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Diffstat (limited to 'user/bsps/arm/beagle.rst')
| -rw-r--r-- | user/bsps/arm/beagle.rst | 176 |
1 files changed, 161 insertions, 15 deletions
diff --git a/user/bsps/arm/beagle.rst b/user/bsps/arm/beagle.rst index fe2dc6f..55f75c0 100644 --- a/user/bsps/arm/beagle.rst +++ b/user/bsps/arm/beagle.rst @@ -2,6 +2,12 @@ .. Copyright (C) 2019 Vijay Kumar Banerjee +.. _BSP_arm_beagle: +.. _BSP_arm_beagleboardorig: +.. _BSP_arm_beagleboardxm: +.. _BSP_arm_beagleboneblack: +.. _BSP_arm_beaglebonewhite: + beagle ====== @@ -26,7 +32,7 @@ To boot via uboot, the ELF must be converted to a U-Boot image like below: .. code-block:: none - arm-rtems5-objcopy hello.exe -O binary app.bin + arm-rtems@rtems-ver-major@-objcopy hello.exe -O binary app.bin gzip -9 app.bin mkimage -A arm -O linux -T kernel -a 0x80000000 -e 0x80000000 -n RTEMS -d app.bin.gz rtems-app.img @@ -61,23 +67,39 @@ Add the following to a file named uEnv.txt: I2C Driver ---------- -The Beagle has the `i2c-0` device registered at initialization. For registering -`i2c-1` and `i2c-2` ``bbb_register_i2c_1()`` and -``bbb_register_i2c_2()`` wrapper functions are respectively used. +The Beagle i2c initialization is based on the device tree. To initialize a i2c +device, the user has to enable the respective node in the device tree using +overlays. -For registering an I2C device with a custom path (say `/dev/i2c-3`) the -function ``am335x_i2c_bus_register()`` has to be used. +For registering an I2C device with a custom path (say `/dev/i2c-eeprom`) an +overlay has to be provided. The overlay must add an additional attribute +`rtems,path` with the custom path as value to the respective i2c node. -The function prototype is given below: +For example, + +.. code-block:: none + + /dts-v1/; + + / { + compatible = "ti,am335x-bone-black", "ti,am335x-bone", "ti,am33xx"; -.. code-block:: C + fragment@0 { + target = <0xffffffff>; - int am335x_i2c_bus_register( - const char *bus_path, - uintptr_t register_base, - uint32_t input_clock, - rtems_vector_number irq - ); + __overlay__ { + compatible = "rtems,bsp-i2c", "ti,omap4-i2c"; + status = "okay"; + rtems,path = "/dev/i2c-eeprom"; + }; + }; + + __fixups__ { + i2c0 = "/fragment@0:target:0"; + }; + }; + +The above example registers a custom path `/dev/i2c-eeprom` for i2c0. SPI Driver ---------- @@ -88,10 +110,134 @@ For registering with a custom path, the ``bsp_register_spi()`` can be used. The function prototype is given below: -.. code-block:: C +.. code-block:: c rtems_status_code bsp_register_spi( const char *bus_path, uintptr_t register_base, rtems_vector_number irq ); + +Debugging using libdebugger +--------------------------- + +RTEMS's ``libdebugger`` requires the ARM debug resources be enabled for it to +work. The TI SOC used on the ``beagleboneblack`` board provides no access for +software to the ARM defined debug enable signal ``DBGEN``. The signal is +negated on power up locking software out of the ARM debug hardware. The signal +can only be accessed via the JTAG interface. + +The ``beagleboneblack`` BSP provides a low level solution to enable the +``DBGEN`` signal via the JTAG interface if the board has the following +hardware modification installed. The modification requires the addition of two +small wire links soldered to the pads of the JTAG connect on the underside of +the board. A small length of fine wire, a fine tip soldering iron, some good +quality solder and a pair of fine tip pliers are required. If you are new to +soldering I suggest you find something to practice on first. + +The modification details and software driver can be found in the BSP in the +file ``bsps/arm/beagle/start/bspdebug.c``. The driver is automatically run +and the ``DBGEN`` is asserted via JTAG when ``libdebugger`` is started. + +The modification is: + +1. Locate P2 on the bottom side of the board. It is the JTAG connector + pads. If you look at the underside of the board with the SD card holder to + the right the pads are top center left. There are 20 pads in two + columns. The pads are numbered 1 at the top left then 2 top right, 3 is + second top on the left, 4 is second top to the right, then the pin number + increments as you move left then right down the pads. + +2. Connect P2 to P5. + +3. Connect P7 to P13. + +The resulting wiring is: + +.. code-block:: none + + 1 === /--=== 2 + 3 === | === 4 + 5 ===--/ === 6 + 7 ===--\ === 8 + 9 === | === 10 + 11 === | === 12 + 13 ===--/ === 14 + 15 === === 16 + 17 === === 18 + 19 === === 20 + +.. figure:: ../../../images/user/bbb-p2-debug-mod.jpg + :width: 50% + :align: center + :alt: BeagleBone Black JTAG Hardware Modification + + BeagleBone Black JTAG Hardware Modification + +If ``libdebugger`` fails to detect the registers open the ``bspdebug.c`` +source and change ``has_tdo`` to ``1``, save then rebuild and install the +BSP. This will turn on an internal feeback to check the JTAG logic. Discard +the edit once the hardware is working. + +Debugging Beagle Bone Black using a JTAG debugger and gdb +--------------------------------------------------------- + +Debugging a Beagle Bone Black (or variants) is also possible using a hardware +JTAG debugger. The JTAG is available via P2. The footprint is for an ARM 20 pin +cTI connector. That connector should be used, if it is necessary to have access +to commercially available adapters. + +For hand-made cables and adapters a standard 1.27mm pitch header and a 0.635mm +ribbon cable can be much cheaper. But note that even if it looks compatible, +it's not the same pin out as a ARM Cortex 20 pin connector! + +A lot of JTAG adapters that are working together with OpenOCD will work. There +are also commercially available systems (like Segger J-Link) that work well with +the Beagle. Note that the JTAG debugger has to be compatible with ARM Cortex A8. +Cortex M only debuggers (like the Segger J-Link Edu Mini) won't work. + +If the debugger offers a gdb server (like OpenOCD or Segger J-Link) the +following gdb start script can be used: + +.. code-block:: none + + define reset + echo -- Reset target and wait for U-Boot to start kernel.\n + monitor reset + # RTEMS U-Boot starts at this address. + tbreak *0x80000000 + # Linux starts here. + tbreak *0x82000000 + continue + + echo -- Disable watchdog.\n + set *(uint32_t*)0x44e35048=0xAAAA + while (*(uint32_t*)0x44e35034 != 0) + end + set *(uint32_t*)0x44e35048=0x5555 + while (*(uint32_t*)0x44e35034 != 0) + end + + echo -- Overwrite kernel with application to debug.\n + load + end + + target remote :2331 + +Note that you might have to replace the ``monitor reset`` by some other command +that resets the target using your specific debugger. You also have to replace +the ``target remote :2331`` to match the port of your gdb server. + +The script expects that the Beagle Bone Black starts some application from an SD +card or from eMMC. It defines a ``reset`` command that does the following: + + * reset the target + * let U-Boot run, initialize the base system, load an FDT and an application + * break at the application entry point + * disable the watchdog + * overwrite the application that has been loaded by U-Boot with the application + provided as an command line argument to gdb + +This method has the advantage that the application is executed in nearly the +same environment like it would be executed if loaded by U-Boot directly (except +for the watchdog). |