LoRa Resetting Arduino Pro Mini

Projects General Guidance
1

I am using an Arduino Pro mini 3.3V 8MHz connected to a LoRa Ra - 02. My pin connection is as follows,

D10 -------- NSS
D11 -------- MOSI
D12 -------- MISO
D13 -------- SCK
D2 ---------- DIO0
D4 ---------- RST

I am using the LoRa library by sandeep mistry. When I upload the example "LoRa Sender" code, the pro mini keeps resetting at transmission. It happens when transmitted at 433MHz.

#include <SPI.h>
#include <LoRa.h>

int counter = 0;

void setup() {
  Serial.begin(9600);
  while (!Serial);

  Serial.println("LoRa Sender");

  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }
}

void loop() {
  Serial.print("Sending packet: ");
  Serial.println(counter);

  // send packet
  LoRa.beginPacket();
  LoRa.print("hello ");
  LoRa.print(counter);
  LoRa.endPacket();

  counter++;

  delay(5000);
}

It wouldn't happen when I reduce the tx power to 12. Has this happened to anyone else?
is 12dBm the maximum power that I can transmit using a pro mini?
are there any workarounds to fix this?

2

Which type of Pro Mini ?

5V or 3.3V ?

3

3.3v 8MHz

4

Could be that the power supply your using is just not up to supplying the required current ?

There is a common issue with 3.3V Pro Minis in that the brownout reset voltage is often set at 2.7v, which is fine for 5V Pro Minis but not really for 3.3V ones. Reprogramming the fuses for a 1.8V brownout can help.

For 433Mhz ISM band use the legal power is often restricted to 10mW.

6

Thank you.
I also want you to know that I am planning on using ArduinoLowPower library to put the MCU to powerdown mode.
Do you think it can conflict with me manually reprogramming brownout fuses ?

7

I doubt it.

8

How far is the Antenna from the Pro mini ?
The RF could feed back into the circuit.

9

around 15cm away

10

How long is the coax cable?
Try to move the Ant away as far as possible (full length of the coax)

What power supply (max Amps) are you using?
Lora is Low power , around 100mA on full power when TX.

11

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I forgot to add this info.

12

I have used a Pro Mini 3.3 with a RA-02 without problems using pins

// RA-02 SS   to Pro Mini  D10
// RA-02 RST  to Pro Mini  D9
// RA-02 DIO0 to Pro Mini  D3  requires interrupt pin!!!!
// RA-02 MOSI to Pro Mini  D11
// RA-02 MIS0 to Pro Mini  D12
// RA-02 SCK  to Pro Mini  D13
// setpins() is therefore
// ***** note DIO0 requires a pin which enables interrupts, e.g. pro mini D3  *********
// setPins(int ss = LORA_DEFAULT_SS_PIN, int reset = LORA_DEFAULT_RESET_PIN, int dio0 = LORA_DEFAULT_DIO0_PIN);
//   LoRa.setPins(10, 9, 3);   // 10 for UNO and Pro Mini, 53 for Mega
13

I have been using LoRa modules extensivly with Pro Minis and bare bones Atmega328 boards for a long time.

Normally the antenna is real close, as in right on top of the Pro Mini, never had a reset problem when using a decent battery.

14

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This is the module and the antenna its a short cable around 10cm

The resetting of the board starts right after i flash the program. At that moment it is powered through the adapter.

I also have another pro mini where i have removed the voltage regulator and is powered using a MCP1700 and a LiPo battery.
when uploaded the same sketch, It sometimes runs a few loops without an issue and then gets stuck in a reset loop after a while. emphasized text

15

what was the power source you were using ?

16

Try LoraRF.h Library.

I also had freezing Nano's with Lora.h and LoRa RA 01.
The Lora.h library does not work with the Interrupt , disconnect the Interrupt pin and see if it stops working.

When I changed to LoraRF.h it never hanged up , running for a week transmitting every 10 seconds.

17

ran your program of post 1 on pro mini 3.3V (connections as post 1) ran OK

18

Is your power supply not experiencing a small voltage dip during transmission?
My power supply experiences a voltage dip of around 0.4V when transmitting at txpower(12)

19

I used a 7.2v 2000mAH Lion batt.

20

Really ?

How did you have the RA-01 connected ?

I cannot understand why the Library (LoRa.h) would be the cause of a Pro Mini 'freezing' at higher power levels.

By default the LoRa.h library does not use the DIO0 pin, so whether its connected or not should make no differance.

21

Yes .. The wiring is the same as 100's of examples all over the Internet.
The exact same wiring never hang up when I change to LoraRF.h.
When I reduced the TX Power all works ok.(Using LoRa.h)

Below is my old post regarding the freezing of Lora_Nano setup.

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Then repeatedly reading the registers mixed with some RF interference on the wires,tracks can cause corrupt data.

I agree that there might be other causes in the OP case.

The wiring that I used.
https://circuitdigest.com/microcontroller-projects/arduino-lora-sx1278-interfacing-tutorial