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CC3235SF LaunchXL

Overview

The SimpleLink Wi-Fi CC3235SF LaunchPad development kit (CC3235SF-LAUNCHXL) highlights CC3235SF, a single-chip wireless microcontroller (MCU) with 1MB internal flash, 4MB external serial flash, 256KB of RAM, and enhanced security features. It supports 802.11 a/b/g/n, both 2.4 GHz and 5 GHz.

See the TI CC3235 Product Page [1] for details.

Features:

Two separate execution environments: a user application dedicated ARM Cortex-M4 MCU and a network processor MCU to run all Wi-Fi and internet logical layers
40-pin LaunchPad standard leveraging the BoosterPack ecosystem
On-board accelerometer and temperature sensor
Two buttons and a RGB LED for user interaction
UART through USB to PC
BoosterPack plug-in module for adding graphical displays, audio codecs, antenna selection, environmental sensing, and more
Power from USB for the LaunchPad and optional external BoosterPack
XDS110-based JTAG emulation with serial port for flash programming

Details on the CC3235SF LaunchXL development board can be found in the CC3235SF LaunchPad Dev Kit Hardware User’s Guide [6].

Hardware

The CC3235SF SoC has two MCUs:

Applications MCU - an ARM® Cortex®-M4 Core at 80 MHz, with 256Kb RAM, and access to external serial 4MB flash with bootloader and peripheral drivers in ROM.
Network Coprocessor (NWP) - a dedicated ARM MCU, which completely offloads Wi-Fi and internet protocols from the application MCU.

Complete details of the CC3235SF SoC can be found in the CC3235 TRM [2].

Supported Features

Zephyr has been ported to the Applications MCU, with basic peripheral driver support.

Interface	Controller	Driver/Component
UART	on-chip	serial port-interrupt
GPIO	on-chip	gpio
I2C	on-chip	i2c
SPI_0	on-chip	Wi-Fi host driver

Note

For consistency with TI SimpleLink SDK and BoosterPack examples, the I2C driver defaults to I2C_BITRATE_FAST mode (400 kHz) bus speed on bootup.

The accelerometer, temperature sensors, or other peripherals accessible through the BoosterPack, are not currently supported.

Programming and Debugging

TI officially supports development on the CC3235SF using the TI CC32xx SDK [5] on Windows and Linux using TI tools: Code Composer Studio for debugging and UniFlash [4] for flashing.

For Windows developers, see the CC32xx Quick Start Guide [3] for instructions on installation of tools, and how to flash the board using UniFlash.

Note that zephyr.bin produced by the Zephyr SDK may not load via UniFlash tool. If encountering difficulties, use the zephyr.elf file and openocd instead (see below).

The following instructions are geared towards Linux developers who prefer command line tools to an IDE.

Before flashing and debugging the board, there are a few one-time board setup steps to follow.

Prerequisites:

Download and install the latest version of UniFlash [4].
Jumper SOP[2..0] (J15) to [010], and connect the USB cable to the PC.

This should result in a new device “Texas Instruments XDS110 Embed with CMSIS-DAP” appearing at /dev/ttyACM1 and /dev/ttyACM0.
Update the service pack, and place the board in “Development Mode”.

Setting “Development Mode” enables the JTAG interface, necessary for subsequent use of OpenOCD and updating XDS110 firmware.

Follow the instructions in Section 2.4 “Download the Application”, in the CC32xx Quick Start Guide [3], except for steps 5 and 6 in Section 2.4.1 which select an MCU image.
Ensure the XDS-110 emulation firmware is updated.

Download and install the latest XDS-110 emulation package [7].

Follow these xds110 firmware update directions

Note that the emulation package install may place the xdsdfu utility in <install_dir>/ccs_base/common/uscif/xds110/.
Switch Jumper SOP[2..0] (J15) back to [001].

Remove power from the board (disconnect USB cable) before switching jumpers.
Install OpenOCD

You can obtain OpenOCD by following these installing the latest Zephyr SDK instructions.

After the installation, add the directory containing the OpenOCD executable to your environment’s PATH variable. For example, use this command in Linux:
```
export PATH=$ZEPHYR_SDK_INSTALL_DIR/sysroots/x86_64-pokysdk-linux/usr/bin/openocd:$PATH
```
If you had previously installed TI OpenOCD, you can simply switch to use the one in the Zephyr SDK. If for some reason you wish to continue to use your TI OpenOCD installation, you can set the OPENOCD and OPENOCD_DEFAULT_PATH variables in boards/ti/cc3220sf_launchxl/board.cmake to point the build to the paths of the OpenOCD binary and its scripts, before including the common openocd.board.cmake file:
```
set(OPENOCD "/usr/local/bin/openocd" CACHE FILEPATH "" FORCE)
set(OPENOCD_DEFAULT_PATH /usr/local/share/openocd/scripts)
include(${ZEPHYR_BASE}/boards/common/openocd.board.cmake)
```
Ensure CONFIG_XIP=y (default) is set.

This locates the program into flash, and sets CONFIG_CC3235SF_DEBUG=y, which prepends a debug header enabling the flash to persist over subsequent reboots, bypassing the bootloader flash signature verification.

See Section 21.10 “Debugging Flash User Application Using JTAG” of the CC3235 TRM [2] for details on the secure flash boot process.

Once the above prerequisites are met, applications for the _cc3235sf_launchxl board can be built, flashed, and debugged with openocd and gdb per the Zephyr Application Development Primer (see Building an Application and Run an Application).

Flashing

To build and flash an application, execute the following commands for <my_app>:

west build -b cc3235sf_launchxl <my_app>
west flash

This will load the image into flash.

To see program output from UART0, connect a separate terminal window:

% screen /dev/ttyACM0 115200 8N1

Then press the reset button (SW1) on the board to run the program.

When using OpenOCD from Zephyr SDK to flash the device, you may notice the program hangs when starting the network processor on the device, if the program uses it. There is a known issue with how that version of OpenOCD resets the network processor. You would need to manually hit the reset button on the board to properly reset the device after flashing.

Debugging

To debug a previously flashed image, after resetting the board, use the ‘debug’ build target:

west build -b cc3235sf_launchxl <my_app>
west debug

Wi-Fi Support

The SimpleLink Host Driver, imported from the SimpleLink SDK, has been ported to Zephyr, and communicates over a dedicated SPI to the network co-processor. It is available as a Zephyr Wi-Fi device driver in drivers/wifi/simplelink.

Usage:

Set CONFIG_WIFI_SIMPLELINK and CONFIG_WIFI to y to enable Wi-Fi. See samples/net/wifi/shell/boards/cc3235sf_launchxl.conf.

Provisioning:

SimpleLink provides a few rather sophisticated Wi-Fi provisioning methods. To keep it simple for Zephyr development and demos, the SimpleLink “Fast Connect” policy is enabled, with one-shot scanning. This enables the cc3235sf_launchxl to automatically reconnect to the last good known access point (AP), without having to restart a scan, and re-specify the SSID and password.

To connect to an AP, first run the Zephyr Wi-Fi shell sample application, and connect to a known AP with SSID and password.

See Wi-Fi shell

Once the connection succeeds, the network co-processor keeps the AP identity in its persistent memory. Newly loaded Wi-Fi applications then need not explicitly execute any Wi-Fi scan or connect operations, until the need to change to a new AP.

Secure Socket Offload

The SimpleLink Wi-Fi driver provides socket operations to the Zephyr socket offload point, enabling Zephyr BSD socket API calls to be directed to the SimpleLink Wi-Fi driver, by setting CONFIG_NET_SOCKETS_OFFLOAD to y.

Secure socket (TLS) communication is handled as part of the socket APIs, and enabled by:

setting both CONFIG_NET_SOCKETS_SOCKOPT_TLS and CONFIG_TLS_CREDENTIAL_FILENAMES to y,
using the TI Uniflash tool to program the required certificates and keys to the secure flash filesystem, and enabling the TI Trusted Root-Certificate Catalog.

See HTTP GET using plain sockets and samples/net/sockets/http_get/boards/cc3235sf_launchxl.conf for an example.

See the document Simplelink Wi-Fi Certificates Handling [8] for details on using the TI UniFlash tool for certificate programming.