MicroPython Forum (Archive)

Hi guys,

does anyone know that or can give a hint?
I want to use the DS3231 and the DHT22 on the ESP8266-01, there I have the following Pins available:

Pin 0
Pin 1 (UART - TX)
Pin 2
Pin 3 (UART - RX)

Normally for measuring the temperature and maybe control the chip I need one Pin for the DHT22 signal, and two Pins for the I2C and if possible one Pin for the UART - TX functionality.
Can you answer if it is possible:

to use the Pins 1 and 3 for I2C functionality
only to make the TX functionality Pin available on Pin 2 for example
and use the DHT on Pin 0

If possible can you say how to set up the Pin config fot the UART?

PS: using this Adapter: http://esp8266-01-adapter.de/

Thank you
Frank

I can’t test it right now, but from memory:

• You cannot reconfigure the pins of UART 0 because they are hardwired, however what you want to do should be possible using UART 1, which transmits on GPIO2 (and cannot receive). To switch the terminal output to a different UART, use uos.dupterm().
• I2C and DHT should work on all pins because they are implemented in software.
• Make sure you can still pull up and down pins 0 and 2 as required for booting.

Hi thank you for your post,

but as I know in Arduino you can disable the Serial and so use for example all 4 GPIO pins on the ESP8266-01 for reading sensors.
So I thought this should also be able with micropython.
Isn't it?

I probably misunderstood what you meant by “reconfigure”. What I’m saying is that you cannot use other pins than 1 and 3 for UART 0. However, you should indeed be able to use pins 1 and 3 for other purposes than UART 0.

(If there is anything else to discuss, let’s continue in the other topic you opened in the proper forum.)

Not necessarily.

The ESP8266's that have an onboard USB-to-serial adapter on them have the TX line from the USB-to-serial converter hard wired to the RX pin on UART0, so if you try to use that physical pin for a different purpose then you'll have 2 sources trying to drive the pin, and you won't get what you expect.

Of course, if you're using a module with no USB-to-serial converter then you're free to use the pin for something else.

Now some boards, like the NodeMCU board
https://circuits4you.com/wp-content/upl ... iagram.png
may have inline resistors (470 ohms in the schematic above) which means that you would be able to use the RX line for a low-impedance source (something which has a significantly lower impedance than 470 ohms). When no data is being received then the 470 ohm resistor will act like a 470 ohm pullup (since the UART idle state is high), but when data comes into, then it will oscillate back and forth between acting like a pullup and pulldown.

Good point (and that was also the reason why I still haven’t tested it). I was specifically referring to the OP’s ESP-01 module, which does not include a USB-to-serial converter.