DHT22 example ?

[Liberasys]

Hello Boris, Could you give an example for getting temperature and humidity from a DHT22 please ? An "import DHT" gives an error and I cannot find appropriate methods : `

import machine d = machine.DHT(machine.Pin(26)) d. readinto read DHT11 DHT2X

`

[BluSpanner]

You need to specify the type of DHT for a DHT22 use d = machine.DHT(machine.Pin(26), machine.DHT.DHT2X)

Sample code would be

import machine
pin = 26
dht = machine.DHT(machine.Pin(pin), machine.DHT.DHT2X)
result, temperature, humidity = dht.read()
if not result:
    print('Failed!')
else:
    print('t={} C'.format(temperature))
    print('h={} % RH'.format(int(humidity)))

/ David

[Liberasys]

Great thank you David, works perfectly ! :-)

[loboris]

I'm (slowly) working on finishing the Wiki documentation for all the machine modules. DHT documentation should be available soon.

@Liberasys Please close the issue, when you consider it resolved.

[Liberasys]

@loboris Thank you for the doc, it helps a lot. @BluSpanner : how did you know how to do with the loboris firmware ?

[hargathor]

@BluSpanner Thanks a lot for the example but I'm curious on how you manage to find out how to do it. It could help me on how to investigate for the next time while waiting on the documentation. Or even contributing to the doc in order to help loboris!

[BluSpanner]

Python's help() & dir() & TAB completion can be used to find out... Rather than document - here's how you can reverse-engineer... I understand that's what you want. And I'm unable to edit the wiki

Let get started...

Start with help() in the REPL

>>> help()
Welcome to LoBo MicroPython on the ESP32!

For online documentation please visit:
https://github.com/loboris/MicroPython_ESP32_psRAM_LoBo/wiki

For access to the hardware use the 'machine' module:

import machine
pin12 = machine.Pin(12, machine.Pin.OUT)
pin12.value(1)
pin13 = machine.Pin(13, machine.Pin.IN, machine.Pin.PULL_UP)
print(pin13.value())
i2c = machine.I2C(scl=machine.Pin(21), sda=machine.Pin(22))
i2c.scan()
i2c.writeto(addr, b'1234')
i2c.readfrom(addr, 4)

Basic WiFi configuration:

import network
sta_if = network.WLAN(network.STA_IF); sta_if.active(True)
sta_if.scan()                             # Scan for available access points
sta_if.connect("<AP_name>", "<password>") # Connect to an AP
sta_if.isconnected()                      # Check for successful connection

Control commands:
  CTRL-A        -- on a blank line, enter raw REPL mode
  CTRL-B        -- on a blank line, enter normal REPL mode
  CTRL-C        -- interrupt a running program
  CTRL-D        -- on a blank line, do a soft reset of the board
  CTRL-E        -- on a blank line, enter paste mode

For further help on a specific object, type help(obj)
For a list of available modules, type help('modules')

Notice the help('modules') on the last line.

Let use it to show a list of modules have been frozen into the firmware help('modules')

>>> help("modules")
__main__          json              ssl               upysh
_thread           logging           struct            urandom
array             machine           sys               ure
binascii          math              time              urequests
builtins          microWebSocket    tpcalib           uselect
cmath             microWebSrv       ubinascii         usocket
collections       microWebTemplate  ucollections      ussl
display           micropython       uctypes           ustruct
errno             network           uerrno            utime
framebuf          os                uhashlib          utimeq
freesans20        pye               uheapq            uzlib
functools         random            uio               writer
gc                re                ujson             ymodem
hashlib           select            uos               zlib
heapq             socket            upip
io                ssd1306           upip_utarfile
Plus any modules on the filesystem

module machine in the list, lets inspect it

Note there are a number of ways to do this, each method has different output...

1. help(machine)
2. dir(machine)
3. machine. then the \<TAB> key

I'll use the 3rd method,

type machine. then the \<TAB> key

>>> machine.
__name__        mem8            mem16           mem32
freq            reset           unique_id       idle
deepsleep       wake_reason     wake_description
heap_info       nvs_setint      nvs_getint      nvs_setstr
nvs_getstr      nvs_erase       nvs_erase_all   loglevel
redirectlog     restorelog      LOG_NONE        LOG_ERROR
LOG_WARN        LOG_INFO        LOG_DEBUG       LOG_VERBOSE
stdin_get       stdout_put      disable_irq     enable_irq
time_pulse_us   random          Timer           Pin
Signal          TouchPad        ADC             DAC
I2C             PWM             SPI             UART
RTC             Neopixel        DHT             Onewire
>>> machine.

Note: DHT & Pin Let explore both

>>> help(machine.DHT)
object <class 'DHT'> is of type type
  readinto -- <function>
  read -- <function>
  DHT11 -- 0
  DHT2X -- 1
>>> help(machine.Pin)
object <class 'Pin'> is of type type
  init -- <function>
  value -- <function>
  irq -- <function>
  IN -- 1
  OUT -- 3
  OPEN_DRAIN -- 7
  PULL_UP -- 0
  PULL_DOWN -- 1
  IRQ_RISING -- 1
  IRQ_FALLING -- 2
>>>

That should help provide some documentation for machine.DHT & machine.Pin

---

Now let use another approach to complete the knowledge - brute force exploration....

>>> dht = machine.DHT()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'pin' argument required
>>>

OK, machine.DHT() requires a pin

Let try with pin 4

>>> dht = machine.DHT(4)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: expecting a pin

Remember machine.Pin, let inspect it

>>> help(machine.Pin)
object <class 'Pin'> is of type type
  init -- <function>
  value -- <function>
  irq -- <function>
  IN -- 1
  OUT -- 3
  OPEN_DRAIN -- 7
  PULL_UP -- 0
  PULL_DOWN -- 1
  IRQ_RISING -- 1
  IRQ_FALLING -- 2
>>>

Let try without a value, to see what parameters are required - helpfully a pin

>>> p4 = machine.Pin()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: function missing 1 required positional arguments
>>>

Nice, it requires a value and check it

>>> machine.Pin(4)
Pin(4)

Let try it and check it

>>> dht = machine.DHT(pin=machine.Pin(4))
>>> dht
DHT(Pin=4, Type=DHT11)
>>>

Ok, it's been set to DHT11, but we want DHT22 Note: As above,

>>> help(machine.DHT)
object <class 'DHT'> is of type type
  readinto -- <function>
  read -- <function>
  DHT11 -- 0
  DHT2X -- 1
>>>

Let try with DHT22

>>> dht = machine.DHT(pin=machine.Pin(4), type=machine.DHT.DHT2X)
>>> dht
DHT(Pin=4, Type=DHT2X)

Use TAB completion

dht. `<TAB> key

>>> dht.
readinto        read            DHT11           DHT2X
>>> dht.read
readinto        read
>>> dht.read()
(True, 27.0, 47.0)

---

Expanded

import machine
p4 = machine.Pin(4)
dht_type = machine.DHT.DHT2X
dht = machine.DHT(p4, dht_type)
(success, temperature, humidity) = dht.read()

---

so altogether, with a shortened version, using positional arguments

>>> import machine
>>> machine.DHT(machine.Pin(4), machine.DHT.DHT2X).read()
(True, 26.0, 44.0)
>>> 

[hargathor]

@BluSpanner : thanks a lot for this very complete walkthrough! That's very usefull

[Liberasys]

Sorry for late response. @BluSpanner : thank you for this detailed process, it will help !