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A minimum preemptive OS on Cortex-M3 (specially on blue-pill board) written in Rust. It is for the purpose ofresearching and showing how the fundamental runtime of Cortex-M3 works.

In computing, preemption is the act of temporarily interrupting a task being carried out by a computer system,without requiring its cooperation, and with the intention of resuming the task at a later time. Such changes ofthe executed task are known as context switches. ---- Wikipedia

In breif, the kernel of non-preemptive OS can not interrupt a task, while the kernel of preemptive OS can takethe control back without informing the task.

• Make sure you have ablue-pill board and a serial port reciever.
• Make sure you havearm-none-eabi toolchain andopenocd installed on your platform.
• Install the latest nightly rust toolchain. The compiler version used when this project is beening written isrustc 1.37.0-nightly (17e62f77f 2019-07-01).

This project is collections of several stages of building a preliminary preemptive OS from sketch. I'll makesure all code of each chapter can compile and run onblue-pill.

• EnterChapter5-MultiTasking

cd Chapter5-MultiTasking

• Connect theblue-pill to your laptop.

• Connect pinPA2 to a serial reciever, with 115200 baudrate, 8 data bits, 1 stop bits, no parity and no flow control.

• Runopenocd:

> openocd...Info : using stlink api v2Info : Target voltage: 3.175214Info : stm32f1x.cpu: hardware has 6 breakpoints, 4 watchpoints

• Run the application:

> cargo run    Finished dev [unoptimized + debuginfo] target(s) in 0.93s    Running `target\thumbv7m-none-eabi\debug\preemptive`Reading symbols from target\thumbv7m-none-eabi\debug\preemptive...done.target halted due to debug-request, current mode: ThreadxPSR: 0x01000000 pc: 0x080008fc msp: 0x20005000Loading section .isr_vector, size 0x40 lma 0x8000000Loading section .text, size 0x2a08 lma 0x8000040Start address 0x80008fc, load size 10824Transfer rate: 14 KB/sec, 5412 bytes/write.(gdb) continueContinuing.

As the result, you would see the output from the serial reciever like this:

Executing task1!task1: fib(0)=1task1: fib(1)=1task1: fib(2)=2Executing task2!task2: is_prime(1)=truetask2: is_prime(2)=truetask2: is_prime(3)=trueExecuting task1!task1: fib(3)=3task1: fib(4)=5task1: fib(5)=8Executing task2!task2: is_prime(4)=falsetask2: is_prime(5)=truetask2: is_prime(6)=false...

• mini-arm-os (https://github.com/jserv/mini-arm-os)
• tock os (https://github.com/tock/tock)