MHZ19 CO2 problem

[MariusLaurinaitis]

Hello Xose,, I have same problem witth MHZ19 , maybe here's the same problem with the serial? Does it work for you? Thanks

[MariusLaurinaitis]

UPDATE: Espurna: MHZ19 @ SwSerial(13,15) MHZ19_RX_PIN -> 13 MHZ19_TX_PIN -> 15

I did not compil the new one, just: I swapped the wires only (I'll switch to RX and TX) and worked. But maybe you need to specify a PIN so that it does not mix others?

MHZ19 rx -> Wemos pin 15 MH19 TX -> Wemos pin 13

[xoseperez]

Sorry, do you mean GPIO 13 must be connected to the MHZ19 TX?

[MariusLaurinaitis]

Yes: GPIO 13 must be connected to the MHZ19 TX Thats work for me

[xoseperez]

Well, that's right, in the definition 13 is RX (from the device point of view) and must be connected to sensor TX.

[IvanUA]

Hi! I have the same problem - Error reading data from MH-Z19. Power source for MH-Z19 - external 5V.

Is there any way to debug MHZ19?

[MariusLaurinaitis]

did you swapped RX and TX?

[IvanUA]

Of course, many times. Gpio 13,15 (rx,tx and vice versa) Gpio 1,3 No success

Old one MH-Z19 (1st generation)

[xoseperez]

I'm not much into these sensors and I don't know what changes were there between different generations... @IvanUA, do you have a working code for your sensor?

[IvanUA]

Hi. Now I'm not sure about working condition of my MHZ19 (couldn't get it work directly through USB-UART). I'll will take a try with another one. Thank you.

[jsponz]

@MariusLaurinaitis, I have some problems when compiling for having support for MHZ19 -> https://github.com/xoseperez/espurna/issues/1063

Any idea?

Thanks!

[MariusLaurinaitis]

did you swapped RX and TX?

P.S. UPDATE: Espurna: MHZ19 @ SwSerial(13,15) MHZ19_RX_PIN -> 13 MHZ19_TX_PIN -> 15

I did not compil the new one, just: I swapped the wires only (I'll switch to RX and TX) and worked. But maybe you need to specify a PIN so that it does not mix others?

MHZ19 rx -> Wemos pin 15 MH19 TX -> Wemos pin 13

[jsponz]

I tried it as well, but the same library error. I have a new installation, following all the steps of the guideline...

Which libraries are you using?

Thanks!

[MariusLaurinaitis]

I tried 1.13.1 with all libraries

[jsponz]

same here :-(

[jsponz]

@MariusLaurinaitis It worked finally. Wrong reference on the libraries.

@IvanUA Does it work for you? I have the same:

[236659] [SENSOR] Error reading data from MHZ19 @ SwSerial(14,15) (error: 5) [242669] [SENSOR] Error reading data from MHZ19 @ SwSerial(14,15) (error: 5)

I have changed the pins, but with the same result.

Any idea? How do you know it is a first generation product?

[MariusLaurinaitis]

I will try in the evening

[derlucas]

try skipping the checksum check in MHZ19Sensor.h around line 181.

if ((buffer[0] == 0xFF) && (buffer[1] == 0x86)) {

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[stale[bot]]

This issue will be auto-closed because there hasn't been any activity for two months. Feel free to open a new one if you still experience this problem.

[berezovskyi-oleksandr]

I believe that I faced same problem with checksum calculation.

In calculation loop, there is next line: for (unsigned char i = 1; i < MHZ19_REQUEST_LEN-1; i++) { This definition will let sum from 1 till 7 (MHZ19_REQUEST_LEN - 1).

According to datasheet (page 9) there should be sum from 1 till 8.

After replacing MHZ19_REQUEST_LEN with MHZ19_RESPONSE_LEN , calculations became valid.

[ruimarinho]

@berezovskyi-oleksandr I have applied your suggested change but I still have the same issue. Tried multiple pins as well.