Arduino Code for HRV temperatures to OpenHAB

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Arduino Code for HRV temperatures to OpenHAB

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563 posts

Ultimate Geek
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#1562650 30-May-2016 20:46

Another couple photo's for the hell of it. Have added a switch to the board now to flick on if I need to flash the ESP

Debugging or flashing uses remaining plugs:

The 3x7cm PCB board fits really nicely in the wall:

TommySharp

135 posts

Master Geek
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#2884916 11-Mar-2022 13:03

I'd be keen to hear how this integration is going 6 years on.....

I've moved into a new home and it has an HRV with the newer touch screen control panel, will be interesting to hear thoughts on if this can still be integrated?

chimera

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#2884918 11-Mar-2022 13:07

TommySharp:

I'd be keen to hear how this integration is going 6 years on.....

I've moved into a new home and it has an HRV with the newer touch screen control panel, will be interesting to hear thoughts on if this can still be integrated?

Hey Tommy,

Still going strong, although am still running the original control panel. I don't know if the newer touch screen panel also means a newer controller and therefore different serial messages. If it's just a control panel upgrade, but same data sent, then it should just work.

I'd suggest giving it a try. I wrote an instructable for it which may help...

https://www.instructables.com/HRV-Wireless/

Cheers

EdmundSS

1 post

Wannabe Geek

#2904582 20-Apr-2022 21:52

TommySharp:

I've moved into a new home and it has an HRV with the newer touch screen control panel, will be interesting to hear thoughts on if this can still be integrated?

I've also just moved into a house with a c.15 year old steel box HRV ... that doesn't work :-( A service guy came, concluded the control panel was broken, and offered to install a modern one (for $500!). It plugs into the same RJ12 cable, so at least some modern HRV kit still uses the same signalling.

millst

26 posts

Geek
+1 received by user: 7

#2976869 3-Oct-2022 16:19

I'm just building this project so thanks to those who have put so much work into it.
Has anyone used it to completely replace and throw away the HRV controller.
The HRV one does some pretty dumb stuff sometimes, especially when you are trying to heat a room even though it thinks its too warm in the house.
I'd love to feed in humidity data to make it a much smarter system.

Has anyone else had success in this area?

chimera

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Ultimate Geek
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#2976878 3-Oct-2022 16:52

you're welcome. glad someone could make use of it.

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millst

26 posts

Geek
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#2976884 3-Oct-2022 17:48

Is there an updated version of the code?
The version posted at www.chimera.co.nz/electronics/hrv-esp8266.ino
returns the following errors...

hrv_listen:159:5: error: 'iHRVLastFan' was not declared in this scope; did you mean 'iHRVLastFanSpeed'?

hrv_listen:317:52: error: 'iFanSpeed' was not declared in this scope; did you mean 'iHRVFanSpeed'?

hrv_listen:442:47: error: 'iHRVLastFan' was not declared in this scope; did you mean 'iHRVLastFanSpeed'?

hrv_listen:455:9: error: 'iFanSpeed' was not declared in this scope; did you mean 'iHRVFanSpeed'?

'iHRVLastFan' was not declared in this scope; did you mean 'iHRVLastFanSpeed'?

millst

26 posts

Geek
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#2982444 13-Oct-2022 20:23

Just as an update on this, I've made quite a bit of progress in working with the HRV system.
I discovered that if using the Wemos D1, it runs off 5V and handled 5V ttl, so you can wire it up directly to the HRV system with no external boards or level shifters.
I've also had success in controlling the HRV, in particular, my goal was to replace the control panel with my own board which would be controlled by my home automation system so that it did not clash with other heating.

The trick turned out to be to use the half duplex mode in the ESP software serial library which can flick the same pin between rx and tx.

So I can now send a command to the fan controller, set the speed of the fan and then wait for the reply with the temperature, all on the same wire and pin.

I'm tidying up the code a bit and will post photos and code here with instructions on how to do a much simpler implementation than what is described here.

ivanp

6 posts

Wannabe Geek
+1 received by user: 1

#2982466 14-Oct-2022 00:17

millst:

So I can now send a command to the fan controller, set the speed of the fan and then wait for the reply with the temperature, all on the same wire and pin.

I'm tidying up the code a bit and will post photos and code here with instructions on how to do a much simpler implementation than what is described here.

Wow that would be great!

I am so tired of the standard logic in my ultra-old HRV, would love to replace it with something custom that would make more sense to me. Such as run ventilation at higher fan speed at late night time and especially early morning, when moisture level in bedrooms is the highest...

millst

26 posts

Geek
+1 received by user: 7

#2982474 14-Oct-2022 07:29

Yes, the HRV algorithms are practically useless.

My pet peeve is that it can be running flat out to cool down your house while you have the heating cranked.

I'll be implementing this as basically a remote fan control and a way to get the roof temperature out, and then you can shift all the logic to your home automation system which should be aware of humidity and temperatures.

TommySharp

135 posts

Master Geek
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#2982488 14-Oct-2022 08:48

Since we got a ducted heat pump I just have the HRV on a basic plug timer to turn it of/on so it runs for 2 hours a day just to get some fresh air in...
I'd also be keep to see your approach especially to getting "control" of the HRV.

Which version do you have? Mine is one with a little touch screen controller.

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millst

26 posts

Geek
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#2982537 14-Oct-2022 11:26

ok, here is some code, before I radically customise it to my needs.

This code receives a UDP message on port 1111 containing the fan speed you want to set 0x00 is off and 0x64 is full speed.

To use it,

- just connect the Black wire from your HRV fan controller in the roof to ground on the Wemos D1
- connect the white wire to VIN
- connect the green wire to pin D5

Thats it, no resistors, or power converters or TTL converters needed, the Wemos D1 works on 5V.

The last step is to throw away your HRV control panel, don't try to run it at the same time, it just wont work, you can only have one master on the bus and your arduino is now going to be the boss.

I have a TFT screen on order so when that arrives I'm going to modify this code to display HRV like things on the screen and mount it all back under the HRV panel, may even connect up some buttons.

#include <SoftwareSerial.h>
#include <ESP8266WiFi.h>
#include <WiFiUdp.h>

#define D5 (14)
#define D6 (12)

#define MSGSTARTSTOP 0x7E

SoftwareSerial hrvSerial;

#define localPort 1111

// Wifi
const char* ssid = "SSID";
const char* password = "password";

IPAddress ip2(192, 168, 0, 99); // this is where we will send some UDP messages, you may not need this
WiFiUDP Udp;

// The MAC address of the Arduino
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

// Wifi Client
WiFiClient wifiClient;
IPAddress ipadd;

char packetBuffer[255];

// Temperature from Roof or House?
char eTempLoc;

// TTL hrvSerial data array, bIndex, bIndex of checksum and temperature
int iLoop;
byte inData[10];
byte bIndex;
byte bChecksum;
bool bStarted = false;
bool bEnded = false;

int iTotalDelay = 0;

// Temperature for sending to MQTT
float fHRVTemp;
int iHRVControlTemp;
int iHRVFanSpeed;

byte targetFanSpeed = 0x00; //we will send the fan the speed we want it to run at

void setup() {
// put your setup code here, to run once:
//hrvSerial.begin(1200);
hrvSerial.begin(1200, SWSERIAL_8N1, D6, D6, false, 256);
hrvSerial.enableIntTx(false);
// Debug USB Serial
Serial.begin(115200);

// Initialize defaults
bIndex = 0;
bChecksum = 0;
iTotalDelay=0;

Udp.begin(localPort);
}

void loop() {
// put your main code here, to run repeatedly:


startWIFI();
//int packetSize = Udp.parsePacket();
if (Udp.parsePacket()) {
Serial.println("packet received");
int len = Udp.read(packetBuffer, 255);
if (len > 0) {
packetBuffer[len] = 0;
Serial.println(packetBuffer);
}
targetFanSpeed = packetBuffer[0];
}

checkSwSerial(&hrvSerial); //send fan speed to fan controller and receive back roof temperature

delay(1500);

}

void checkSwSerial(SoftwareSerial* ss) {
byte ch;
byte message[] = {0x31,0x01,0x9E,targetFanSpeed,0x0E,0x80,0x70};

// Subtract from zero
int iChar = 0;
int iLess;
byte bCalc;
String sCalc;

// Subtract each byte in ID and data
for (int iPos=0; iPos < sizeof(message); iPos++)
{
iLess = message[iPos];
iChar = iChar - iLess;
}

// Convert calculations
bCalc = (byte) (iChar % 0x100);
sCalc = decToHex(bCalc, 2);

ss->enableTx(true); //this is the magic, tell the arduino to switch the pin into TX mode so we can send and receive on the same wire.
//while (Serial.available())
{
Serial.println("send: ");
int i;
ss->write(MSGSTARTSTOP); //send start message first
for(i=0; i<sizeof(message); i++){
ss->write(message[i]);
Serial.print(message[i],HEX); //send the stuff its expecting including our new fan speed
}
ss->write(bCalc);//send checksum
ss->write(MSGSTARTSTOP); //send stop bit

}
ss->enableTx(false); //this is the magic, tell the board to start listening on the same pin we just wrote to
Serial.println("wait");

// wait 1 second for the reply from SOftwareSerial if any
delay(1000);
if (ss->available()) {
Serial.print(PSTR("\nResult:"));
while (ss->available()) {
ch = (byte)ss->read();
Serial.print(ch < 0x10 ? PSTR(" 0") : PSTR(" "));
Serial.print(ch, HEX);
int inChar = int(ch);

if (inChar == MSGSTARTSTOP || bIndex > 8)
{
// Start if first time we've got the message
if (bIndex == 0)
{
Serial.println("Started Block");
bStarted = true;
}
else
{
bChecksum = bIndex-1;
bEnded = true;
break;
}
}

if (bStarted == true)
{
// Double check we actually got something
if (sizeof(inChar) > 0)
{
Serial.print(inChar, HEX);
inData[bIndex] = inChar;
bIndex++;
}
}
myDelay(1);
}
Serial.println();
}

String sHexPartOne;
String sHexPartTwo;
int iPos;

// Pull data out of the array, position 0 is 0x7E (start and end of message)
for (int iPos=1; iPos <= bIndex; iPos++)
{

// Position 1 defines house or roof temperature
if (iPos==1) { eTempLoc = (char) inData[iPos]; }

// Position 2 and 3 are actual temperature, convert to hex
if (iPos == 2) { sHexPartOne = decToHex(inData[iPos], 2); }
if (iPos == 3) { sHexPartTwo = decToHex(inData[iPos], 2); }

}
// Concatenate first and second hex, convert back to decimal, 1/16th of dec + rounding
// Note: rounding is weird - it varies between roof and house, MQTT sub rounds to nearest 0.5
fHRVTemp = hexToDec(sHexPartOne + sHexPartTwo);
fHRVTemp = (fHRVTemp * 0.0625);
int iHRVTemp;
iHRVTemp = (int) ((fHRVTemp * 2) + 0.5);
fHRVTemp = (float) iHRVTemp / 2;
String pubString;
pubString = String(fHRVTemp);

Serial.print(pubString);
Udp.beginPacket(ip2, localPort);
Udp.print("CeilingTemp:");
Udp.print(pubString);
Udp.endPacket();
}

//
// Convert from decimal to hex
//
String decToHex(byte decValue, byte desiredStringLength)
{

String hexString = String(decValue, HEX);
while (hexString.length() < desiredStringLength) hexString = "0" + hexString;

return hexString;
}

//
// Convert from hex to decimal
//
unsigned int hexToDec(String hexString)
{

unsigned int decValue = 0;
int nextInt;

for (int i = 0; i < hexString.length(); i++) {

nextInt = int(hexString.charAt(i));
if (nextInt >= 48 && nextInt <= 57) nextInt = map(nextInt, 48, 57, 0, 9);
if (nextInt >= 65 && nextInt <= 70) nextInt = map(nextInt, 65, 70, 10, 15);
if (nextInt >= 97 && nextInt <= 102) nextInt = map(nextInt, 97, 102, 10, 15);
nextInt = constrain(nextInt, 0, 15);

decValue = (decValue * 16) + nextInt;
}

return decValue;
}

//
// This function yields back to the watchdog to avoid random ESP8266 resets
//
void myDelay(int ms)
{

int i;
for(i=1; i!=ms; i++)
{
delay(1);
if(i%100 == 0)
{
ESP.wdtFeed();
yield();
}
}

iTotalDelay+=ms;

}

//
// Starts WIFI connection
//
void startWIFI()
{

// If we are not connected
if (WiFi.status() != WL_CONNECTED)
{
int iTries;
iTries=0;

Serial.println("Starting WIFI connection");
WiFi.mode(WIFI_STA);
WiFi.disconnect();
WiFi.begin(ssid, password);

// If not WiFi connected, retry every 2 seconds for 15 minutes
while (WiFi.status() != WL_CONNECTED)
{
iTries++;
Serial.print(".");
delay(2000);

// If can't get to Wifi for 15 minutes, reboot ESP
if (iTries > 450)
{
Serial.println("TOO MANY WIFI ATTEMPTS, REBOOTING!");
ESP.reset();
}
}

Serial.println("");
Serial.println("WiFi connected");
Serial.println(WiFi.localIP());

// Let network have a chance to start up
myDelay(1500);

}

}