先长按住Pico 开发板上的 BOOTSEL 按钮（一直按住不松），在将 Pico 用USB线 插入到电脑的USB接口，最后松开 BOOTSEL 按钮。 这时电脑上会出现个磁盘名为：RPI-RP2 类似插入U盘的效果。 

在你电脑ubuntu linux系统安装picotool
然后在linux的终端使用picotool烧录固件。

psram-bootloader.uf2是类似BIOS / 引导加载器，先使用以下命令刷 uf2文件
sudo picotool load -fu psram-bootloader.uf2

再使用以下命令刷入Linux 系统镜像：
sudo picotool load -fxup 0 flash-image.bin

使用USB转串口工具，UART-RX接pico2的GPIO0，UART-TX引脚接pico2的GPIO1。
打开串口终端能够进入linux终端即可（此系统为linux最小系统裁剪版本buildroot，内核是6.10）

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First, press and hold the BOOTSEL button on the Pico development board (keep it pressed), then plug the Pico into a USB port on your computer using a USB cable. Finally, release the BOOTSEL button. A disk named "RPI-RP2" will appear on your computer, similar to inserting a USB flash drive.

Install picotool on your Ubuntu Linux system.
Then use picotool in the Linux terminal to flash the firmware.

psram-bootloader.uf2 is similar to a BIOS/boot loader. First, flash the uf2 file using the following command:
sudo picotool load -fu psram-bootloader.uf2

Then flash the Linux system image using the following command:
sudo picotool load -fxup 0 flash-image.bin

Use a USB-to-serial converter to connect UART-RX to GPIO0 on the Pico2 and UART-TX to GPIO1 on the Pico2.
Open the serial terminal to access the Linux terminal (this system is a minimal Linux system, builtroot, with kernel 6.10).