openmote-cc2538: OpenMote cc2538

The OpenMote platform 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 256/512 kbytes of FLASH.

The OpenMote platform supports two boards:

  • The original OpenMote (openmote-cc2538)

  • The new OpenMote revision B (openmote-b). This board also features a sub-ghz radio, which is currently not supported. Support for this board was added in release 4.4 and is considered experimental.

It has the following key features:

  • Standard Cortex M3 peripherals (NVIC, SCB, SysTick)

  • Sleep Timer (underpins rtimers)

  • SysTick (underpins the platform clock and Contiki-NG’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)

  • Random number generator

  • Low Power Modes

  • General-Purpose Timers

  • ADC

  • Cryptoprocessor (AES-ECB/CBC/CTR/CBC-MAC/GCM/CCM-128/192/256, SHA-256)

  • Public Key Accelerator (ECDH, ECDSA)

  • Flash-based port of Coffee

  • PWM

  • Built-in core temperature and battery sensor


To start using Contiki-NG with the OpenMote-CC2538, the following is required:

  • An OpenMote-CC2538 board with a OpenUSB, OpenBase or OpenBattery carrier boards.

  • A toolchain to compile Contiki-NG for the CC2538.

  • Drivers so that your OS can communicate with your hardware.

  • Software to upload images to the CC2538.

Toolchain Installation

The toolchain used to build Contiki-NG is arm-gcc, also used by other arm-based Contiki-NG ports.

If you use the docker image or the vagrant image, this will be pre-installed for you. Otherwise, depending on your system, please follow the respective installation instructions (native Linux / native mac OS).

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:

The serial boot loader on the chip is exposed to the user via the USB interface of both the OpenUSB and the OpenBase carrier boards. The OpenUSB carrier board is capable to automatically detect the boot loader sequence and flash the CC2538 without user intervention. The OpenBase carrier board does not have such feature, so to activate the bootloader the user needs to 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 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 script in tools/cc2538-bsl/ is the only option. No extra software needs to be installed.

Build your First Examples

One can start with the platform-independent examples/hello-world. For a review of make targets see doc:build-system.

To build the example, run make TARGET=openmote. This will build for the default board openmote-cc2538. To switch between boards, use the BOARD variable. For example:

make TARGET=openmote BOARD=openmote-cc2538 or make TARGET=openmote BOARD=openmote-b

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 hello-world.upload.

If you are compiling for the OpenMote-CC2538 Rev.A1 board (CC2538SF53, 256 KB Flash) you have to pass BOARD_REVISION=REV_A1 in all your make commands to ensure that the linking stage configures the linker script with the appropriate parameters. If you are compiling for older OpenMote-CC2538 revisions (CC2538SF53, 512 KB Flash) you can skip this parameter since the default values are already correct.

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 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 and 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. 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.

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:




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.


The original OpenMote-CC2538 was developed by OpenMote Technologies. Main contributor: Pere Tuset

Suipport for OpenMote B was developed by Anders Wallberg (@wallb)