osd-contiki/platform/srf06-cc26xx

Getting Started with Contiki for TI CC26xx

This guide's aim is to help you start using Contiki for TI's CC26xx. The platform supports two different boards:

• SmartRF 06 Evaluation Board with a CC26xx or CC13xx Evaluation Module (relevant files and drivers are under srf06/)
• CC2650 SensorTag 2.0 (relevant drivers under sensortag/cc2650)

The CPU code, common for both platforms, can be found under $(CONTIKI)/cpu/cc26xx-cc13xx. The port was developed and tested with CC2650s, but the intention is for it to work with the CC2630 as well. Thus, bug reports are welcome for both chips. Bear in mind that the CC2630 does not have BLE capability.

This port is only meant to work with 7x7mm chips

This guide assumes that you have basic understanding of how to use the command line and perform basic admin tasks on UNIX family OSs.

Port Features

The platform has the following key features:

• Deep Sleep support with RAM retention for ultra-low energy consumption.
• Support for CC26xx RF in IEEE as well as BLE mode (BLE support is very basic since Contiki does not provide a BLE stack).
• Support for CC13xx prop mode: IEEE 802.15.4g-compliant sub GHz operation

In terms of hardware support, the following drivers have been implemented:

• SmartRF06 EB peripherals
  • LEDs
  • Buttons
  • UART connectivity over the XDS100v3 backchannel
• SensorTag 2.0
  • LEDs
  • Buttons (One of the buttons can be used as a shutdown button)
  • Reed relay
  • Motion Processing Unit (MPU9250 - Accelerometer, Gyro)
  • BMP280 sensor
  • TMP007 sensor
  • HDC1000 sensor
  • OPT3001 sensor
  • Buzzer
  • External SPI flash

Requirements

To use the port you need:

• TI's CC26xxware sources. The correct version will be installed automatically as a submodule when you clone Contiki.

• TI's CC13xxware sources. The correct version will be installed automatically as a submodule when you clone Contiki.

• Contiki can automatically upload firmware to the nodes over serial with the included cc2538-bsl script. Note that uploading over serial doesn't work for the Sensortag, you can use TI's SmartRF Flash Programmer in this case.

• A toolchain to build firmware: The port has been developed and 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.
  

• srecord (http://srecord.sourceforge.net/)

• You may also need other drivers so that the SmartRF can communicate with your operating system and so that you can use the chip's UART for I/O. Please read the section "Drivers" in the CC2538DK readme.

Examples

The port comes with three examples:

• A very basic example which demonstrates how to read sensors and how to use board peripherals. It also demonstrates how to send out BLE advertisements.
• A more advanced one (web demo) which includes a CoAP server, an MQTT client which connects and publishes to the IBM quickstart service, a net-based UART and lastly a web server that can be used to configure the rest of the example.
• An example demonstrating a very sleepy node.

More details about those three examples can be found in their respective READMEs.

Build your First Example

It is recommended to start with the cc26xx-demo example under examples/cc26xx/. This is a very simple example which will help you get familiar with the hardware and the environment. This example can be used for the Sensortag and SmartRF06 EB.

Strictly speaking, to build it you need to run make TARGET=srf06-cc26xx BOARD=srf06/cc26xx. However, the example directories contain a Makefile.target which is automatically included and specifies the correct TARGET= argument. The BOARD= environment variable defaults to srf06/cc26xx (which is the SmartRF06 EB + CC26XXEM). Thus, for examples under the cc26xx directory, and when using the SmartRF06 EB, you can simply run make.

Other options for the BOARD make variable are:

• Srf06+CC26xxEM: Set BOARD=srf06/cc26xx
• Srf06+CC13xxEM: Set BOARD=srf06/cc13xx
• CC2650 tag: Set BOARD=sensortag/cc2650

If the BOARD variable is unspecified, an image for the Srf06 CC26XXEM will be built.

If you want to switch between building for one platform to the other, make certain to make clean before building for the new one, or you will get linker errors.

If you want to upload the compiled firmware to a node via the serial boot loader you need to manually enable the boot loader and then use make cc26xx-demo.upload. On the SmartRF06 board you enable the boot loader by resetting the board (EM RESET button) while holding the select button. (The boot loader backdoor needs to be enabled on the chip, and the chip needs to be configured correctly, for this to work. See README in the tools/cc2538-bsl directory for more info). The serial uploader script will automatically pick the first available serial port. If this is not the port where your node is connected, you can force the script to use a specific port by defining the PORT argument eg. make cc26xx-demo.upload PORT=/dev/tty.usbserial

Note that uploading over serial doesn't work for the Sensortag, you can use TI's SmartRF Flash Programmer in this case.

For the cc26xx-demo, the included readme describes in detail what the example does.

To generate an assembly listing of the compiled firmware, run make cc26xx-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 cc26xx-demo.lst.

CC13xx/CC26xx Border Router over UART

The platform code can be used as a border router (SLIP over UART) by using the example under examples/ipv6/rpl-border-router. This example defines the following:

#ifndef UIP_CONF_BUFFER_SIZE
#define UIP_CONF_BUFFER_SIZE    140
#endif

#ifndef UIP_CONF_RECEIVE_WINDOW
#define UIP_CONF_RECEIVE_WINDOW  60
#endif

The CC26xx port has much higher capability than some other platforms used as border routers. Thus, before building the example, it is recommended to delete these two configuration directives. This will allow platform defaults to take effect and this will improve performance and stability.

Do not forget to set the correct channel by defining RF_CORE_CONF_CHANNEL as required.

CC13xx/CC26xx slip-radio with 6lbr

The platform can also operate as a slip-radio over UART, to be used with 6lbr.

Similar to the border router configuration, you will need to remove the defines that limit the size of the uIP buffer. Removing the two lines below from examples/ipv6/slip-radio/project-conf.h should do it.

#undef UIP_CONF_BUFFER_SIZE
#define UIP_CONF_BUFFER_SIZE    140

Do not forget to set the correct channel by defining RF_CORE_CONF_CHANNEL as required.

Filename conflicts between Contiki and CC26xxware

There is a file called timer.c both in Contiki as well as in CC26xxware. The way things are configured now, we don't use the latter. However, if you need to start using it at some point, you will need to rename it:

From cpu/cc26xx/lib/cc26xxware/driverlib/timer.c to driverlib-timer.c

Sensortag UART usage (with or without the Debugger Devpack)

There are two ways to get debugging (printf etc) output from the Sensortag.

• Purchase a Debugger Devpack and set BOARD_CONF_DEBUGGER_DEVPACK to 1 in contiki-conf.h or project-conf.h. This will work off the shelf for revision 1.2.0 of the debugger devpack.
• If you have an older (rev 1.0.0) devpack, you will need to do the above and then to modify board.h in order to cross the RX and TX DIO mappings. (TX to IOID_28, RX to IOID_29).
• If you don't have/want a debugger devpack, you can use a SmartRF and modify the jumper configuration on P408 as discussed in this thread on E2E. For this to work, you need to set BOARD_CONF_DEBUGGER_DEVPACK to 0.

Low Power Operation

The platform takes advantage of the CC26xx's power saving features. In a nutshell, here is how things work:

• When the RF is TXing, the CPU will enter sleep mode and will resume after TX has completed.
• When there are no events in the Contiki event queue, the chip will enter 'some' low power mode (more below).

We do not use pre-defined power profiles (e.g. as mentioned in the TRM or as we do for the CC2538 with LPM1, LPM2 etc). Each time we enter low power operation, we either put the CM3 to sleep or to deep sleep. The latter case is highly configurable: the LPM engine allows other code modules to register themselves for notifications and to configure low power operation. With these facilities, a module can e.g. prohibit deep sleep altogether, or it can request that a power domain be kept powered. The LPM engine will turn off as many CC26xx components as it can while satisfying all restrictions set by registered modules.

To determine which power mode to use, the following logic is followed:

• The deepest available low power mode can be hard-coded by using the LPM_MODE_MAX_SUPPORTED macro in the LPM driver (lpm.[ch]). Thus, it is possible to prohibit deep sleep altogether.
• Code modules which are affected by low power operation can 'register' themselves with the LPM driver.
• If the projected low-power duration is lower than STANDBY_MIN_DURATION, the chip will simply sleep.
• If the projected low power duration is sufficiently long, the LPM will visit all registered modules to query the maximum allowed power mode (maximum means sleep vs deep sleep in this context). It will then drop to this power mode. This is where a code module can forbid deep sleep if required.
• All registered modules will be notified when the chip is about to enter deep sleep, as well as after wake-up.

When the chip does enter deep sleep:

• The RF Core, VIMS, SYSBUS and CPU power domains are always turned off. Due to the way the RF driver works, the RFCORE PD should be off already.
• Peripheral clocks stop
• The Serial and Peripheral power domains are turned off, unless an LPM module requests them to stay operational. For example, the net-uart demo keeps the serial power domain powered on and the UART clocked under sleep and deep sleep in order to retain UART RX functionality.
• If both SERIAL and PERIPH PDs are turned off, we also switch power source to the uLDO for ultra low leakage under deep sleep.

The chip will come out of low power mode by one of the following events:

• Button press or, in the case of the SensorTag, a reed relay trigger
• Software clock tick (timer). The clock ticks at 128Hz, therefore the maximum time we will ever spend in a sleep mode is 7.8125ms. In hardware terms, this is an AON RTC Channel 2 compare interrupt.
• Rtimer triggers, as part of ContikiMAC's sleep/wake-up cycles. The rtimer sits on the AON RTC channel 0.