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Board Support Packages

Today we're introducing the notion of Board Support Packages (BSPs) to the moxie toolchain.

A BSP provides all of the configuration data and code requires to target a specific hardware platform. This mostly involves linker scripts, platform initialization code, and hardware abstraction support libraries.

Until recently the gdb sim was our only target platform. Now we also have qemu, which needs to use an alternate _write implementation in order to send output to a memory mapped UART. What we really need to do is to define a "qemu" BSP that targets the default "board" defined in qemu. This BSP will provide a support library with the UART version of _write, and the original gdb sim version will live in a "sim" BSP.

In the world of the GNU toolchain, BSPs live in libgloss. The libgloss tree now contains BSP specific linker scripts which you must use in order to pull in either of the BSP support libraries needed by newlib. So if you want to target qemu, you run...

$ moxie-elf-gcc -o hello.x hello.c -Tqemu.ld

..and if you want to target the gdb sim, you have to go...

$ moxie-elf-gcc -o hello.x hello.c -Tsim.ld

This will make more sense down the line as we add more target boards with different memory maps and peripherals.

Speaking of peripherals.... I've also added a Real Time Clock device to the qemu board definition which I'll talk about in my next posting.

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