Returns null - Need help #26

OlafKocanda · 2020-12-13T14:33:34Z

Hi there,

first of all thank you for your package. I have recently started playing around with a rpi 4 and wanted to connect a mh-z19b with your python package.

I made sure the serials are available:

serial0 -> ttyS0
serial1 -> ttyAMA0

Enabled i2c
However i2c output is empty

And even made sure uart is enabled (as seen on another blog )

When I run sudo python -m mh_z19 I (most of the time) get back
null

Sometimes, however there is also another message:

Here is my cabling set up.

I should mention, that the soldered pins at the mh-z19b where bent a bit due to delivery. But I don't think (hope) this is a problem.

Do you have any ideas what else I could test to make it work?

Thanks in advance!

The text was updated successfully, but these errors were encountered:

nincube8 · 2020-12-13T17:20:19Z

You need a 1-5k Ohm resistor between Vcc+ and TxD line.

…

On Sun, Dec 13, 2020 at 7:33 AM Olaf Kocanda ***@***.***> wrote: Hi there, first of all thank you for your package. I have recently started playing around with a rpi 4 and wanted to connect a mh-z19b with your python package. I made sure the serials are available: serial0 -> ttyS0 serial1 -> ttyAMA0 Enabled i2c However i2c output is empty And even made sure uart is enabled (as seen on another blog <https://www.circuits.dk/testing-mh-z19-ndir-co2-sensor-module/> ) When I run sudo python -m mh_z19 I (most of the time) get back null Sometimes, however there is also another message: [image: IMG_1122] <https://user-images.githubusercontent.com/58265203/102014806-2f01de00-3d58-11eb-9cfc-5378564dfbaa.jpg> Here is my cabling set up. [image: IMG_0623] <https://user-images.githubusercontent.com/58265203/102014588-ff9ea180-3d56-11eb-8034-541b22045080.jpg> [image: IMG_0625] <https://user-images.githubusercontent.com/58265203/102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a.jpg> I should mention, that the soldered pins at the mh-z19b where bent a bit due to delivery. But I don't think (hope) this is a problem. Do you have any ideas what else I could test to make it work? Thanks in advance! — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#26>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEBLRRP2TBJDGLG3JTPUAMTSUTGEVANCNFSM4UZRETAA> .

OlafKocanda · 2020-12-14T08:29:07Z

Hi nincube8,

Thanks a lot for your answer!
Could you explain a bit what you mean by Vcc+ and TxD line?

Do you want me to put a resistor going from the Vin to the Tx on the MH-Z19B?

nincube8 · 2020-12-14T08:41:43Z

You should be able to see the unit light up through the white box on the side. Usually it's the transfer packet clock that needs a resistor (Tx = Transfer) between the (Vcc 3v) to be able to decode the strings received by the unit correctly. The (RxD = Receive line) doesn't need the resistor.

…

On Mon, Dec 14, 2020 at 1:29 AM Olaf Kocanda ***@***.***> wrote: Hi nincube8, could you explain a bit what you mean by Vcc+ and TxD line? Do you want me to put a resistor going from the Vin to the Tx on the MH-Z19B? [image: 102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a] <https://user-images.githubusercontent.com/58265203/102057757-b39f3b80-3dee-11eb-96dd-8be0933ce8c2.jpg> — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#26 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEBLRRJTPYCLRW7CJZBTVDLSUXEGDANCNFSM4UZRETAA> .

nincube8 · 2020-12-14T08:43:18Z

I believe this unit is a 5 Volt unit and requires the 5 volt rail on your Device or Microcomputer. On Mon, Dec 14, 2020 at 1:41 AM CK Gaming Channel <cevatkose@gmail.com> wrote:

…

You should be able to see the unit light up through the white box on the side. Usually it's the transfer packet clock that needs a resistor (Tx = Transfer) between the (Vcc 3v) to be able to decode the strings received by the unit correctly. The (RxD = Receive line) doesn't need the resistor. On Mon, Dec 14, 2020 at 1:29 AM Olaf Kocanda ***@***.***> wrote: > Hi nincube8, > > could you explain a bit what you mean by Vcc+ and TxD line? > > Do you want me to put a resistor going from the Vin to the Tx on the > MH-Z19B? > [image: 102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a] > <https://user-images.githubusercontent.com/58265203/102057757-b39f3b80-3dee-11eb-96dd-8be0933ce8c2.jpg> > > — > You are receiving this because you commented. > Reply to this email directly, view it on GitHub > <#26 (comment)>, > or unsubscribe > <https://github.com/notifications/unsubscribe-auth/AEBLRRJTPYCLRW7CJZBTVDLSUXEGDANCNFSM4UZRETAA> > . >

OlafKocanda · 2020-12-14T08:52:06Z

just to make sure: The MH-Z19B is connected to the 5v pin on my raspberry.

Shouldn't the light be on if it receives enough power without any further resistors?

nincube8 · 2020-12-14T09:07:16Z

Yes, that is correct.

…

On Mon, Dec 14, 2020 at 1:52 AM Olaf Kocanda ***@***.***> wrote: just to make sure: The MH-Z19B is connected to the 5v pin on my raspberry. Shouldn't the light be on if it receives enough power without any further resistors? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#26 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEBLRRPQHHGEOREQWQ6OE7DSUXG4LANCNFSM4UZRETAA> .

OlafKocanda · 2020-12-14T09:08:45Z

Thanks!

Well, then I believe there is something else I am missing here to make it work...

DoudouHirofumi · 2021-01-03T11:17:37Z

Hi there.
I had the same problem.
Please try to install "i2c-tools".
sudo apt install i2c-tools

After installing it, the "null" problem was solved.

mazdafunsunn · 2021-01-04T18:16:25Z

I have same problem. will try to solder.
i2c-tools was already installed.
red LED is blinking.

smrt28 · 2021-01-05T16:59:40Z

I had the same issue. I added:

[all]
enable_uart=1
core_freq=250

to /boot/config.txt, reboot and /dev/serial0 works.

mazdafunsunn · 2021-01-06T09:50:33Z

I had the same issue. I added:
[all]
enable_uart=1
core_freq=250
to /boot/config.txt, reboot and /dev/serial0 works.

This worked for me as well.

UedaTakeyuki · 2021-01-19T22:46:38Z

no feedback

flipper31 · 2021-02-03T14:20:05Z

I put a 1k Ohm resistor between Tx and Vin still Null then I Tried 3k Ohm but still null every other solution like fix core_freq to 250 are not working aswell. :/ Do you have any ideas to solve this problem ?

mohshbool · 2021-02-08T07:38:44Z

I put a 1k Ohm resistor between Tx and Vin still Null then I Tried 3k Ohm but still null every other solution like fix core_freq to 250 are not working aswell. :/ Do you have any ideas to solve this problem ?

im having the same problem as you man. pi 4b

UedaTakeyuki · 2021-02-09T08:01:00Z

How about using PWM interface?

https://github.com/UedaTakeyuki/mh-z19#pwm-support

mohshbool · 2021-02-09T14:50:48Z

How about using PWM interface?

https://github.com/UedaTakeyuki/mh-z19#pwm-support

i tried that man, i connected the pwm on the sensor to gpio12, gpio26 and gpio 16 (which is the fifth one from the top right)
here's what gpio readall shows:

 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 |     |     |    3.3v |      |   |  1 || 2  |   |      | 5v      |     |     |
 |   2 |   8 |   SDA.1 |   IN | 1 |  3 || 4  |   |      | 5v      |     |     |
 |   3 |   9 |   SCL.1 |   IN | 1 |  5 || 6  |   |      | 0v      |     |     |
 |   4 |   7 | GPIO. 7 |   IN | 1 |  7 || 8  | 1 | ALT5 | TxD     | 15  | 14  |
 |     |     |      0v |      |   |  9 || 10 | 1 | ALT5 | RxD     | 16  | 15  |
 |  17 |   0 | GPIO. 0 |   IN | 0 | 11 || 12 | 0 | IN   | GPIO. 1 | 1   | 18  |
 |  27 |   2 | GPIO. 2 |   IN | 1 | 13 || 14 |   |      | 0v      |     |     |
 |  22 |   3 | GPIO. 3 |   IN | 0 | 15 || 16 | 0 | IN   | GPIO. 4 | 4   | 23  |
 |     |     |    3.3v |      |   | 17 || 18 | 0 | IN   | GPIO. 5 | 5   | 24  |
 |  10 |  12 |    MOSI |   IN | 0 | 19 || 20 |   |      | 0v      |     |     |
 |   9 |  13 |    MISO |   IN | 0 | 21 || 22 | 0 | IN   | GPIO. 6 | 6   | 25  |
 |  11 |  14 |    SCLK |   IN | 0 | 23 || 24 | 1 | IN   | CE0     | 10  | 8   |
 |     |     |      0v |      |   | 25 || 26 | 1 | IN   | CE1     | 11  | 7   |
 |   0 |  30 |   SDA.0 |   IN | 1 | 27 || 28 | 1 | IN   | SCL.0   | 31  | 1   |
 |   5 |  21 | GPIO.21 |   IN | 1 | 29 || 30 |   |      | 0v      |     |     |
 |   6 |  22 | GPIO.22 |   IN | 1 | 31 || 32 | 1 | IN   | GPIO.26 | 26  | 12  |
 |  13 |  23 | GPIO.23 |   IN | 0 | 33 || 34 |   |      | 0v      |     |     |
 |  19 |  24 | GPIO.24 |   IN | 0 | 35 || 36 | 0 | IN   | GPIO.27 | 27  | 16  |
 |  26 |  25 | GPIO.25 |   IN | 0 | 37 || 38 | 0 | IN   | GPIO.28 | 28  | 20  |
 |     |     |      0v |      |   | 39 || 40 | 0 | IN   | GPIO.29 | 29  | 21  |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+

and here's the error im getting

pi@raspberrypi:~ $ python -m mh_z19 --pwm --pwm_gpio 12 --pwm_range 2000
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/home/pi/.local/lib/python2.7/site-packages/mh_z19/__main__.py", line 101, in <module>
    print mh_z19.read_from_pwm(gpio=args.pwm_gpio, range=args.pwm_range, )
  File "/home/pi/.local/lib/python2.7/site-packages/mh_z19/__init__.py", line 213, in read_from_pwm
    raise GPIO_Edge_Timeout("gpio {} edge timeout".format(gpio))
mh_z19.__init__.GPIO_Edge_Timeout: gpio 12 edge timeout

UedaTakeyuki · 2021-02-10T09:24:24Z

For PWM, connect with 3 lines: 5V, GND, and signal line(Fx: gpio12).
refer https://github.com/UedaTakeyuki/mh-z19/wiki/PWM-support.#cabling

OlafKocanda changed the title ~~Returns null - Need help!,~~ Returns null - Need help Dec 13, 2020

UedaTakeyuki closed this as completed Jan 19, 2021

UedaTakeyuki mentioned this issue Feb 3, 2021

sudo python -m mh_z19 alway returns null #28

Closed

UedaTakeyuki mentioned this issue Oct 4, 2021

"null" on screen. #32

Closed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Returns null - Need help #26

Returns null - Need help #26

OlafKocanda commented Dec 13, 2020

nincube8 commented Dec 13, 2020 via email

OlafKocanda commented Dec 14, 2020 •

edited

Loading

nincube8 commented Dec 14, 2020 via email

nincube8 commented Dec 14, 2020 via email

OlafKocanda commented Dec 14, 2020

nincube8 commented Dec 14, 2020 via email

OlafKocanda commented Dec 14, 2020

DoudouHirofumi commented Jan 3, 2021

mazdafunsunn commented Jan 4, 2021

smrt28 commented Jan 5, 2021

mazdafunsunn commented Jan 6, 2021

UedaTakeyuki commented Jan 19, 2021

flipper31 commented Feb 3, 2021

mohshbool commented Feb 8, 2021

UedaTakeyuki commented Feb 9, 2021

mohshbool commented Feb 9, 2021

UedaTakeyuki commented Feb 10, 2021

Returns null - Need help #26

Returns null - Need help #26

Comments

OlafKocanda commented Dec 13, 2020

nincube8 commented Dec 13, 2020 via email

OlafKocanda commented Dec 14, 2020 • edited Loading

nincube8 commented Dec 14, 2020 via email

nincube8 commented Dec 14, 2020 via email

OlafKocanda commented Dec 14, 2020

nincube8 commented Dec 14, 2020 via email

OlafKocanda commented Dec 14, 2020

DoudouHirofumi commented Jan 3, 2021

mazdafunsunn commented Jan 4, 2021

smrt28 commented Jan 5, 2021

mazdafunsunn commented Jan 6, 2021

UedaTakeyuki commented Jan 19, 2021

flipper31 commented Feb 3, 2021

mohshbool commented Feb 8, 2021

UedaTakeyuki commented Feb 9, 2021

mohshbool commented Feb 9, 2021

UedaTakeyuki commented Feb 10, 2021

OlafKocanda commented Dec 14, 2020 •

edited

Loading