<![CDATA[4-20 mA Unit with wemos S2 mini ESP32]]>Hello,
I want to use the 4-20 mA unit with a wemos S2 mini with ESP32 chip but I am not able to get some data from it.
I had a look at the github examples and made a program to show the current on a display. Display is working and I can find the unit with an i2c scanner.
Arduino gives no mistakes during compiling but it doesn`t work. Any ideas ?
Thank you

Here is my code:

#include <Wire.h>
#include <Arduino.h>
#include <U8g2lib.h>

#include "MODULE_4_20MA.h"

U8G2_SSD1309_128X64_NONAME2_F_HW_I2C u8g2(U8G2_R0,U8X8_PIN_NONE);

const byte led_gpio = 15;   // LED GPIO 15

MODULE_4_20MA cr;

void setup() {
  Wire.begin(33, 18);  // SDA pin 33, SCL pin 18
  u8g2.begin();
  pinMode(led_gpio, OUTPUT);
}
 
void loop() {
  float current = cr.getCurrentValue(0);

  u8g2.firstPage();
  do {

    u8g2.setFont(u8g2_font_ncenB10_tr);
    u8g2.drawStr(0,20,"Strom:");
    u8g2.setCursor(0, 40);
    u8g2.print(current);
  } while ( u8g2.nextPage() );
  
  digitalWrite(led_gpio, HIGH);
    delay(1000);
  digitalWrite(led_gpio, LOW);
  delay(1000);   
}
]]>https://community.m5stack.com/topic/7450/4-20-ma-unit-with-wemos-s2-mini-esp32RSS for NodeSun, 08 Mar 2026 23:47:08 GMTFri, 28 Mar 2025 13:54:27 GMT60<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Mon, 07 Apr 2025 06:44:43 GMT]]>@obstbauer TBH if you are using M5Stack modules/units with not M5Stack controllers maybe its worth to have at least one M5Controller (atom?stick? )to be able to check module functionality

]]>https://community.m5stack.com/post/28825https://community.m5stack.com/post/28825Mon, 07 Apr 2025 06:44:43 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Sun, 06 Apr 2025 21:44:30 GMT]]>thank you, but I am still not able to read out or to set the cal current
M5Stack support doesn`t answer my mails... and it seems that there is nobody from the company around here, I think I will change to another board with better support

]]>https://community.m5stack.com/post/28820https://community.m5stack.com/post/28820Sun, 06 Apr 2025 21:44:30 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Fri, 04 Apr 2025 14:05:33 GMT]]>@obstbauer this is uiflow example with raw value and float too

ain21.PNG ain20.jpgain22.PNG

]]>https://community.m5stack.com/post/28798https://community.m5stack.com/post/28798Fri, 04 Apr 2025 14:05:33 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Fri, 04 Apr 2025 12:38:29 GMT]]>change to a raspberry PI4 seems to be no solution too.....
it woud be nice if there would be a better documentation for people who want to use the units outside the m5stack universum....

]]>https://community.m5stack.com/post/28797https://community.m5stack.com/post/28797Fri, 04 Apr 2025 12:38:29 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Fri, 04 Apr 2025 12:27:43 GMT]]>I see really strange behaviour and I don't know the reason and I get no answers from the support.....
The example code from M5Stack say that the currentvalue should be divided by 100:

canvas.printf("Current:%.2fmA", (float)(meter.getCurrentValue(0)) / 100.0);

The values I get I have to divide by 10 to get the right current in mA.... and the other issue is that I can only use half of the measurement range, at 12.5 mA the ADC sends 65520...

maybe someone has an idea ?

]]>https://community.m5stack.com/post/28796https://community.m5stack.com/post/28796Fri, 04 Apr 2025 12:27:43 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Thu, 03 Apr 2025 07:54:55 GMT]]>@robski yes maybe in uiflow2 but the function for the c program asks for an index and a value

]]>https://community.m5stack.com/post/28768https://community.m5stack.com/post/28768Thu, 03 Apr 2025 07:54:55 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Thu, 03 Apr 2025 07:49:06 GMT]]>@obstbauer haven't used index value

in uiflow2 ..ain4_20ma_0.set_cal_current(10) to set 10mA
ain4_20ma_0.set_cal_current(20) to set 20mA

]]>https://community.m5stack.com/post/28767https://community.m5stack.com/post/28767Thu, 03 Apr 2025 07:49:06 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Thu, 03 Apr 2025 07:31:47 GMT]]>@robski what value do you take for "index" in the function

void MODULE_4_20MA::setCalCurrent(uint8_t index, uint16_t value)
]]>https://community.m5stack.com/post/28766https://community.m5stack.com/post/28766Thu, 03 Apr 2025 07:31:47 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Tue, 01 Apr 2025 12:58:29 GMT]]>@obstbauer yeah thats the registers table, I used Uiflow2 with calibration block but you are using not M5Stack controller I see

]]>https://community.m5stack.com/post/28743https://community.m5stack.com/post/28743Tue, 01 Apr 2025 12:58:29 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Tue, 01 Apr 2025 12:56:11 GMT]]>@robski ok I think I found it:

thank you I will try tomorrow

0d731077-cf0a-4752-ae2d-318aa42b8f92-grafik.png

]]>https://community.m5stack.com/post/28742https://community.m5stack.com/post/28742Tue, 01 Apr 2025 12:56:11 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Tue, 01 Apr 2025 12:20:58 GMT]]>@obstbauer thats what i did with mine initially, calibrate with known current value

]]>https://community.m5stack.com/post/28741https://community.m5stack.com/post/28741Tue, 01 Apr 2025 12:20:58 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Tue, 01 Apr 2025 12:11:00 GMT]]>@robski thanks for the answer

so you mean if I measure with multimter 4.0 mA (which is true for the sensor) and the unit shows me 7.2 mA I should set the calibrated value to 4.0 ?

Because this is not mentioned anywhere in a readme file or manual or in the description of the device, and it is not made in the example file at github
but I am a beginner....

]]>https://community.m5stack.com/post/28740https://community.m5stack.com/post/28740Tue, 01 Apr 2025 12:11:00 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Tue, 01 Apr 2025 10:51:44 GMT]]>@obstbauer try calibration function based on what you see with multimeter

]]>https://community.m5stack.com/post/28739https://community.m5stack.com/post/28739Tue, 01 Apr 2025 10:51:44 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Tue, 01 Apr 2025 10:36:30 GMT]]>it seems that I still have a problem....
I have a current reading but the value is wrong,
I get soemthing around 7.2 mA instead of 4 mA.
I can measure the 4 mA with a multimeter in the circuit and the sensor should send 4 mA, so this is ok, but the M5Stack unit shows 7.2 mA and I don't understand why ? Any ideas ?
My sensor is passive, I connected 24 V to the 4-20mA unit and all three jumpers are installed
What is the meaning of the function "getCalCurrent" ? It is neessary for the current measurement ? It is necessary to set a "ref current" ?

Thank you!

]]>https://community.m5stack.com/post/28738https://community.m5stack.com/post/28738Tue, 01 Apr 2025 10:36:30 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Sat, 29 Mar 2025 20:51:46 GMT]]>@felmue Hello,
thank you very much, it works !
I added

cr.begin(&Wire, MODULE_4_20MA_ADDR, 33, 18, 100000UL);

to void setup

]]>https://community.m5stack.com/post/28714https://community.m5stack.com/post/28714Sat, 29 Mar 2025 20:51:46 GMT<![CDATA[Reply to 4-20 mA Unit with wemos S2 mini ESP32 on Fri, 28 Mar 2025 15:00:21 GMT]]>Hello @obstbauer

I think you might want to call cr.begin() in setup to set stuff like the proper I2C address for the library to use. See here.

Thanks
Felix

]]>https://community.m5stack.com/post/28704https://community.m5stack.com/post/28704Fri, 28 Mar 2025 15:00:21 GMT