MH-Z19B Reading problem

Ouko · January 29, 2022, 3:53pm

Hi,

I tried multiple way to connect the MH-Z19B using Mycodo interface. First of all, using the mh-z19 3.1.1 project, I can easily retrieve data from the /dev/ttyS0 over a SSH connection to the pi with sudo python -m mh_z19 --all. That means, the sensor is working.

Now when I configure Mycodo mh-z19b input, there is nothing happening when trying to read the values. I had configured it to use /dev/ttyS0 and I also tried using a UART-USB converter instead of the TX-RX GPIO pins, not much success.

I don’t know what’s happening, but here is the log about the moment when mycodo tries to acquire data.

2022-01-29 10:40:31,407 - INFO - mycodo.controllers.controller_input_bd84bcbf - Activated in 403.7 ms
2022-01-29 10:40:31,407 - DEBUG - mycodo.daemon - Input controller with ID bd84bcbf-2890-45c0-bd69-9d9f0e392c39 activated.
2022-01-29 10:40:32,420 - DEBUG - mycodo.inputs.mh_z19b_bd84bcbf - No response
2022-01-29 10:40:32,456 - DEBUG - mycodo.controllers.controller_input_bd84bcbf - Adding measurements to InfluxDB with ID bd84bcbf-2890-45c0-bd69-9d9f0e392c39: {}
2022-01-29 10:40:37,407 - ERROR - mycodo.controllers.controller_input_670a2d3b - StopIteration raised 3 times. Possibly could not read input. Ensure it’s connected properly and detected.
2022-01-29 10:40:40,998 - ERROR - mycodo.controllers.controller_input_8a9cea18 - Mycodo is attempting to acquire measurement(s) from an Input that has already critically errored. Review the log lines following Input Activation to investigate why this happened.

Also, I did use a 5k resistor between my VCC and Tx, I really don’t know what to do from know since I can get reading through mh_z19.read() over ssh.

Thanks for you help.

KyleGabriel · February 5, 2022, 4:10pm

Are you sure you configured the Input correctly?

Em_Ka · May 13, 2022, 1:01pm

i have (hopefully) the same problem with the mh-z19b. or at least one aswell.

mycodo gives this error:

2022-05-13 14:44:23,172 - ERROR - mycodo.inputs.mh_z19b_a7e10268 - Error initializing, trying again in 5 seconds: Write timeout
Traceback (most recent call last):
  File "/var/mycodo-root/mycodo/abstract_base_controller.py", line 54, in try_initialize
    self.initialize()
  File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 153, in initialize
    self.abcoff()
  File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 201, in abcoff
    self.ser.write(bytearray([0xff, 0x01, 0x79, 0x00, 0x00, 0x00, 0x00, 0x00, 0x86]))
  File "/var/mycodo-root/env/lib/python3.9/site-packages/serial/serialposix.py", line 636, in write
    raise SerialTimeoutException('Write timeout')
serial.serialutil.SerialTimeoutException: Write timeout

i also tried using this one here directly, which worked out of the box

git clone https://github.com/UedaTakeyuki/mh-z19
./setup.sh
sudo python3 -m mh_z19

~/mh-z19 $ sudo python3 -m mh_z19
{"co2": 537}

thank you

KyleGabriel · May 13, 2022, 1:17pm

Providing just an error is not enough information to replicate your environment or diagnose the issue. You need to provide details about the physical connections as well as the software settings used to be able to investigate the issue.

Also, are you sure you have a MH-Z19B and not a MH-Z19? It looks like it’s failing on ABC, which is only present in the B version.

Em_Ka · May 13, 2022, 3:29pm

the label says MH-Z19B.
just tried the MH-Z19 (without B) input, but still the same

2022-05-13 17:23:21,402 - ERROR - mycodo.inputs.mh_z19_3a5b0e1b - Error initializing, trying again in 5 seconds: Write timeout
Traceback (most recent call last):
File “/var/mycodo-root/mycodo/abstract_base_controller.py”, line 54, in try_initialize
self.initialize()
File “/home/pi/Mycodo/mycodo/inputs/mh_z19.py”, line 141, in initialize
self.set_measure_range(self.measure_range)
File “/home/pi/Mycodo/mycodo/inputs/mh_z19.py”, line 194, in set_measure_range
self.ser.write(bytearray([0xff, 0x01, 0x99, 0x00, 0x00, 0x00, 0x13, 0x88, 0xcb]))
File “/var/mycodo-root/env/lib/python3.9/site-packages/serial/serialposix.py”, line 636, in write
raise SerialTimeoutException(‘Write timeout’)
serial.serialutil.SerialTimeoutException: Write timeout

i guess the problem is not the physical connection, as i get the correct values outside of mycodo ?

what software settings exactly?

thank you

KyleGabriel · May 13, 2022, 4:01pm

Physical connections of the hardware, any and all settings you configured in software… all of these are needed to diagnose an issue. None should be assumed.

Em_Ka · May 13, 2022, 5:10pm

i have it exactly like this
direct connection, no breadboard or anything

RXD(Sensor)->TXD(rpi)
TXD(Sensor)->RXD(rpi)
GND → GND
VIN → 5V

mh-z19b settings are all to default. /dev/ttyAMA0 - baudrate 9600

what settings are you mean? i have nothing configured yet. only turned everything to “on” in mycodo-rpi-settings

I2C Enabled: True
1-Wire Enabled: True
Serial Enabled: True
SPI Enabled: True
SSH Enabled: True
Pi Camera Enabled: False

KyleGabriel · May 13, 2022, 5:16pm

The Mycodo Input is configurable as well.

Em_Ka · May 13, 2022, 5:19pm

yes. all to default.

KyleGabriel · May 13, 2022, 6:09pm

Is /dev/ttyAMA0 the location of your serial device connected to the sensor?

KyleGabriel · May 13, 2022, 6:13pm

Have you searched similar issues on github? Here are some:

github.com/kizniche/Mycodo

MH-Z19B: CO2 Sensor Error

opened 08:31PM - 15 Mar 22 UTC

closed 02:52AM - 16 Mar 22 UTC

ChrisDavidRucker

### Describe the problem/bug *MH-Z19B CO2 sensor error. Specifically I was s…uccessful in reading the sensor from CLI using a python script to confirm the sensor is functional.* ![image](https://user-images.githubusercontent.com/81479977/158465749-0c1dcb41-7170-4519-975a-deb17fadc99c.png) ### Versions: - Mycodo Version: *8.12.9* - Raspberry Pi Version: *4B* - Raspbian OS Version: *Bullseye* ### Reproducibility Please list specific setup details that are involved and the steps to reproduce the behavior: 1. *Connect sensor.* 2. *Configure sensor.* 3. *Activate sensor.* 4. *Check live measurements page.* 5. *Check daemon log to confirm its not working.* ### Expected behavior *The sensor to show up in the "Live Measurements" page once correctly configured.* ### Screenshots ![image](https://user-images.githubusercontent.com/81479977/158466863-20d7438e-a77a-4fd1-8d65-8507d68e6e93.png) *![image](https://user-images.githubusercontent.com/81479977/158464987-2260d0e3-7ba3-4878-9e45-c87ab322c4c5.png)* ### Additional context (Daemon log) *ERROR - mycodo.controllers.controller_input_b1cf440c - initialize_variables() Exception: Write timeout Traceback (most recent call last): File "/var/mycodo-root/mycodo/controllers/base_controller.py", line 74, in run self.initialize_variables() File "/var/mycodo-root/mycodo/controllers/controller_input.py", line 317, in initialize_variables self.measure_input = input_loaded.InputModule(self.input_dev) File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 130, in __init__ self.initialize_input() File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 149, in initialize_input self.abcon() File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 205, in abcon self.ser.write(bytearray([0xff, 0x01, 0x79, 0xa0, 0x00, 0x00, 0x00, 0x00, 0xe6])) File "/var/mycodo-root/env/lib/python3.9/site-packages/serial/serialposix.py", line 636, in write raise SerialTimeoutException('Write timeout') serial.serialutil.SerialTimeoutException: Write timeout*

github.com/kizniche/Mycodo

MH-Z19b Issue.

opened 06:46PM - 21 Jun 21 UTC

closed 02:47AM - 30 Aug 21 UTC

ghost

I have seen similar issues, but in the past it says they have been patched throu…gh updates. And those posts are YEARS old. ### Describe the problem/bug Co2 sensor works perfectly with my Pi 2. Switch it to my Pi 4 with all the same updated OS and Mycodo. Wont run and gives me error messages. ### Versions: - Mycodo Version: [latest version] - Raspberry Pi Version: [4] - Raspbian OS Version: [Raspian, most recent version] ### Reproducibility Please list specific setup details that are involved and the steps to reproduce the behavior: 1. Start up Mycodo with the Co2 sensor attached 2. Rx to Tx, Tx to Rx. gnd to gnd, pwer to 5v 3. activate sensor with default uart path. 4. See error ### Expected behavior I use this sensor on my Pi 2 with no issues. The Pi 4 gives me this. Traceback (most recent call last): File "/var/mycodo-root/mycodo/controllers/base_controller.py", line 74, in run self.initialize_variables() File "/var/mycodo-root/mycodo/controllers/controller_input.py", line 317, in initialize_variables self.measure_input = input_loaded.InputModule(self.input_dev) File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 130, in __init__ self.initialize_input() File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 151, in initialize_input self.abcoff() File "/home/pi/Mycodo/mycodo/inputs/mh_z19b.py", line 199, in abcoff self.ser.write(bytearray([0xff, 0x01, 0x79, 0x00, 0x00, 0x00, 0x00, 0x00, 0x86])) File "/var/mycodo-root/env/lib/python3.7/site-packages/serial/serialposix.py", line 636, in write raise SerialTimeoutException('Write timeout') serial.serialutil.SerialTimeoutException: Write timeout

Em_Ka · May 28, 2022, 11:35am

Is /dev/ttyAMA0 the location of your serial device connected to the sensor?

i guess so. isn’t AMA0 the default location? because again, it was working via CLI - all set to default. only one UART device connected.
how would i found out if AMA0 was correct?

anyway; i now tried a cp210x usb converter with /dev/ttyUSB0 and was working directly

CaptxP · February 7, 2023, 9:59am

Hi Guys,

like many others, unfortunately I also have problems with the MH-Z19. Since many days I’ve tried everything that is on my mind, but unfortunately I do not know any further, so I would be very happy about your help.

I have the MH-Z19C-PC connected to the USB-Uart converter CP2102 as follows:
CP2102 MHZ-19
RX TX
TX RX
GND GND
VCC VCC

As input in Mycodo I used the sensor MH-Z19 (without B). Uart Device was set to /dev/ttyUSB0.

I use a Raspberry 4b.
The red LED of the sensor, which is located behind the fleece, is blinking steadily.

2023-02-07 10:56:26,039 - ERROR - mycodo.inputs.mh_z19_2fb1f0f8 - Error 101: Device not set up. See https://kizniche.github.io/Mycodo/Error-Codes#error-101 for more info.
2023-02-07 10:56:26,040 - ERROR - mycodo.controllers.controller_input_2fb1f0f8 - StopIteration raised 3 times. Possibly could not read input. Ensure it's connected properly and detected.
2023-02-07 10:56:36,747 - DEBUG - mycodo.inputs.mh_z19_2fb1f0f8 - No response
2023-02-07 10:56:36,752 - DEBUG - mycodo.controllers.controller_input_2fb1f0f8 - Adding measurements to InfluxDB with ID 2fb1f0f8-2beb-4528-be35-2718dee92226: {}
2023-02-07 10:56:41,002 - ERROR - mycodo.inputs.mh_z19_2fb1f0f8 - Error 101: Device not set up. See https://kizniche.github.io/Mycodo/Error-Codes#error-101 for more info

I’m so thankful for every help.

Regards