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Here is what I am trying to do: log on to linux running on a raspberry pi zero 2 W. But I also want to use the "real" UART PL011 (NOT the mini uart) for RS485 (modbus) at the same time.

On the arduino I had used previously I could use SoftwareSerial to get an extra serial port which worked reliably. I have to run the UART at 9600 baud 8 bit no parity 1 stop bit CRC. I suppose if the mini uart worked okay that would be acceptable but worse. The biggest problem is I keep reading

"The bluetooth/wireless module is disabled when you enable the PL011"

but no one says if the wifi specifically is disabled. I would try it but I am afraid to brick it due to the chip shortage. I found https://github.com/raspberrypi/documentation/blob/develop/documentation/asciidoc/computers/configuration/uart.adoc. Also if the linux console was previously on the PL011 (pins GPIO14,GPIO15) could I even log on at all or even brick the darn thing?

Is there some standard documentation I have not found yet? recommendation? thanx. I have no interest in bluetooth but would very much like to log on to the thing somehow preferably wifi and usb/serial as a backup.

William Garber
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1 Answers1

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See How do I make serial work on the Raspberry Pi3 or later - specifically
"Finally if you don't use Bluetooth (or have undemanding uses) it is possible to swap the ports back in Device Tree. There is a miniuart-bt and disable-bt module which are described in /boot/overlays/README."

dtoverlay -h miniuart-bt will show help for miniuart-bt

NOTHING you can do in software will "brick the darn thing"

Milliways
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  • This answer is still correct, and explains in more detail the nature of the changes, but most users of current Raspbian should just run sudo raspi-config Select Interfacing Options / Serial then specify if you want a Serial console (probably no) then if you want the Serial Port hardware enabled (probably yes). Then use /dev/serial0 in any code which accesses the Serial Port. – William Garber May 26 '22 at 02:21
  • This is probably what I want, not a console, just serial hardware for my RS485 MAX485 breakout/chip to connect to. If I did this would it stop me from using wifi to ssh on to the raspberry pi? Can you still use usb devices on the data usb port with a usb otg cable? Could I still use ttyUSB on the data usb port? – William Garber May 26 '22 at 02:29
  • sorry the first comment is a quote from the web page you linked to – William Garber May 26 '22 at 02:34
  • @WilliamGarber I don't know where you got the idea about WiFi; the linked answer is quite clear. Why don't you just try it? – Milliways May 26 '22 at 03:01
  • I just tried it. I just used the "raspi-config" utility. They changed the option, however. Now it is under "interface". After the change I could still connect by ssh over wifi and my usb keyboard and mouse still work. Do not know about ttyUSB. I only bought the raspberry pi two days ago. – William Garber May 26 '22 at 03:08