite grasp this. As for the connection itself, is it OK, or is there something better you could suggest?

P.S. I also tried earlier to connect the power supply directly from the PSU to the module, without a contact, and the result was the same. Leaving aside the RX/TX communication issue itself, by connecting the module directly to the 3.7V power supply it never managed to log into the network, it blinks non-stop instead of once/3s.

In some quick experiments, I solder the power supply to the module pins and directly to the module pins I solder e.g. 470uF/6.3V low-impedance 0.008Ω (at TME they have) and then on the power supply side I never had any problems.

Quote:

where people connect the same modules on the "stick" and it works for them

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It depends on how you get on with the contactor.

Master my gold, 200 degrees, some tin and it works. Many thanks! I will be soldering any test power supply from now on. Greetings

EDIT: and how to connect the GDN from the power supply to the one from the Arduino if the power supply is +5V and the Arduino max is 3.3V? Because I have 10k on SIM RX -> TX, and 20k between SIM RX and GDN from the power supply. With this connection something is not hulaing for me communication with this v2 module.

The GND to the arduino can already be routed via contact. GSM modules can consume up to 2A at times, which, with a total resistance of e.g. 0.5, results in a 1V drop. If the arduino draws, say, 50mA, you will have a drop of 25mV, which is manageable.

Once the voltage problem has been resolved, UART communication lies, e.g.

Performance:

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Will only result in a print of the number in the terminal, but no response, such as "NO DIAL TONE"., on AT command the module is silent.

I have directly connected SIM TX -> RX and SIM RX -> TX. When I connect the GDN from the 800L to the Arduino it doesn't even print in the console after executing the above code.

The LED on the 800L module flashes every 3 sec, which according to the doc. indicates that it is logged into the network. Assuming this is OK, where is my error in connecting the arduino <-> 800L communication?

I'm agonising over the subject because I'm terribly time-pressed, and my frustration level at seeing this module is maxed out Thanks.

Wizzyz wrote:

and my level of frustration at seeing this module makes it difficult for me to think

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During the summer with frustration it is easier, the windows are opened, one hand movement and you already have a clean desk .

And which port do you have the console connected to? Maybe show more of this code.

This is what my current connection looks like: .
The program I am running is the one in the 1st post. The simplest one possible. I'm also testing with AiThinker Serial Tool V1.2.3 and there too it doesn't respond to any AT commands.

Am I seeing it correctly that I can't see the SIM card?

Well you see, that's how I felt you would start with it, but just then my wife called me to the baby and I didn't edit the post to mention it anymore. While testing I have the card, I had to temporarily transfer it to the phone as I was taking the photo. Hence the lack of card in the photo. Photo with card:
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The resistors in the photo are 10k + 10k and 10k

Maybe it's a photo issue but it's kind of like that with GSM Tx -> white cable -> 1K resistor -> and end

You have a good eye, but before you wrote I noticed it too and corrected it. This is a new picture, which shouldn't be questionable. I'm not strong with electrical stuff, hence my various mistakes, so far I've been coding games in CPP/C# and more recently I've been playing around a bit with Arduino.

I've been wondering what's wrong with it, I'm wondering if it's because of the voltage difference, as the Arduino Nano Sense is 3.3V max, and the GSM module is powered by 5V, and the GDNs need to be connected. I don't know what the voltage difference on the serial ports is then. The current symptoms are that when I connect the GDN's, sending any command I don't even get a print of the command in the serial monitor, and when I disconnect the GDN's I get partial bushes, truncated command prints followed by bushes, the cause of the resistors from what I noticed.

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