Add PulseIn to BeagleBone

Installed these libraries on my Beaglebone Black

pip3 install adafruit-blinka pip3 install adafruit-circuitpython-dht

Running this test code (Python 3.5)

import time
import board
import adafruit_dht

# Initial the dht device, with data pin connected to:
dhtDevice = adafruit_dht.DHT22(board.P8_11)

while True:
    try:
        # Print the values to the serial port
        temperature_c = dhtDevice.temperature
        temperature_f = temperature_c * (9 / 5) + 32
        humidity = dhtDevice.humidity
        print("Temp: {:.1f} F / {:.1f} C    Humidity: {}% "
              .format(temperature_f, temperature_c, humidity))

    except RuntimeError as error:
        # Errors happen fairly often, DHT's are hard to read, just keep going
        print(error.args[0])

    time.sleep(2.0)

Getting this message

Traceback (most recent call last): File “/var/lib/cloud9/Python/dht_simpletst.py”, line 6, in <module> dhtDevice = adafruit_dht.DHT22(board.P8_11) File “/usr/local/lib/python3.5/dist-packages/adafruit_dht.py”, line 255, in init super().init(False, pin, 1000) File “/usr/local/lib/python3.5/dist-packages/adafruit_dht.py”, line 66, in init self.pulse_in = pulseio.PulseIn(self._pin, 81, True) AttributeError: module ‘pulseio’ has no attribute ‘PulseIn’

Beaglebone Black Debian/Linux versions

BeagleBoard.org Debian Image 2018-03-05 Linux beaglebone 4.9.82-ti-r102 #1 SMP PREEMPT Thu Feb 22 01:16:12 UTC 2018 armv Debian GNU/Linux 9 (stretch)

Blinka test code works

import board
import digitalio
import busio

print("Hello blinka!")

# Try to create a Digital input
pin = digitalio.DigitalInOut(board.P8_11)
print("Digital IO ok!")

# Try to create an I2C device
i2c = busio.I2C(board.SCL, board.SDA)
print("I2C ok!")

# Try to create an SPI device
spi = busio.SPI(board.SCLK, board.MOSI, board.MISO)
print("SPI ok!")

print("done!")

Hello blinka! Digital IO ok! I2C ok! SPI ok! done!

The instructions I am following

https://learn.adafruit.com/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging?view=all

[jrobparsons]

Yes. I would like to add it. I will start looking at the code.

On Mon, Jul 22, 2019, 7:43 PM Melissa LeBlanc-Williams < [e-mail]> wrote:

Most likely this is because the BBB board hasn’t had PulseIn added yet, whereas the Raspberry Pi has. Are you interested in adding it?

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/adafruit/Adafruit_Blinka/issues/140?email_source=notifications&email_token=AAVRFUAVFI3ZKHHD5T6HHKLQAZAZJA5CNFSM4IF5635KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD2RPGGI#issuecomment-513995545, or mute the thread https://github.com/notifications/unsubscribe-auth/AAVRFUF5TN6BCSZMLBNYMULQAZAZJANCNFSM4IF5635A .

[jrobparsons]

Took a major side-trip into understanding device tree overlay and loadable kernel module development…

1. The sysfs/libgpiod playground

In order to free up a pin for use by libgpiod_pulseio (via libgpiod interface) and leave pins for use by Adafruit_* modules (via sysfs interface), the universal cape overlay that is loaded during boot-up must be edited, compiled, then copied back into /lib/firmware where available for next boot-up.

In my system, the overlay being loaded is,

univ-bbb-EVA-00A0.dtbo univ-bbb-EVx-00A0.dtbo univ-bbb-Exx-00A0.dtbo univ-bbb-xVA-00A0.dtbo univ-bbb-xVx-00A0.dtbo univ-bbb-xxx-00A0.dtbo

and is determined by my /boot/uEnv.txt configuration.

I edited the corresponding DTS file in “/opt/source/bb.org-overlays/src/arm/”, compiled it using “/opt/source/bb.org-overlays/make src/arm/univ-bbb-Exx-00A0.dtbo”, then copied the DTBO file to “/lib/firmware”.

I edited the DTS file by disabling all configuration of pin P8_11 (the one used in the dht_simpletst.py example) by following what was done to disable pins P9_19 and P9_20 (the pins supporting the cape I2C EEPROM bus).

Now…

Both “blinkatest.py” and “dht_simpletst.py” run successfully.

2. libgpiod_pulseio CPU hog!!

I am running “dht_simpletst.py” with a 10 second sleep between attempts to read temperature and humidity.

The CPU utilization by libgpiod_pulseio remains pegged at a constant 98% even while the python program is sleeping!

top - 14:04:35 up 32 min,  2 users,  load average: 1.17, 0.84, 0.67
Tasks: 102 total,   2 running, 100 sleeping,   0 stopped,   0 zombie
%Cpu(s): 19.5 us, 80.5 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :   495588 total,   274928 free,   110764 used,   109896 buff/cache
KiB Swap:        0 total,        0 free,        0 used.   367568 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
 1822 debian    20   0    1448    976    904 R 97.1  0.2   0:53.91 libgpiod_pulsei
 1772 debian    20   0    7192   2900   2344 R  1.6  0.6   0:03.28 top
 1821 debian    20   0   13104   9328   5580 S  1.0  1.9   0:00.94 python
    4 root      20   0       0      0      0 D  0.3  0.0   0:13.51 kworker/0:0
  821 www-data  20   0  228992   3172   1780 S  0.3  0.6   0:02.00 apache2
 1491 root      20   0       0      0      0 S  0.3  0.0   0:00.46 kworker/0:2
    1 root      20   0   25496   5000   3904 S  0.0  1.0   0:03.42 systemd

More later…