Add simple UART bootloader example #571
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bootloaders/uart/uart_boot.c
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| #define UART_ID uart1 | ||
| #define BAUD_RATE 1000000 |
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The baud-rate is hardcoded in uart_binary.c (because I assume that it can't be changed, as it's the baud-rate required by the bootrom) so should it also be hardcoded (rather than being a #define) in uart_boot.c too?
Although I guess that the uart-bootloader baud rate could theoretically be different to the post-boot application baud rate (IYSWIM); so I wonder if having them deliberately different might make this a more interesting example? 🤔
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Yes, it should be hardcoded in both - I've fixed that
If the post-boot application used a different baud rate, then it wouldn't be able to boot the board again if it's power cycled - this way you can power cycle the separate device and watch the bootloader run again without rebooting the main device
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Yeah, I was assuming that in order to accommodate my suggestion, the code (in the main device) would need to dynamically reconfigure the baud rate at the start and end of the uart-boot sequence 🙂
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I wonder if things like the "splash string", the "knock sequence", the "uart-bootloader baudrate", etc. ought to be defined in a header-file somewhere in EDIT: Ah, perhaps https://github.com/raspberrypi/pico-sdk/blob/develop/src/rp2_common/boot_bootrom_headers/include/boot/bootrom_constants.h would be a good place for those 🙂 |
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This worked well for me once I'd figured out that the uart binary had to be loaded into the "master" device first. It would be more fun if the binary could be built into a header file to avoid that step |
The sample binary flashes the LED and prints Hello, world back over the UART interface
Add a UART bootloader example, which reads a binary from the partition table on the main device, and uses the UART bootloader to boot that binary on a separate device. Requires a modified separate board to run, as you need access to the QSPI pins to use them as UARTs for the bootloader (see 5.8 in the datasheet) - the main board can be a normal RP2350 board.
This sample binary flashes the LED and prints "Hello, world" back over the UART interface, which demonstrates setting up QSPI GPIOs as UARTs.