Overview

This is the Linux BSP (Board Support Package) for the Emcraft Systems STM32F4 System-On-Module (SOM) Starter Kit.

The BSP provides a software development environment for evaluation and development of Linux (uClinux) on the Cortex-M4 processor core of the STM32F4 microcontroller using the Emcraft Systems STM32F4 SOM Starter Kit as a hardware platform.

Supported Features

The following list summarizes the features and capabilities of this release of the STM32F4 SOM Starter Kit BSP:

• U-Boot firmware:
  • U-Boot v2010.03;
  • Target initialization from power-on / reset;
  • Runs from the internal eNVM and internal SRAM (no external memory required for standalone operation);
  • Serial console;
  • Ethernet driver for loading images to the target;
  • Serial driver for loading images to the target;
  • Device driver for built-in Flash (eNVM) and self-upgrade capability;
  • Device driver for storing environment and Linux images in external Flash;
  • Autoboot feature, allowing boot of OS images from Flash or other storage with no operator intervention;
  • Persistent environment in Flash for customization of target operation;
  • Sophisticated command interface for maintenance and development of the target.
• Linux:
  • uClinux kernel v2.6.33;
  • Ability to run critical kernel code from integrated Flash of STM32F4;
  • Serial device driver and Linux console;
  • Ethernet device driver and networking (ping, NFS, Telnet, FTP, NTPD, etc.);
  • busybox v1.17;
  • POSIX pthreads;
  • Process to kernel and process to process protection using the Memory Protection Unit (MPU) of the STM32F4 core;
  • Hardened exception handling; an exception triggered by a process affects only the offending process;
  • Loadable kernel modules;
  • Support for the hardware FPU;
  • Secure shell (ssh) daemon;
  • Web server;
  • MTD-based Flash partitioning and persistent JFFS2 Flash file system for external Flash;
  • Device driver for the DMA interface;
  • USB Host device driver;
  • I2C device driver;
  • SPI controller master-mode device driver;
  • GPIO device driver.
• Development tools:
  • ARMv7-optimized GNU toolchain from CodeSourcery (2010q1) is used for development of U-Boot, Linux and user-space applications (toolchain must be downloaded separately from the CodeSourcery web site);
  • Cross GDB for debugging user-space applications;
  • mkimage tool used by the Linux kernel build process to create a Linux image bootable by U-Boot.
• Development environment:
  • Linux-hosted cross-development environment;
  • Development of multiple projects (embedded applications) from a single installation;
  • hello sample project ("Hello, world!" single-process configuration);
  • networking sample project (basic shell, networking, USB, and Flash management tools demonstration);
  • developer sample project (template project that can be used to jump-start development of custom user-space applications and loadable kernel modules).

New and Changed Features

This section lists new and changed features of this release:

1. Support SD Card in Linux STM32F4.
   ID: RT 107790.
2. Improve STM32 I2C driver for errors handling.
   ID: RT 108659.
3. Support hardware FPU code in pthreaded applications in uClinux on Cortex-M.
   ID: RT 110109.
4. Configure STM32F4-SOM for 180 MHz. Initial support for FDT.
   ID: RT 112561.

Known Problems & Limitations

This section lists known problems and limitations of this release:

1. CONFIG_KERNEL_IN_ENVM requires disabling CONFIG_ARM_UNWIND and CONFIG_EARLY_PRINTK.
   ID: RT 74683.
   Workaround: When enabling CONFIG_KERNEL_IN_ENVM in the kernel, disable CONFIG_ARM_UNWIND and CONFIG_EARLY_PRINTK.
2. JTAG debugging rates are limited to 1 KHz.
   ID: RT 101140.
   Workaround: If you require running JTAG at higher frequencies, interrupt the Linux autoboot sequence by resetting the target and pressing any key on the serial console, thus entering the U-Boot command line interface. The Linux kernel is configured to enter a low-power mode by executing a wfi instructions whenever the system enters the so called idle loop (there are no active tasks to execute), which interferes with running JTAG at high-rate frequencies.