Currently VoCore2 do not have reset button, so some beginners are hard to reset the firmware once it is bricked by wrong setting…
This new patch of uboot is used to solve that, it is much easier than upload firmware from serial port, but maybe still hard for beginner.
If you want to have a try of the new uboot, please download from vonger.cn/misc/vocore2/uboot128m.20190808.bin (Lite version please use uboot64m.20190808.bin, or it will failed to boot).
You can use exists uboot on vocore, choose 7 to upload new uboot to VoCore2 by serial port(kermit protocol)
To active first boot from uboot, you need to connect I2C_SD pin(GPIO5) to GND then power on your VoCore2. Another way is in uboot menu, press ‘r’, then it will reset firmware automatically, this way need serial port, not that simple like first way.
VoCore2 wifi LED will flash quickly (0.07s/0.1s), means you have entry reset mode, then disconnect I2C_SD pin from GND, the flash speed will slow down(1s/1s), that means we are erasing the NOR flash. Around 3 minutes, it stops flashing, the reset is done.
Here is the patch(modify board.c only), you can download full patch from https://github.com/Vonger/uboot/blob/master/uboot-20190808.patch
How it works?
I2C_SD pin has a pull-up resistor, so we can use it as a ‘button’.
- once boot up, uboot will set I2C_SD into GPIO input mode and check its value. If it is 1, means we should boot normally, button is not pressed; if it is 0, means ‘button’ is pressed, we should go to reset mode.
- in reset mode, we flash the wifi led quickly to notify user we are ready to reset. Once user disconnect I2C_SD to GND (release the button), we are ready to erase the flash.
- We need to keep firmware just reset user data, and user data is in rootfs_data partition. So in order to find the partition position, we have to use a tricky, because rootfs_data is jffs2 disk format, we just need to find its magic code at every 0x10000 bytes. Once we find its start position, we can easily use SPI command to erase the flash rootfs_data.
- finally, start linux. It will do rest. 🙂