rs232 to rs485 conversion

[travelo94]

hi im using uart on pico with rs232 converter now i want to use rs485 ,
i wrote some demo code on rs232 that works.
`from machine import UART, Pin
import machine
uart=(0, baudrate=9600, bits=8, parity=None, stop=1, tx=Pin(0), rx=Pin(1), txbuf=256, rxbuf=256, timeout=2000)
data=[0x00,0x01]
uart.write(bytes(data))
uart.read()

`
do i have to change anything to use rs485? beacuse when i connected circuit it didnt worked

[karfas]

beacuse when i connected circuit it didnt worked

... is hardly a problem description someone can work with.

You know that RS232/RS458/UART are completely different things electrically ?

[travelo94]

i use waveshare 4738
I added the uart.flush() i got error AttributeError: UART object has no attribute 'flush'
same error with txdone()

[robert-hh]

Please update the firmware to a recent daily build. uart.flush() was added after v1.19.1.

[robert-hh]

Script updated, not using UART 0 and pins 0 and 1, which does not work here

from machine import UART, Pin
import machine
uart=UART(1, baudrate=9600, bits=8, parity=None, stop=1, tx=4, rx=5, txbuf=256, rxbuf=256, timeout=2000) 
rse=Pin(15, Pin.OUT)
data=[0x00,0x01]
rse.high()
uart.write(bytes(data))
uart.flush()  # Added to wait for the data being sent
rse.low()
uart.read()

[travelo94]

i use thonny 4.0.1 there is no newer version

[robert-hh]

I talked about the firmware of the ESP32 board, and you do not need thonny top update it. The fESP32 firmware is at https://micropython.org/download/?port=esp32 together with update instructions. if you use Windows or MAC OSx, you have to use a different USB port name.

[robert-hh]

Glancing into Thonny I see, that you can use it to update the ESP32 firmware, after having downloaded the proper version.

[robert-hh]

Seems similar. Did you connect rse to GPIO15, which is board pin 20, or to board pin 15?

[robert-hh]

The delay must be just right, otherwise the received data is lost. You can try small changes using sleep_us().

[robert-hh]

GPIO4 is board pin 6, GPIO5 is board pin 7. Micropython uses GPIO numbers, not board pin numbers,

[travelo94]

ye the gpio15 the last one on the left side i was even checking and added led to see if the state is changing
checked all delays from 100us to 3000 and still

[karfas]

I would check on hardware level where the signal gets lost.
Just add a LED (maybe with an resistor)

• from UART tx to ground
• between input of the RS485 to ground
• between the RS485 lines

You will see the led flickering when you send data and/or see it flickering in a different way when one of the attached devices returns something on the RS485 bus.