Step 2.1: Configure I²C Driver and I²C pins
1
Under the Device Resources tab, expand Harmony > Drivers > I²C.
- Select and double click on I²C to add the I²C driver to the project.
Select FreeRTOS and view the Configuration Options on the right. Depending on the requirements of the application, the FreeRTOS™ default configuration can be changed using the GUI. For this tutorial, you will use the default configuration.
Adding FreeRTOS maps all the Operating System Abstraction Layer (OSAL) Application Programming Interface (API) calls used by the MPLAB ® Harmony drivers and system services to FreeRTOS APIs.
- Associate I²C driver with I²C instance 0 (TWIHS0) peripheral by right clicking on the red diamond.
- Click on Instance 0 under I²C Driver to view the Configuration Options. Change the Number of Clients to 2.
- The above configuration allows the same instance of driver to be used by two different clients. The first application client interfaces with the Temperature Sensor thread and the second application client interfaces with the EEPROM thread.
- The Number of Clients for each driver instance is automatically set to one. MPLAB Code Configurator (MCC) assumes a minimum of one client for each instance of the driver.
If the application had two or more devices that were interfaced through different I²C peripherals, then the driver had to be configured to enable multiple instance support. Multiple instance support is enabled by clicking on the + sign on the I²C driver block. Every click on the + sign adds a new instance to the driver. Each instance can be configured separately.
- Click on I²C to verify the driver is configured in Synchronous mode.
- Select TWIHS0 Peripheral Library and notice the default configuration by expanding Hardware Settings.
The TWIHS0 (I²C) retains the default 400 kHz speed because the temperature sensor chip and EEPROM on I/O1 Xplained Pro Extension Kit can operate at 400 kHz I²C speed.
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Open the Pin Configuration tabs by clicking Project Graph > Plugins > Pin Configuration.
3
Select the Pin Settings tab and sort the entries by Ports as shown below.
Now, select the Pin Table tab and then scroll down to the TWIHS0 module as shown below.
- Enable I²C Clock (TWIHS0_TWCK0) on PA04 (Pin #77).
- Enable I²C Data (TWIHS0_TWD0) on PA03 (Pin #91).
This completes the configuration of the I²C driver. The application code will use the I²C driver APIs to read the temperature from the temperature sensor and store it in EEPROM. The application also retrieves last five temperature values stored in the EEPROM.
Step 2.2: Configure Universal Synchronous Asynchronous Receiver Transmitter (USART) Driver and USART pins
1
Under the Device Resources tab, expand Harmony > Drivers > SQI Flash > USART.
- Double click on USART to add the Universal Synchronous Asynchronous Receiver Transmitter (USART) driver to the project.
- Associate USART Driver with USART instance 1 (USART1) peripheral by right clicking on the red diamond.
- Verify USART driver is configured to run in Synchronous mode by clicking on the USART block as shown below
- Click on Instance 0 under USART Driver to view the Configuration Options. Change the number of clients to the USART driver Instance 0 to 3. The User Input Thread will use the USART driver to read the character input on the serial terminal. The Sensor and EEPROM threads will use the USART driver to print temperature values on the serial terminal.
- Select the USART1 Peripheral Library in the Project Graph and configure it for USART protocol, including setting the baud rate to 115200 Hz.
2
Select the Pin Table tab and then scroll down to the USART1 module as shown below.
Enable USART_TX (USART1_TXD1) on PB04 (Pin #105).
Enable USART_RX (USART1_RXD1) on PA21 (Pin #32).
The application will use the USART driver for printing messages on the serial terminal and receiving input from the user to retrieve the last five stored values from the EEPROM.