Power consumption of Anarduino grows after FTDI adapter disconnected

Development Tools IDE 1.x
1

Hello,

I'm using Anarduino MiniWireless with LoRa module - Anarduino MiniWireless Details

Anarduino powered from LiPo battery 4.2V to GND and Vin pins directly, also in this chain there is multimeter for measuring power consumption.

Also Anarduino connected to FTDI-USB adapter, but without "Vcc" pin (only GND, CTS, TX, RX and DTR)
FTDI adapter connected to USB in my laptop and I can load program to Anarduino.

laptop -> USB -> FTDI(w/o Vcc) -> MCU[Anarduino] <- (A) -battery

Everything works ok.

I'm using this test code:

#include <RH_RF95.h>  
#include <SPI.h>  
#include <SPIFlash.h>  
#include <LowPower.h>  
  
RH_RF95 rf95;  

SPIFlash flash(5);  //Anarduino

//SPIFlash flash(8, 0xEF30); // flash(SPI_CS, MANUFACTURER_ID)

 
void setup()  
{  

   Serial.begin(9600);
   Serial.println("start");
  
   rf95.init();  
   
      
   if (flash.initialize()) {
            Serial.print("SPI Flash Init OK ");
    }
    else Serial.println("SPI Flash Init FAIL!");

   Serial.flush();
   flash.sleep();
   rf95.sleep();  
  
}  
  
void loop()  
{  
   LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); 

  
  }

Code makes device sleep and this is my main goal - get the lowest power consumption in sleep mode.

Also this code works ok and my multimeter shows about 40uA of power consumption. It's ok for my task.

But if I disconnect FTDI adapter from Anarduino:

MCU[Anarduino] <- (A) -battery

  • power consumption grows to 0.11mA. It is really not good for my device..

Note - all the digital and analog pins on Anarduino are disconnected and just floats so there no any reason to drain power.

I just don't understand - a lot of people say that they managed to get small power consumption around 6-7uA but seems it just means that they measure power with FTDI adapter connected to USB?
I think this is useless.
We need such power consumption on battery powered variant.
I can't believe it.. there are a lot а reports about devices that powered even from CR2032 and they work for years. How they work?

So I don't know what can I do next.
I just wonder if I'm only one who faced with this issue..
Because all who used these MCU have to disconnect Serial adapter from its device in usual mode. And as I see - it should lead to unexpectedly high energy consumption.
So why no one complains like me ?

2

UPD:

There is a jumper on FTDI adapter - it switches power from 5v to 3v.
I've switched it to 3V mode and Anarduino started consume 0.11mA in sleep mode with and without FTDI adapter connected.

So now at least I know that Anarduino LoRa minimum power consumption is 0.11mA or 110uA.

3

You had it set to use 5v logic levels. The idle state of a serial line is high, so the serial line was at 5v - so you were backpowering the device through the protection diode on the serial RX pin.