SimplePublish for SAM C21 Xplained Pro
The QSL includes a SimplePublish example for the Atmel SAM C21 Xplained Pro evaluation kit. This is given as an Atmel Studio 7 project based on the Atmel Software Framework (ASF). The main.c code itself is similar to the one for the Raspberry Pi, with the addition of a watchdog timer and initialization of a second serial port to enable debug prints (the watchdog is for demonstration purposes only, and can be removed as the user see fit).
The example was developed on Atmel Studio Version 7.0.1006 with ASF version 3.32.0.
Download Atmel Studio 7
Download and run the Atmel Studio web installer from the official download page, and follow the instructions. This will also install the necessary drivers for the embedded debugger on the Xplained Pro board.
Windows is the only supported OS for the latest Atmel Studio 7.
ASF is included in Atmel Studio 7 and does not require a specific download, but you can use the Extension Manager (Tools->Extension Manager) to update it.
Prepare the SAM C21 Xplained Pro
Set Supply Voltage to 3.3 V
Make sure that the jumper on the 3-pin header labeled VCC_SEL is set to 3.3 V, as seen in Figure 5. This will select 3.3 V as the supply voltage for the ATSAMC21J18A, peripherals and extension headers, which is important as we will power the mote from the latter.
The supply voltage is by default set to 5.0 V, which will fry your mote instantly!
Figure 5: Xplained Pro VCC selection header.
Connect to Mote
Figure 6: Mote connected to the SAM C21 Xplained Pro.
The Xplained Pro has three extension headers (EXT1, EXT2, EXT3) with pins as listed in Table 7: Connect the mote to one of the headers, as per the mapping in Table 8. In Figure 6 you can see the mote connected to EXT1, but it does not matter which one you use: The pins for UART RX/TX on all three headers are connected to the same pins on the SAM C21.
Long cables between the mote and Xplained Pro may corrupt the API bus communication.
Name | Pin # | Name | |
|---|---|---|---|
| ID | 1 | 2 | GND |
| ADC+ | 3 | 4 | ADC- |
| GPIO0 | 5 | 6 | GPIO1 |
| PWM+ | 7 | 8 | PWM- |
| IRQ | 9 | 10 | SPI_SS_B |
| TWI_SDA | 11 | 12 | TWI_SCL |
| UART_RX | 13 | 14 | UART_TX |
| SPI_SS_A | 15 | 16 | SPI_MOSI |
| SPI_MISO | 17 | 18 | SPI_SCK |
| GND | 19 | 20 | VCC |
Table 7: Xplained Pro Standard Extention Header.
Xplained Pro | Mote |
|---|---|
| VCC | VBAT |
| GND | GND |
| UART_TX | RX |
| UART_RX | TX |
| GND | RX RTSn |
| GND | TX CTSn |
Table 8: Xplained Pro to mote pin mapping.
Connect Debug USB to Computer
Connect a USB cable from your computer to the USB-micro port labeled DEBUG USB: This is the port on the top of the Xplained Pro board (visible in both Figure 5 and Figure 6), and is used to program, debug and power the board.
The debug USB also spawns a virtual serial port named EDBG Virtual COM Port. Make sure to note the name, e.g. COM4 in the example pictured below, as we will open a terminal on said port to see debug prints.
Open Debug Terminal
The SimplePublish example code will send all standard input/output (e.g. debug prints) through the serial port you identified in the previous section. Open your favourite serial terminal (e.g. Putty) and connect to said serial port with the following configuration:
- Baudrate: 115200
- Data Bits: 8
- Parity: None
- Stop Bits: 1
You probably have to restart the terminal whenever you disconnect/reconnect the debug USB to the Xplained Pro.
Compile and Run
Navigate to the SimplePublish example directory at examples/samc21_xplained_pro/SimplePublish and open the SimplePublish.atsln solution file in Atmel Studio 7. This should open the project with everything set up for you. Since the Xplained Pro has an embedded debugger, you do not have to select any tool: Atmel Studio should detect that the board is connected via USB.
Now, simply press the 
symbol (Ctrl+Alt+F5) to compile and run the program, and you should see prints appearing on the debug terminal you opened.
Port to Similar Platforms
Although the provided code is written specifically for the ATSAMC21J18A on the SAM C21 Xplained Pro evaluation kit, it should be pretty straightforward to port it to similar architectures that support the same ASF modules. Correctly configuring the available serial ports (SERCOM) in serial.c/.h should be the only thing that might require some adaptation. We therefore give a quick guide on how to set up a new ASF project.
Create New Project
- File > New > Project... (Ctrl+Shift+N)
- Under C/C++, select GCC C ASF Board Project.
- Select project name and location of your choice
- Solution: Create new solution.
- (Optional) Check the Create directory for solution box if you want to place the project folder within a solution directory that you also have to provide a name for.
- Press Ok
- Select the correct device and board, and press Ok.
Add ASF Modules
- Open the ASF Wizard: ASF > ASF Wizard (Ctrl+W)
- Select the correct project in the drop down menu (if not already selected).
You should now see two windows with Available vs Selected Modules. Select and Add >> all the modules listed in Table 9.
Make sure to select the correct mode when adding certain modules (you can change the mode of already selected modules too).
Press Apply.
Name | Type | Mode | Comment |
|---|---|---|---|
| Generic board support | Driver | Selected by default | |
| Delay routines | Service | cycle | Used to implement dn_sleep_ms |
| PORT - GPIO Pin Control | Driver | Selected by default | |
| RTC - Real Time Counter Driver | Driver | count_polled | Used to implement dn_time_ms |
| SYSTEM - Core System Driver | Driver | Selected by default | |
| WDT - Watchdog Timer | Driver | callback | Used to implement watchdog functionality (optional) |
Table 9: ASF modules used in the SimplePublish example code.
Add QSL and C Library as Link
Create folder
Add as link
Add to Directories in Toolchain
Restart Atmel Studio (Directory Bug...)
Add Platform Specific Files
Add as copy
Make necessary adaptations