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Raspberrypi 3でUART通信する際の課題と解決方法

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Raspberrypi 3でUART通信する際の課題

Raspberrypi 2以前では使用できていたUARTがそのままでは使えない.



The baud rate of the mini UART is linked to the core frequency of the VPU on the VC4 GPU. This means that as the VPU frequency governor varies the core frequency, the baud rate of the UART also changes. This makes the UART of limited use in the default state. Also, when the linux console uses the mini UART (Raspberry Pi 3, Raspberry Pi Zero W), as a consequence of the UART being disabled, the console is also disabled.




1. クロックを固定する

The Linux console can be re-enabled by adding enable_uart=1 to config.txt. This also fixes the core_freq to 250Mhz (unless force_turbo is set, when it will fixed to 400Mhz), which means that the UART baud rate stays consistent.

2. Bluetoothに割り当てていたPL011をUARTに割り当てる



いずれの場合においても /dev/serial0を通してUART通信することに注意.

The primary UART is that assigned to the Linux console, which depends on the Raspberry Pi model as described above, and can be accessed via /dev/serial0.

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