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Update pin-8.md #393

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Update pin-8.md
axelsimon Dec 3, 2020
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axelsimon Apr 27, 2021
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10 changes: 6 additions & 4 deletions src/en/pin/pin-8.md
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This pin doubles up as the UART transmit pin, TX. It's also commonly known as "Serial" and, by default, will output a Console from your Pi that, with a suitable Serial cable, you can use to control your Pi via the command-line.
This pin doubles up as the UART transmit pin, TX. It's also commonly known as "Serial" and, by default, will output a Console from your Pi that, with a [suitable Serial cable](https://elinux.org/RPi_Serial_Connection), you can use to control your Pi via the command line.
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I think this might not actually be the default behaviour any more (because it requires setting the SoC to a fixed clockspeed, rather than letting it turbo on demand), and you need to explicitly request this functionality using raspi-config?

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Is that so? I don't mind lying temporarily to get this merged, and then figuring this out after the fact.

I uh... have been very, very deep in RP2040 lately so my Pi know-how is rusty.

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Is that so? I don't mind lying temporarily to get this merged, and then figuring this out after the fact.

See https://www.raspberrypi.com/documentation/computers/configuration.html#interfacing-options and https://www.raspberrypi.com/documentation/computers/config_txt.html#enable_uart
(although this is often a moving target, and unfortunately the documentation isn't always kept up to date with the changes in Raspberry Pi OS)

I uh... have been very, very deep in RP2040 lately so my Pi know-how is rusty.

Nice! 😀


The UART pins are useful for setting up a "headless" Pi (a Pi without a screen) and getting it connected to a network.
The UART pins can be useful for setting up a "headless" Pi (a Pi without a screen) and getting it connected to a network.

UART can be used to talk to Serial GPS modules or sensors such as the PM5003, but you must make sure you disable the Serial Console in raspi-config first.

On the Pi 3 and 4 the UART is, by default, used for Bluetooth and you may need to add "dtoverlay=miniuart-bt" to "/boot/config.txt" to achieve a stable.
By default on the Pi 3, Pi 4 and Pi Zero W the full, hardware UART is used for Bluetooth and the Pi's UART pins are connected to the less stable miniUART. To achieve a stable UART connection to other devices, you may need to add "dtoverlay=miniuart-bt" to "/boot/config.txt". This has the effect of switching Bluetooth over to miniUART, freeing the full UART for use to connect to other devices.

Note that all UARTs are 3.3V only and damage will occur if they are connected to 5V systems.

[Learn more about UART](/pinout/uart)

[Raspberry Pi UART documentation](https://www.raspberrypi.org/documentation/configuration/uart.md)
[Raspberry Pi UART documentation](https://www.raspberrypi.org/documentation/configuration/uart.md)