The OpenMote-CC2538 is based on TI's CC2538 SoC (System on Chip), featuring an ARM Cortex-M3 running at 16/32 MHz and with 32 kbytes of RAM and 512 kbytes of FLASH. It has the following key features:
* Standard Cortex M3 peripherals (NVIC, SCB, SysTick)
* Sleep Timer (underpins rtimers)
* SysTick (underpins the platform clock and Contiki's timers infrastructure)
* RF (2.4 GHz)
* UART
* Watchdog (in watchdog mode)
* USB (in CDC-ACM)
* uDMA Controller (RAM to/from USB and RAM to/from RF)
To start using Contiki with the OpenMote-CC2538, the following is required:
* An OpenMote-CC2538 board.
* A toolchain to compile Contiki for the CC2538.
* Drivers so that your OS can communicate with your hardware.
* Software to upload images to the CC2538.
Install a Toolchain
-------------------
The toolchain used to build contiki is arm-gcc, also used by other arm-based Contiki ports. If you are using Instant Contiki, you may have a version pre-installed in your system.
The platform is currently being used/tested with "GNU Tools for ARM Embedded Processors" (<https://launchpad.net/gcc-arm-embedded>). The current recommended version and the one being used by Contiki's regression tests on Travis is shown below.
$ arm-none-eabi-gcc --version
arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 5.2.1 20151202 (release) [ARM/embedded-5-branch revision 231848]
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Software to Program the Nodes
-----------------------------
The OpenMote-CC2538 can be programmed via the jtag interface or via the serial boot loader on the chip.
The OpenMote-CC2538 has a mini JTAG 10-pin male header, compatible with the `SmartRF06` development board, which can be used to flash and debug the platforms. Alternatively one could use the `JLink` programmer with a 20-to-10 pin converter like the following: <https://www.olimex.com/Products/ARM/JTAG/ARM-JTAG-20-10/>.
The serial boot loader on the chip is exposed to the user via the USB interface. To activate the bootloader short the ON/SLEEP pin to GND and then press the reset button.
Instructions to flash for different OS are given below.
* On Windows:
* Nodes can be programmed with TI's ArmProgConsole or the SmartRF Flash Programmer 2. The README should be self-explanatory. With ArmProgConsole, upload the file with a `.bin` extension.
* Nodes can also be programmed via the serial boot loader in the cc2538. In `tools/cc2538-bsl/` you can find `cc2538-bsl.py` python script, which can download firmware to your node via a serial connection. If you use this option you just need to make sure you have a working version of python installed. You can read the README in the same directory for more info.
* On Linux:
* Nodes can be programmed with TI's [UniFlash] tool. With UniFlash, use the file with `.elf` extension.
* Nodes can also be programmed via the serial boot loader in the cc2538. No extra software needs to be installed.
* On OSX:
* The `cc2538-bsl.py` script in `tools/cc2538-bsl/` is the only option. No extra software needs to be installed.
Use the Port
============
The following examples are intended to work off-the-shelf:
It is recommended to start with the `openmote-demo`, it is a simple example that demonstrates the OpenMote-CC2538 features, such as the built-in sensors, LEDs, user button and radio (using RIME broadcast).
The `Makefile.target` includes the `TARGET=` argument, predefining which is the target platform to compile for, it is automatically included at compilation.
To generate or override an existing one, you can run:
`make TARGET=openmote-cc2538 savetarget`
Then you can just run `make` to compile an application, otherwise you will need to do `make TARGET=openmote-cc2538`.
If you want to upload the compiled firmware to a node via the serial boot loader you need first to either manually enable the boot loader.
Then use `make openmote-demo.upload`.
The `PORT` argument could be used to specify in which port the device is connected, in case we have multiple devices connected at the same time.
To generate an assembly listing of the compiled firmware, run `make openmote-demo.lst`. This may be useful for debugging or optimizing your application code. To intersperse the C source code within the assembly listing, you must instruct the compiler to include debugging information by adding `CFLAGS += -g` to the project Makefile and rebuild by running `make clean openmote-demo.lst`.
To enable printing debug output to your console, use the `make login` to get the information over the USB programming/debugging port, or alternatively use `make serialview` to also add a timestamp in each print.
Node IEEE/RIME/IPv6 Addresses
-----------------------------
Nodes will generally autoconfigure their IPv6 address based on their IEEE address. The IEEE address can be read directly from the CC2538 Info Page, or it can be hard-coded. Additionally, the user may specify a 2-byte value at build time, which will be used as the IEEE address' 2 LSBs.
To configure the IEEE address source location (Info Page or hard-coded), use the `IEEE_ADDR_CONF_HARDCODED` define in contiki-conf.h:
* 0: Info Page
* 1: Hard-coded
If `IEEE_ADDR_CONF_HARDCODED` is defined as 1, the IEEE address will take its value from the `IEEE_ADDR_CONF_ADDRESS` define. If `IEEE_ADDR_CONF_HARDCODED` is defined as 0, the IEEE address can come from either the primary or secondary location in the Info Page. To use the secondary address, define `IEEE_ADDR_CONF_USE_SECONDARY_LOCATION` as 1.
Additionally, you can override the IEEE's 2 LSBs, by using the `NODEID` make variable. The value of `NODEID` will become the value of the `IEEE_ADDR_NODE_ID` pre-processor define. If `NODEID` is not defined, `IEEE_ADDR_NODE_ID` will not get defined either. For example:
make NODEID=0x79ab
This will result in the 2 last bytes of the IEEE address getting set to 0x79 0xAB
Note: Some early production devices do not have am IEEE address written on the Info Page. For those devices, using value 0 above will result in a Rime address of all 0xFFs. If your device is in this category, define `IEEE_ADDR_CONF_HARDCODED` to 1 and specify `NODEID` to differentiate between devices.
Low-Power Modes
---------------
The CC2538 port supports power modes for low energy consumption. The SoC will enter a low power mode as part of the main loop when there are no more events to service.
LPM support can be disabled in its entirety by setting `LPM_CONF_ENABLE` to 0 in `contiki-conf.h` or `project-conf.h`.
The Low-Power module uses a simple heuristic to determine the best power mode, depending on anticipated Deep Sleep duration and the state of various peripherals.
In a nutshell, the algorithm first answers the following questions:
* Is the RF off?
* Are all registered peripherals permitting PM1+?
* Is the Sleep Timer scheduled to fire an interrupt?
If the answer to any of the above question is "No", the SoC will enter PM0. If the answer to all questions is "Yes", the SoC will enter one of PMs 0/1/2 depending on the expected Deep Sleep duration and subject to user configuration and application requirements.
At runtime, the application may enable/disable some Power Modes by making calls to `lpm_set_max_pm()`. For example, to avoid PM2 an application could call `lpm_set_max_pm(1)`. Subsequently, to re-enable PM2 the application would call `lpm_set_max_pm(2)`.
The LPM module can be configured with a hard maximum permitted power mode.
#define LPM_CONF_MAX_PM N
Where N corresponds to the PM number. Supported values are 0, 1, 2. PM3 is not supported. Thus, if the value of the define is 1, the SoC will only ever enter PMs 0 or 1 but never 2 and so on.
The configuration directive `LPM_CONF_MAX_PM` sets a hard upper boundary. For instance, if `LPM_CONF_MAX_PM` is defined as 1, calls to `lpm_set_max_pm()` can only enable/disable PM1. In this scenario, PM2 can not be enabled at runtime.
When setting `LPM_CONF_MAX_PM` to 0 or 1, the entire SRAM will be available. Crucially, when value 2 is used the linker will automatically stop using the SoC's SRAM non-retention area, resulting in a total available RAM of 16 kbytes instead of 32 kbytes.
### LPM and Duty Cycling Driver
LPM is highly related to the operations of the Radio Duty Cycling (RDC) driver of the Contiki network stack and will work correctly with ContikiMAC and NullRDC.
* With ContikiMAC, PMs 0/1/2 are supported subject to user configuration.
* When NullRDC is in use, the radio will be always on. As a result, the algorithm discussed above will always choose PM0 and will never attempt to drop to PM1/2.
Build headless nodes
--------------------
It is possible to turn off all character I/O for nodes not connected to a PC. Doing this will entirely disable the UART as well as the USB controller, preserving energy in the long term. The define used to achieve this is (1: Quiet, 0: Normal output):
#define CC2538_CONF_QUIET 0
Setting this define to 1 will automatically set the following to 0:
*`USB_SERIAL_CONF_ENABLE`
*`UART_CONF_ENABLE`
*`STARTUP_CONF_VERBOSE`
Code Size Optimisations
-----------------------
The build system currently uses optimization level `-Os`, which is controlled indirectly through the value of the `SMALL` make variable. This value can be overridden by example makefiles, or it can be changed directly in `platform/openmote-cc2538/Makefile.openmote-cc2538`.
Historically, the `-Os` flag has caused problems with some toolchains. If you are using one of the toolchains documented in this README, you should be able to use it without issues. If for whatever reason you do come across problems, try setting `SMALL=0` or replacing `-Os` with `-O2` in `cpu/cc2538/Makefile.cc2538`.
Doxygen Documentation
=====================
This port's code has been documented with doxygen. To build the documentation, navigate to `$(CONTIKI)/doc` and run `make`. This will build the entire contiki documentation and may take a while.
If you want to build this platform's documentation only and skip the remaining platforms, run this:
make basedirs="platform/openmote-cc2538 core cpu/cc2538 examples/openmote-cc2538 examples/openmote-cc2538"
Once you've built the docs, open `$(CONTIKI)/doc/html/index.html` and enjoy.
Other Versions of this Guide
============================
If you prefer this guide in other formats, use the excellent [pandoc] to convert it.
