硬件

现在你应该熟悉了工具与开发过程. 在本节我们来试试真正的硬件. 该过程基本不变.让我们开始:

了解你的硬件

在我们开始之前你需要了解硬件的特点以便于配置项目:

ARM内核. e.g. Cortex-M3.
ARM内核有FPU吗? Cortex-M4F和Cortex-M7F有.
目标设备有多大闪存和RAM? e.g. 256KiB闪存32KiB内存.
闪存和RAM在的地址在多少? e.g. RAM通常位于0x2000_0000.

你可以在用户手册和数据手册中找到这些信息.

在本届我们使用我们的参考硬件STM32F3DISCOVERY. 这块板子有一个STM32F303VCT6.这块MCU有:

一个带有单精度FPU的Cortex-M4F内核
位于0x0800_0000的256KiB闪存
位于0x2000_0000的40KiB内存(还有另一个RAM区域,为了简单我们忽略)

配置

我们从一个新的模板实例开始. 关于如何使用cargo-generate请参考上一章节QEMU

$ cargo generate --git https://github.com/rust-embedded/cortex-m-quickstart
 Project Name: app
 Creating project called `app`...
 Done! New project created /tmp/app

$ cd app

第一步是在.cargo/config中设置默认编译目标.

$ tail -n5 .cargo/config

# Pick ONE of these compilation targets
# target = "thumbv6m-none-eabi"    # Cortex-M0 and Cortex-M0+
# target = "thumbv7m-none-eabi"    # Cortex-M3
# target = "thumbv7em-none-eabi"   # Cortex-M4 and Cortex-M7 (no FPU)
target = "thumbv7em-none-eabihf" # Cortex-M4F and Cortex-M7F (with FPU)

我们使用thumbv7em-none-eabihf,因为它包含Cortex-M4F内核.

第二步是把内存区域信息输入到memory.x中.

$ cat memory.x
/* Linker script for the STM32F303VCT6 */
MEMORY
{
  /* NOTE 1 K = 1 KiBi = 1024 bytes */
  FLASH : ORIGIN = 0x08000000, LENGTH = 256K
  RAM : ORIGIN = 0x20000000, LENGTH = 40K
}

NOTE如果你因为某些原因修改了memory.x,并且之前做过了编译, 那你需要执行cargo clean再执行cargo build,因为cargo build并不会追踪memory.x的变化.

我们还用hello这个例子, 但是首先先做一点小改动.

在examples/hello.rs中,确保debug::exit()被注释掉或者删掉.它只是为了运行QEMU而存在的.

#[entry]
fn main() -> ! {
    hprintln!("Hello, world!").unwrap();

    // exit QEMU
    // NOTE do not run this on hardware; it can corrupt OpenOCD state
    // debug::exit(debug::EXIT_SUCCESS);

    loop {}
}

现在你可以用cargo build进行交叉编译,并且像之前一样用cargo-binutils查看信息. cortex-m-rt这个库包含了一切能让你芯片运行的魔法,它很有帮助,因为几乎所有的Cortex-M CPU都可以用相同的方式引导.

$ cargo build --example hello

调试

调试过程看起来有些不同了.事实上,第一步根据目标设备不同也有不同.这一节中我们会展示在STM32DISCOBVERY上debug的步骤.这仅供参考,有关设备的调试请参考the Debugonomicon.

和以前一样,我们进行远程调试,客户端是GDB.但是这次服务端则是OpenOCD.

像之前在验证安装中所做的一样,将板子连接到电脑,然后检查ST-LINK.

在终端上运行OpenOCD以连接到ST-LINK.从模板的根目录运行此命令;OpenOCD会使用openocd.cfg,这里面声明了使用什么接口,连接什么设备.

$ cat openocd.cfg

# Sample OpenOCD configuration for the STM32F3DISCOVERY development board

# Depending on the hardware revision you got you'll have to pick ONE of these
# interfaces. At any time only one interface should be commented out.

# Revision C (newer revision)
source [find interface/stlink.cfg]

# Revision A and B (older revisions)
# source [find interface/stlink-v2.cfg]

source [find target/stm32f3x.cfg]

NOTE 如果你在用旧版本的DISCOVERY板子,你应该修改一下openocd.cfg来使用interface/stlink-v2.cfg

$ openocd
Open On-Chip Debugger 0.10.0
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : auto-selecting first available session transport "hla_swd". To override use 'transport select <transport>'.
adapter speed: 1000 kHz
adapter_nsrst_delay: 100
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
none separate
Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : clock speed 950 kHz
Info : STLINK v2 JTAG v27 API v2 SWIM v15 VID 0x0483 PID 0x374B
Info : using stlink api v2
Info : Target voltage: 2.913879
Info : stm32f3x.cpu: hardware has 6 breakpoints, 4 watchpoints

同样在根目录下另起一个终端运行GDB.

$ <gdb> -q target/thumbv7em-none-eabihf/debug/examples/hello

先一步连接GDB到OpenOCD.

(gdb) target remote :3333
Remote debugging using :3333
0x00000000 in ?? ()

现在使用load命令烧录程序到mcu.

(gdb) load
Loading section .vector_table, size 0x400 lma 0x8000000
Loading section .text, size 0x1e70 lma 0x8000400
Loading section .rodata, size 0x61c lma 0x8002270
Start address 0x800144e, load size 10380
Transfer rate: 17 KB/sec, 3460 bytes/write.

现在程序被加载了.之前程序使用semihosting,因此在我们进行任何semihosting操作时,应该先告诉OpenOCD启用semihosting.可以使用monitor命令.

(gdb) monitor arm semihosting enable
semihosting is enabled

你也可以使用monitor help查看所用OpenOCD命令.

前之前那样给main加断点并执行continue

(gdb) break main
Breakpoint 1 at 0x8000d18: file examples/hello.rs, line 15.

(gdb) continue
Continuing.
Note: automatically using hardware breakpoints for read-only addresses.

Breakpoint 1, main () at examples/hello.rs:15
15          let mut stdout = hio::hstdout().unwrap();

NOTE 如果在发出上面的continue命令后GDB阻塞了终端而不是到达断点，则你可能要仔细检查一下是否已为您的设备正确设置了memory.x文件中的存储区域信息(起始位置和长度).

使用next继续程序,应该会有和之前相同的结果.

(gdb) next
16          writeln!(stdout, "Hello, world!").unwrap();

(gdb) next
19          debug::exit(debug::EXIT_SUCCESS);

在这我们应该看到在OpenOCD的控制台上出现了"Hello, world!"

$ openocd
(..)
Info : halted: PC: 0x08000e6c
Hello, world!
Info : halted: PC: 0x08000d62
Info : halted: PC: 0x08000d64
Info : halted: PC: 0x08000d66
Info : halted: PC: 0x08000d6a
Info : halted: PC: 0x08000a0c
Info : halted: PC: 0x08000d70
Info : halted: PC: 0x08000d72

发出另一个next命令会使程序执行debug::exit().这会触发断点并终止程序:

(gdb) next

Program received signal SIGTRAP, Trace/breakpoint trap.
0x0800141a in __syscall ()

这也会使以下内容出现在OpenOCD控制台上:

$ openocd
(..)
Info : halted: PC: 0x08001188
semihosting: *** application exited ***
Warn : target not halted
Warn : target not halted
target halted due to breakpoint, current mode: Thread
xPSR: 0x21000000 pc: 0x08000d76 msp: 0x20009fc0, semihosting

但是,mcu上的进程不没有终止,你可以使用continue或类似的命令恢复进程.

你现在可以用quit来退出GDB

(gdb) quit

现在调试需要更多的步骤了,那让我们来把这些步骤打包成一个叫openocd.gdb的GDB脚本. 这个文件在cargo generate步骤中已经生成了,按理说不用做修改就能用.让我们看一下:

$ cat openocd.gdb

target extended-remote :3333

# print demangled symbols
set print asm-demangle on

# detect unhandled exceptions, hard faults and panics
break DefaultHandler
break HardFault
break rust_begin_unwind

monitor arm semihosting enable

load

# start the process but immediately halt the processor
stepi

现在运行<gdb> -x openocd.gdb target/thumbv7em-none-eabihf/debug/examples/hello会自动连接GDB到OpenOCD,启动semihosting,然后烧录程序并启动.

$ head -n10 .cargo/config

[target.thumbv7m-none-eabi]
# uncomment this to make `cargo run` execute programs on QEMU
# runner = "qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -nographic -semihosting-config enable=on,target=native -kernel"

[target.'cfg(all(target_arch = "arm", target_os = "none"))']
# uncomment ONE of these three option to make `cargo run` start a GDB session
# which option to pick depends on your system
runner = "arm-none-eabi-gdb -x openocd.gdb"
# runner = "gdb-multiarch -x openocd.gdb"
# runner = "gdb -x openocd.gdb"

$ cargo run --example hello
(..)
Loading section .vector_table, size 0x400 lma 0x8000000
Loading section .text, size 0x1e70 lma 0x8000400
Loading section .rodata, size 0x61c lma 0x8002270
Start address 0x800144e, load size 10380
Transfer rate: 17 KB/sec, 3460 bytes/write.
(gdb)

嵌入式Rust之书

硬件

了解你的硬件

配置

调试