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Pebble Smartwatch QEMU Implementation

Overview

This is a derivative of QEMU v2.1.1 that has been modified to include an implementation of the STM32F2xx microcontroller. This is based off of a QEMU fork that is targeting the STM32F103: https://github.com/beckus/qemu_stm32. This repo contains both beckus' STM32F1xx implementation and Pebble's STM32F2xx additions.

DANGER DANGER: It is very much a work-in-progress! Only some of the peripherals are working at the moment. Please contribute!

Dependencies

QEMU requires that development packages for glib20 and pixman are installed.

FreeBSD

Install the devel/glib20 and x11/pixman ports.

Linux

Mac OS X

Windows

Building

Commands for a typical build:

git submodule update --init dtc
./configure --disable-werror --enable-debug --target-list="arm-softmmu" \
    --extra-cflags="-DSTM32_UART_NO_BAUD_DELAY -std=c99"
make

Summary set of configure options that are useful when developing (tested only on OS X 10.9.5):

    ./configure --enable-tcg-interpreter --extra-ldflags=-g \
    --with-coroutine=gthread --enable-debug-tcg --enable-cocoa \
    --enable-debug --disable-werror --target-list="arm-softmmu" \
    --extra-cflags=-DDEBUG_CLKTREE --extra-cflags=-DDEBUG_STM32_RCC \
    --extra-cflags=-DDEBUG_STM32_UART --extra-cflags=-DSTM32_UART_NO_BAUD_DELAY \
    --extra-cflags=-DDEBUG_GIC

####Configure options which control the STM32 implementation:

--extra-cflags=-DDEBUG_CLKTREE
    Print out clock tree debug statements.

--extra-cflags=-DDEBUG_STM32_RCC
    Print RCC debug statements.

--extra-cflags=-DDEBUG_STM32_UART
    Print UART debug statements.

--extra-cflags=-DSTM32_UART_NO_BAUD_DELAY
    Disable the BAUD rate timing simulation
    (i.e. the UART will transmit or receive as fast as possible, rather than
    using a realistic delay).

--extra-cflags=-DSTM32_UART_ENABLE_OVERRUN
    Enable setting of the overrun flag if a character is
    received before the last one is processed.  If this is not set, the UART
    will not receive the next character until the previous one is read by
    software.  Although less realisitic, it is safer NOT to use this, in case the VM is
    running slow.

####Other QEMU configure options which are useful for troubleshooting: --extra-cflags=-DDEBUG_GIC Extra logging around which interrupts are asserted

####qemu-system-arm options which are useful for troubleshooting: -d ? To see available log levels

-d cpu,in_asm
    Enable logging to view the CPU state during execution and the ARM
    instructions which are being executed.  I believe --enable-debug must be
    used for this to work.

Useful make commands when rebuilding:

    make defconfig
    make clean

Generating Images

  • Use ./waf build qemu_image_spi to generate qemu_spi_flash.bin from tintin.
  • Use ./waf build qemu_image_micro to generate qemu_micro_flash.bin from tintin.

Under the covers of the images

QEMU's -pflash argument is used to specify a file to use as the micro flash. An image can be created by concatenating the boot and main firmware files, like so:

truncate -s 64k tintin_boot.bin
cat tintin_boot.bin tintin_fw.bin > micro_flash.bin
truncate -s 512k micro_flash.bin

Running

There is a convenience script pebble.sh that runs QEMU. It depends on the existence of (symlinked) images qemu_micro_flash.bin and qemu_spi_flash.bin.

More details about running QEMU

The generated executable is arm-softmmu/qemu-system-arm .

Example:

    qemu-system-arm -rtc base=localtime -machine pebble-bb2 -cpu cortex-m3 -s \
    -pflash qemu_micro_flash.bin -mtdblock qemu_spi_flash.bin

Adding -S to the commandline will have QEMU wait in the monitor at start; the _c_ontinue command is necessary to start the virtual CPU.

QEMU Docs

Read original the documentation in qemu-doc.html or on http://wiki.qemu.org

QEMU Modifications

This emulator consists largely of new hardware device models; it includes only minor changes to existing QEMU functionality.

The changes can be reviewed by running git diff --diff-filter=M v1.5.0-backports.

To list the added files, use git diff --name-only --diff-filter=A v1.5.0-backports.

License

The following points clarify the QEMU license:

  1. QEMU as a whole is released under the GNU General Public License

  2. Parts of QEMU have specific licenses which are compatible with the GNU General Public License. Hence each source file contains its own licensing information.

Many hardware device emulation sources are released under the BSD license.

  1. The Tiny Code Generator (TCG) is released under the BSD license (see license headers in files).

  2. QEMU is a trademark of Fabrice Bellard.