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babbleberry / rpi4-osdev

Tutorial: Writing a "bare metal" operating system for Raspberry Pi 4
https://www.rpi4os.com
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Part3 update, a better(maybe) way to edit config.txt #11

Closed fishjump closed 3 years ago

fishjump commented 3 years ago

Hi, there

As I want to figure out why the CPU frequency number that makes UART work is 500Mhz, I found an official webpage https://www.raspberrypi.org/documentation/configuration/uart.md, and by following this guide, use enable_uart=1 instead of core_freq_min=500 can be a better solution.

BR

babbleberry commented 3 years ago

Thanks for this. It took me a while to get my head around how the UARTs are setup on RPi4 (the documentation is notoriously confusing).

Your solution will likely work, but only if you don't want to have UART (on GPIO pins) and Bluetooth access simultaneously (and we go on to implement Bluetooth later in the tutorial). As far as I recall, that will require the setup I have here.

Do let me know if you discover differently though!

BR, Adam

fishjump commented 3 years ago

Hi,

I double-checked the official guide, I'm not sure enable_uart=1 is going to disable Bluetooth and set miniUART to secondary UART or just adjust CPU frequency. The guide does not talk in much detail about this. Anyway, thanks for your reply and I'll close this PR.

BR