Odd numbers are read correctly, even numbers not

[sjfaustino]

When using the code below with a SDM120C:
`#include <SDM.h> //import SDM template library

SDM<2400, D1, D2> sdm; //SDM120C baud, rx pin, tx pin

void setup() {
Serial.begin(115200); //initialize serial
sdm.begin(); //initalize SDM220 communication baudrate
}

void loop() {

Serial.print("Frequency: ");
Serial.print(sdm.readVal(SDM120C_FREQUENCY), 2); //display frequency
Serial.println("Hz");

Serial.print("Voltage: ");
Serial.print(sdm.readVal(SDM120C_VOLTAGE), 2); //display voltage
Serial.println("V");

delay(1000); //wait a while before next loop
}`
I get:

Frequency: 50.00Hz
Voltage: 228.70V
Frequency: 50.00Hz
Voltage: nanV
Frequency: 50.00Hz
Voltage: nanV
Frequency: 50.00Hz
Voltage: nanV
Frequency: 50.00Hz
Voltage: nanV
Frequency: 50.04Hz
Voltage: nanV
Frequency: 50.00Hz
Voltage: nanV

If I swap the read order as on the code below:
`#include <SDM.h> //import SDM template library

SDM<2400, D1, D2> sdm; //SDM120C baud, rx pin, tx pin

void setup() {
Serial.begin(115200); //initialize serial
sdm.begin(); //initalize SDM220 communication baudrate
}

void loop() {

Serial.print("Voltage: ");
Serial.print(sdm.readVal(SDM120C_VOLTAGE), 2); //display voltage
Serial.println("V");

Serial.print("Frequency: ");
Serial.print(sdm.readVal(SDM120C_FREQUENCY), 2); //display frequency
Serial.println("Hz");

delay(1000); //wait a while before next loop
}`
I get:

Voltage: 231.20V
Frequency: 50.00Hz
Voltage: 230.80V
Frequency: nanHz
Voltage: 230.80V
Frequency: nanHz
Voltage: 230.80V
Frequency: nanHz
Voltage: 230.80V
Frequency: nanHz
Voltage: 231.30V
Frequency: nanHz

[beireken]

Please try a delay(50); between each sdm.readVal.
It never works without here.

[sjfaustino]

A delay(1) between reading each value seems to be sufficient.
Since 1ms is such a small delay, would it not be wise to add it on the library so that the user doesn't have to worry?

      delay(1);
      if (_dere_pin != NOT_A_PIN)                                               //transmit to SDM  -> DE Enable, /RE Disable (for control MAX485)

[reaper7]

I can add this,
but I never had such a problems
I read all values one-by-one without any delay:

    sdmval.voltage = sdm.readVal(SDM220T_VOLTAGE);
    sdmval.current = sdm.readVal(SDM220T_CURRENT);
    sdmval.power = sdm.readVal(SDM220T_POWER);
    sdmval.frequency = sdm.readVal(SDM220T_FREQUENCY);
    sdmval.energy = sdm.readVal(SDM220T_TOTAL_ACTIVE_ENERGY);

my config: SDM220 at 4800 baud

maybe baudrate affected this?

If I find some free time, then I insert some debug code with count wrong/nan reading

[beireken]

Not sure it's Baud related. I have 120c and 630 with 2400 and 9600 baud rate.
They both show this behaviour.

[reaper7]

After 1 hour of tests with error counter, I don't have any wrong readings.

this is my code (sorry but not usable as is because it uses my priv helper lib for wifi connection/ota/oled)
as You see, I reading all values one-by-one without any delay between.
I add errors counter variable (errorscnt), incremented every 1000ms loop, if any of reading values are NAN,
but all readings from last hour (every 1000ms) are good!

#include <ESP8266WiFi.h>

#include <ESPAsyncTCP.h>
#include <ESPAsyncWebServer.h>
#include <AsyncJson.h>

#include <ThingSpeak.h>

#include "ESP8266r7Helper.h"
#include "SDM.h"

AsyncWebServer server(80);

WiFiClient  client;

unsigned long myChannelNumber = xxxxxx;
const char * myWriteAPIKey = "XxXxXxXxXxXxXxXxXx";

unsigned long lastsdmreadtime = 0;                //store time of last smd read

bool dtardy = false;

uint16_t errorscnt = 0;                           //error counter for debug

//------------------------------------------------------------------------------
SDM<> sdm;

struct sdm_values {
  float voltage;
  float current;
  float power;
  float frequency;
  float energy;
} sdmval;
//------------------------------------------------------------------------------
void jsonrequest(AsyncWebServerRequest *request) {
  if (dtardy) {
    AsyncJsonResponse * response = new AsyncJsonResponse();
    JsonObject& root = response->getRoot();
    root["rp"] = String(sdmval.power,1);
    root["kw"] = String(sdmval.energy,2);
    root["rv"] = String(sdmval.voltage,1);
    root["rc"] = String(sdmval.current,2);
    root["rf"] = String(sdmval.frequency,2);
    root["er"] = String(errorscnt);

    response->setLength();
    request->send(response);
    request->client()->close();
  } else {
    request->send(404);  
  }
}
//------------------------------------------------------------------------------
void outrequest(AsyncWebServerRequest *request) {
  int params = request->params();
  for(int i=0;i<params;i++){
    AsyncWebParameter* p = request->getParam(i);
    Serial.printf("GET[%s]: %s\n", p->name().c_str(), p->value().c_str());
  }
  request->send(200, "text/plain", "OK");
}
//------------------------------------------------------------------------------
void setup() {
  devicename = "PWRMETER";

  sdmval.voltage = NAN;
  sdmval.current = NAN;
  sdmval.power = NAN;
  sdmval.frequency = NAN;
  sdmval.energy = NAN;
  
  Serial.begin(115200);

  oledinit();
  wifiinit();
  otainit();  
  
  sdm.begin();

  server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
    request->send(200, "text/plain", String(ESP.getFreeHeap()));
  });  
  server.on("/data.json", HTTP_GET, jsonrequest);
  server.on("/out", HTTP_GET, outrequest);
  server.onNotFound([](AsyncWebServerRequest *request){
    Serial.println("404: not found");
    request->send(404);
  });
  server.begin();  

  Serial.println(ESP.getFreeHeap());
  oledprintline((String)ESP.getFreeHeap());

  delay(2000);
}
//------------------------------------------------------------------------------
void loop() {
  static unsigned long tsupload = 0;
  static float lastenergy = -1.00;
  static float sumpower = 0.00;
  static float measurecnt = 0.00;
  static uint16_t minutes = 0;

  float tmpvoltage = NAN;
  float tmpcurrent = NAN;
  float tmppower = NAN;
  float tmpfrequency = NAN;
  float tmpenergy = NAN;
  
  if ((!otalock) && (millis() >= (lastsdmreadtime + SDM_READ_EVERY))) {
    lastsdmreadtime = millis();

    tmpvoltage = sdm.readVal(SDM220T_VOLTAGE);
    tmpcurrent = sdm.readVal(SDM220T_CURRENT);
    tmppower = sdm.readVal(SDM220T_POWER);
    tmpfrequency = sdm.readVal(SDM220T_FREQUENCY);
    tmpenergy = sdm.readVal(SDM220T_TOTAL_ACTIVE_ENERGY);

    if ((isnan(tmpvoltage)) || (isnan(tmpcurrent)) || (isnan(tmppower)) || (isnan(tmpfrequency)) || (isnan(tmpenergy))) {   // if one of reading values is a NAN then set "dataready flag to false

      dtardy = false;
      errorscnt++;                                                                                                          // increment errorscnt for debug

      sdmval.voltage = 0.00;
      sdmval.current = 0.00;
      sdmval.power = 0.00;
      sdmval.frequency = 0.00;
      sdmval.energy = 0.00;

    } else {                                                                                                                // else -> every values != NAN

      sdmval.voltage = tmpvoltage;
      sdmval.current = tmpcurrent;
      sdmval.power = tmppower;
      sdmval.frequency = tmpfrequency;
      sdmval.energy = tmpenergy;

      dtardy = true;

      if (lastenergy == -1.00) {
        lastenergy = sdmval.energy;
      }

      sumpower += sdmval.power;
      measurecnt = measurecnt + 1.00;
  
      char buff[48] = {};
      sprintf(buff, "V:%7.2f\nA:%7.2f\nP:%7.2f\nF:%7.2f\0", sdmval.voltage, sdmval.current, sdmval.power, sdmval.frequency);
      
      oledprintline(buff, 0, true, Cousine_Bold_10, TEXT_ALIGN_CENTER);
  
      if (lastsdmreadtime >= (tsupload + 60000)) {
        char floatchr[12];

        minutes++;
  
        tsupload = lastsdmreadtime;
        
        ThingSpeak.begin(client);
        ThingSpeak.setField(1,dtostrf(sdmval.voltage,0,2,floatchr));
        ThingSpeak.setField(2,dtostrf(sdmval.current,0,2,floatchr));
        ThingSpeak.setField(3,dtostrf(float(sumpower / measurecnt),0,2,floatchr));
        ThingSpeak.setField(4,dtostrf(sdmval.frequency,0,2,floatchr));
        if (minutes == 59) {
          ThingSpeak.setField(5,dtostrf((sdmval.energy - lastenergy),0,2,floatchr));
          minutes = 0;
          lastenergy = sdmval.energy;
          ThingSpeak.setField(6,errorscnt);                                                                                         // every hour send errorscnt value to thingspeak for debug
          errorscnt = 0;                                                                                                            // errorscnt uploaded, set to 0
        }    
        ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey);
  
        measurecnt = 0.00;
        sumpower = 0.00;
      }
    }
  }
  ArduinoOTA.handle() ;                           // Check for OTA
}

this is a prototype code but works ~129days without a problems

[reaper7]

one more thing...
how is Your connection between SDM and converter?
two wire (A&B) or three wire (A&B&GND)
I have 3 wire...

[sjfaustino]

I'm using a Wemos D1 mini (esp8266) connected to this ttl2rs485: https://www.aliexpress.com/item/TTL-turn-RS485-module-485-to-serial-UART-level-mutual-conversion-hardware-automatic-flow-control/32709226383.html

Wemos mini to TTL2RS485:
Wemos D1 to TX TTL2RS485
Wemos D2 to RX TTL2RS485
Wemos GND to GND TTL2S485
Wemos 3.3V to VCC TTL2RS485

TTL2RS485 to SDM120C
B to pin9
A to pin10
GND not connected (don't know what is the gnd pin on the sdm120c, maybe 8?)

So, 2 wire. Also, no 120 ohm resistor in use ( I believe it is only necessary on long cable runs).

I sugest adding a ifdefine add_sdm_delay to the library and let the user do a #define add_sdm_delay if he wants.

[reaper7]

I can't reproduce this error.
On my hardware configuration, example from this lib and my other project works without problem,
so...at this moment please add delays to Your main program or clone this lib and do this on Your copy.

GND...maybe 8:
http://techfreak.pl/miernik-zuzycia-energii-elektrycznej-sdm120/sdm120-connection/
http://eastron.inf.ua/SDM120.html

[reaper7]

after 14 hours still no errors

[reaper7]

@beireken - do You check if this problem also exists when converter is connected via hardware serial?

I checked this problem whole weekend, code read all fourteen SDM220 registers at once in loop every 2sec and after 2 days I have only 37 errors
where number of all reading = 48h * 60m * (60s/2) = 86400 readings

I must check if problem is a timeout/bad checksum/not enough bytes read

[beireken]

@reaper7 Do you mean changing the library to function with hardware serial and not softserial?
Or just using the pins of tx and rx and not random other.?

[reaper7]

no no, this lib is ready for use with hardware serial,
user must set at top of sketch:

#define USE_HARDWARESERIAL

before:

#include <SDM.h> 

If You not tested yet hardware serial functionality of this lib then no question :D

Today I added a few fix, maybe some reading errors disappear...

[beireken]

Hmm I did not know that. I will test this when I get the chance and report back.

[reaper7]

ok, tnx.
You can test software serial too, without any delay between each sdm read