Change the target to Beaglebone Black

[neocafe88]

Change the target to the hardware board.

DoD: Program the board successfully and the embedded system report the temperatures to AWS IoT like it did in QEMU.

Blocker: None

[neocafe88]

Build log:

• Don't use the Linux patch provided in board/beaglebone/ which is set in the beaglebone_defconfig in BR2_GLOBAL_PATCH_DIR
• U-Boot version: 2021.04 -- other version causes an error: kwimage.c, some function argument conflict.
• The toolchain downloaded from the ARM developer site doesn't work as the directory structure doesn't meet required by Buildroot.

Build was successful.

[neocafe88]

Flashing Notes:

• Good Guide: https://bootlin.com/doc/training/buildroot/buildroot-labs.pdf
• It seems Mac OS is not a good platform to flash the SD card. First of all, it can't read ext4. Also it doesn't have a good partition tool at bat. Ended up using BeagleBone black itself for flashing the SD card.
• The Linux on the BeagleBone Black's onboard memory is a full suite.
• Using Beaglebone Black to flash the SD card makes it a better workflow. The steps go:
  • Boot with the on-board OS
  • Insert SD card, partition it.
  • Download images from the dev host
  • Flash the images on to SD card
  • Power down
  • Boot with the boot button to boot from SD card

The booting from the Buildroot-built embedded Linux worked:

[neocafe88]

The MQTT client ('temp sensor') didn't work because the date/time in the embedded system was Jan 1 2000 (TLS negotiation fails). When it is set correctly, it began to work.

[neocafe88]

DoD is verified as BBB successfully read the temperature from the pseudo temperature driver and published to AWS IoT Core successfully. And the AWS IoT Core distributed the messages to a subscribing client.