Bluetooth® SPI-based datalogger

This code example includes two applications that demonstrate the operation of multiple serial peripheral interface (SPI) interfaces using the CYW208XX Bluetooth® SoC and ModusToolbox™ software. The first application demonstrates the operation of two SPI masters – one for collecting sensor data and the other for logging the data to external flash. The second application demonstrates the operation of an SPI slave used for providing sensor data to the first application.

Requirements

ModusToolbox™ software v2.4 or later (tested with v2.4).
Board support package (BSP) minimum required version: 3.0.0
Programming language: C
Associated parts: AIROC™ CYW20819 Bluetooth® & Bluetooth® LE system-on-chip, AIROC™ CYW20820 Bluetooth® & Bluetooth® LE system-on-chip

Supported toolchains (make variable 'TOOLCHAIN')

GNU Arm® embedded compiler v9.3.1 (GCC_ARM) - Default value of TOOLCHAIN

Supported kits (make variable 'TARGET')

CYW920820M2EVB-01 evaluation kit (CYW920820M2EVB-01) – Default value of TARGET
CYW920819M2EVB-01 evaluation kit(CYW920819M2EVB-01)
CYW920819EVB-02 evaluation kit (CYW920819EVB-02)
CYW920820EVB-02 evaluation kit (CYW920820EVB-02)

Hardware setup

These applications run on two separate kits. Both applications use the kit’s default configuration. See the kit guide, if required, to ensure that the kit is configured correctly. Figure 1 shows the block diagram depicting the connections between different blocks of two evaluation boards.

Figure 1. Block diagram

Make the connections as shown in Table 1.

Table 1. Hardware connections

Function	Master			Slave
CLK	WICED_P15	J3.8	D10	WICED_P15	J3.8	D10
MISO	WICED_P14	J3.10	D8	WICED_P14	J3.10	D8
MOSI	WICED_P13	J12.6	A05	WICED_P13	J12.6	A05
CS	WICED_P12	J12.5	A04	WICED_P12	J12.5	A04
GND	GND	J11.6	GND	GND	J11.6	GND

Software setup

Install a terminal emulator if you don't have one. Instructions in this document use Tera Term. All other required software comes bundled with the ModusToolbox™ software.

This example requires no additional software or tools.

Using the code example

Create the project and open it using one of the following:

In Eclipse IDE for ModusToolbox™ software

Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox Application). This launches the Project Creator tool.
Pick a kit supported by the code example from the list shown in the Project Creator - Choose Board Support Package (BSP) dialog.

When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the Quick Panel.

You can also just start the application creation process again and select a different kit.

If you want to use the application for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.
In the Project Creator - Select Application dialog, choose the Bluetooth® SPI_Data_Logger application by enabling the checkbox.
(Optional) Change the suggested New Application Name.
The Application(s) Root Path defaults to the Eclipse workspace which is usually the desired location for the application. If you want to store the application in a different location, you can change the Application(s) Root Path value. Applications that share libraries should be in the same root path.
Click Create to complete the application creation process.

For more details, see the Eclipse IDE for ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/ide_{version}/docs/mt_ide_user_guide.pdf).

Note: Both the dual SPI master and SPI slave sensor applications are created for the same kit that you have selected in Step 2.

In command-line interface (CLI)

ModusToolbox™ software provides the Project Creator as both a GUI tool and the command line tool, "project-creator-cli". The CLI tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the {ModusToolbox™ software install directory}/tools_{version}/project-creator/ directory.

Use a CLI terminal to invoke the "project-creator-cli" tool. On Windows, use the command line "modus-shell" program provided in the ModusToolbox™ software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ software tools. You can access it by typing modus-shell in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.

This tool has the following arguments:

Argument	Description	Required/optional
`--board-id`	Defined in the `<id>` field of the BSP manifest	Required
`--app-id`	Defined in the `<id>` field of the CE manifest	Required
`--target-dir`	Specify the directory in which the application is to be created if you prefer not to use the default current working directory	Optional
`--user-app-name`	Specify the name of the application if you prefer to have a name other than the example's default name	Optional

The following example will clone the "Data Logger" application with the desired name "DataLogger" configured for the CYW920820M2EVB-01 BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CYW920820M2EVB-01 --app-id mtb-example-btsdk-cyw208xx-data-logger --user-app-name DataLogger --target-dir "C:/mtb_projects"

Note: The project-creator-cli tool uses the git clone and make getlibs commands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

In third-party IDEs

Use one of the following options:

Use the standalone Project Creator tool:
1. Launch Project Creator from the Windows Start menu or from {ModusToolbox™ software install directory}/tools_{version}/project-creator/project-creator.exe.
2. In the initial Choose Board Support Package screen, select the BSP, and click Next.
3. In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.
4. Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.

Use command-line interface (CLI):
1. Follow the instructions from the In command-line interface (CLI) section to create the application, and then import the libraries using the make getlibs command.
2. Export the application to a supported IDE using the make <ide> command.
3. Follow the instructions displayed in the terminal to create or import the application as an IDE project.

For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

Operation

Connect two board to your PC using the provided USB cable through the USB connector.
Open a terminal program and select the WICED Peripheral UART port for each board. Set the serial port parameters to 8N1 and 115200 baud.
Program the board using the mtb-example-btsdk-cyw208xx-data-logger application with one of the following:
Using Eclipse IDE for ModusToolbox™ software
1. Select the application project in the Project Explorer.
2. In the Quick Panel, scroll down, and click <Application Name> Program.
  
  Figure 2. Change UART enumeration
  
  Instead of manually setting the UART port in the makefile, you can connect the boards one at a time to program the applications, and then connect both boards when programming is done.
3. Select the application project, CYW208xx_Data_logger.dual_spi_master, in the Project Explorer. In the Quick Panel, scroll down, and click the <Application Name> Program as shown in Figure 3. Repeat this step to program the other board with CYW208xx_Data_logger.spi_slave_sensor and ensure that the UART port selected is for the other board.
  
  Figure 3. Programming the CYW208XX device from ModusToolbox™
Note: If the download fails, it is possible that a previously loaded application is preventing programming. For example, application might use a custom baud rate that the download process does not detect or it might be in a low power mode. In that case, it may be necessary to put the board in recovery mode, and then try the programming operation again from the IDE. To enter recovery mode, first, press and hold the Recover button (SW1), then press the Reset button (SW2), release the Reset button (SW2), and then release the Recover button (SW1).
Using CLI

From the terminal, execute the make program command to build and program the application using the default toolchain to the default target. The default toolchain and target are specified in the application's Makefile but you can override those values manually:
```
make program TARGET=<BSP> TOOLCHAIN=<toolchain>
```
Example:
```
make program TARGET=CYW920819EVB-02 TOOLCHAIN=GCC_ARM
```

After programming, the application starts automatically. Confirm that is displayed on the UART terminal and it will start advertising.

Configure the terminal application to access the serial port using settings listed in Table 2.

Table 2. WICED peripheral UART settings

WICED peripheral UART serial port configuration	Value
Baud rate	115200 bps
Data	8 bits
Parity	None
Stop	1 bit
Flow control	None
New-line for receive data	Line feed (LF) or auto setting

The slave serial terminal window displays the received SPI command and the accompanying response on the terminal window, as shown in Figure 4.

Figure 4. Serial terminal output of SPI slave
The master serial terminal window displays a message that prompts you to press the User button (SW3) to view the temperature records. When you press the button, and if there are no temperature records to be read from SFLASH, an appropriate message is displayed on the window. Otherwise, the temperature records that have not already been read are displayed on the terminal window as shown in Figure 5.

Figure 5. Serial terminal output of SPI master

The master stores, in the NVRAM, the number of records that were last stored in the SFLASH. This feature ensures that even when the master is powered down or reset, prior temperature records are not lost by overwriting the previous data. You can test this feature by pressing the Reset button (SW2), and then the User button (SW3). The terminal displays all the stored temperature records from the beginning as shown in Figure 6.

Note: The RTC timestamp value is reset for the new values that are stored, so there will not be continuity in the timestamp values between the stored records before reset and the stored records after reset.

Figure 6. Serial terminal output of SPI master after reset

Design and implementation

SPI master

This section describes the details of the implementation of the SPI master.

On startup, the application sets up the UART and then starts the Bluetooth® stack in application_start(). Once the stack is started (BTM_ENABLED_EVT), it calls the initialize_app() function, which handles the remaining functionality. Note that the Bluetooth® stack is running; since Bluetooth® is not used in this application, it does not do anything once the stack is started. The initialize_app() function initializes both the SPI interfaces, RTC, GPIO, and two separate threads which handle two different SPI transactions – one to read the SPI sensor and another to write the SFLASH. The two threads communicate with each other through a queue to transfer temperature records. A semaphore is used to signal the thread handling SFLASH, when data of one page size is available in the queue for writing. In this implementation, the page size is 256 bytes and the size of each temperature record is 16 bytes, so records are written when 256/16 = 16 temperature values have been received.

Also, during initialization the number of the last record that was stored in NVRAM is obtained. The NVRAM read provides the number of temperature records that are present in SFLASH, so that if the master is reset or powered down, the current address (that is, where new temperature records will be written) is updated to address of the next free location. This prevents overwriting of stored temperature records upon reset. When the application is running for the first time after download, the NVRAM read fails since no write has been performed. Here, the record number read from NVRAM is re-assigned to 0 to prevent using an erroneous value for the record number.

The temperature readings are held in a structure called temperature_record, which contains the following elements:

record_no : Stores the number of temperature records
dec_temp : Holds the decimal part of the temperature reading
frac_temp : Holds the fractional part of the temperature reading
timestamp : Holds the time when temperature reading was received. Note that the timestamp values, by default, start from 00:00:00 hrs, January 1, 2010.

In the thread handling SPI communication with the slave (spi_sensor_thread), a finite state machine is used to determine the data that the master requests, as shown in Figure 7.

Figure 7. Finite state machine adopted for communicating with slave

The finite state machine contains three states:

SENSOR_DETECT
READ_UNIT
READ_TEMPERATURE

In each state, the slave is verified to be a known slave using a packet header before processing the data that is sent from the slave. If the master is not able to authenticate the slave, the master remains in the same state and retries. After five attempts, the SPI interface is reset, and the master starts from the SENSOR_DETECT state.

In the SENSOR_DETECT state, the master requests the manufacturer ID to verify whether the slave’s manufacturer is Cypress. If the slave responds with an unknown manufacturer ID, the master informs the user that the slave’s identity could not be authenticated. If the slave responds with the expected manufacturer ID, the master enters the next state, READ_UNIT. A flowchart illustrating the operation is shown in Figure 8.

Figure 8. Flowchart of the SENSOR_DETECT state

In the READ_UNIT state, the master requests the unit ID to know the unit of temperature values provided by the slave. If the slave responds with an unknown unit ID, the master informs the user that the unit of temperature is unknown and tries to obtain the unit again. If the number of attempts exceeds five, the master changes its state to SENSOR_DETECT. Otherwise, if the slave responds as expected, the master enters the next state, READ_TEMPERATURE. A flowchart illustrating the operation is shown in Figure 9.

Figure 9. Flowchart of the READ_UNIT state

In the READ_TEMPERATURE state, the master requests the temperature from the slave. The temperature reading received comprises the decimal and fractional parts of the temperature. For instance, if the temperature reading is 24.44 °C, the slave sends 2444 as the data. The master then stores the quotient as the decimal part of temperature and remainder as the fractional part of temperature in the temperature record. The RTC is used to obtain the time when the temperature reading was received so that it can be included in the temperature record. The number of the temperature record is also updated and pushed to the queue. The queue occupancy is checked every time after a temperature record is pushed to the queue. Once the queue occupancy equals the size of a page in SFLASH, the thread sets a semaphore signaling the thread handling SFLASH to start popping data from queue to write to SFLASH. A flowchart illustrating the operation is shown in Figure 10.

Figure 10. Flowchart of the READ_TEMPERATURE state

The thread handling SFLASH (sflash_thread) performs an erase if the current page being written to belongs to a new sector and waits for the semaphore to be set. Once the semaphore is set, it pops the data from the queue and writes it to SFLASH. The size of the data written is one page (256 bytes), which is 16 temperature records. The size of the data written is chosen as one page to maximize efficiency of the write operation. The record number of the last temperature record that was stored in SFLASH is written to NVRAM in this thread after every page write.

The application level source files for dual_spi_master is listed in Table 3.

Table 3. Application source files

File name	Description
dual_spi_master.c	Contains the `application_start()` function, which is the entry point for execution of the user application code after device startup and the threads that handle SPI communication with sensor and SFLASH.

SPI slave

This section describes the operation of the slave. As with the master, application_start() sets up the UART and then starts the Bluetooth® stack. Once the stack is started (BTM_ENABLED_EVT), it initializes the ADC and then calls the initialize_app() function, which handles the remaining functionality. Note that the Bluetooth® stack is running; since Bluetooth® is not used in this application, it does not do anything once the stack is started. The initialize_app() function sets up the SPI interface, initializes the thermistor and then waits for and responds to SPI master commands. There are three commands that the slave will respond to:

Manufacturer ID: The slave responds with its manufacturer ID.
Unit ID: The slave responds with its unit ID.
Temperature: The slave responds with a temperature reading obtained by acquiring ADC samples.

The slave reads from SPI Rx buffers only, when its Tx buffers are empty. If the slave is unable to empty the Tx buffers after several attempts, the SPI interface is reset. A flowchart illustrating the operation of the slave is shown in Figure 11.

Figure 11. Flowchart showing the slave operation

The application level source files for spi_slave_sensor are listed in Table 4.

Table 4. Application source files

File name	Description
spi_slave_thermistor.c	Contains the `application_start()` function, which is the entry point for execution of the user application code after device startup.
thermistor_temp_db.c, thermistor_temp_db.h	Contain the function to map resistance to temperature values of the thermistor using a lookup table (from the thermistor datasheet).

Related resources

Resources	Links
Application notes	AN225684 – Getting started with CYW208xx
Code examples	Using ModusToolbox™ software on GitHub Using Bluetooth® SDK
Device documentation	CYW20819 device datasheet CYW20820 device datasheet
Development kits	Visit https://www.infineon.com/cms/en/product/wireless-connectivity/airoc-bluetooth-le-bluetooth-multiprotocol
Libraries on GitHub	btsdk-drivers – Bluetooth® SDK drivers library btsdk-mesh – Bluetooth® LE mesh libraries btsdk-ota – Bluetooth® LE OTA libraries btsdk-ble – Bluetooth® LE profile libraries
Tools	Eclipse IDE for ModusToolbox™ software – ModusToolbox™ software is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC™ Wi-Fi and Bluetooth® connectivity devices. btsdk-utils – Bluetooth® SDK utilities btsdk-peer-apps-ota – Bluetooth® LE OTA peer applications btsdk-host-peer-apps – Bluetooth® LE mesh host and peer applications btsdk-host-apps-bt-ble – Bluetooth® and Bluetooth® LE host applications

Other resources

Cypress provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.

Document history

Document title: CE226537 – Bluetooth® SPI-based datalogger

Version	Description of change
1.0.0	New code example
1.1.0	Updated to support ModusToolbox™ software v2.1
2.0.0	Major update to support ModusToolbox™ software v2.2 This version is not backward compatible with ModusToolbox™ software v2.1
3.0.0	Updated to support ModusToolbox™ software v2.3.1, BTSDK 3.0 and Updated Thermistor library
3.1.0	Added support for CYW920820M2EVB-01
3.2.0	Added support for CYW920819M2EVB-01

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