Arm® TrustZone® Technology Getting Started Application on PIC32CK SG01: Step 2

Last modified by Microchip on 2024/03/26 10:36

  

Configure Secure Real-Time Clock (RTC) Peripheral Library

Under the bottom left Device Resources tab, expand Harmony > Peripherals > RTC.

Double-click or drag and drop RTC to add the RTC Peripheral Library (PLIB) to the Project Graph.

MCC window illustrating adding the RTC Peripheral Library to the Project Graph

Figure 1

 

In the Clock Easy view, verify the RTC clock is set to run at 1 kHz internal ultra-low-power clock.

When a module is added to the Project Graph, MPLAB® Code Configurator (MCC) automatically enables the clock to the module. The default RTC clock source is an internal 1 kHz ultra-low-power clock (OSCULP1K).

RTC verification in Clock Easy view

Figure 2

Note: On the PIC32CK SG01 device, the RTC can be clocked through several low power clock sources of 1 kHz and 32 kHz as shown in Figure 2. The 1 kHz clock source retained (OSCULP1K) is enough to generate time periods of 500 milliseconds, 1 second, 2 seconds, and 4 seconds.

Go back to the Project Graph and configure the RTC PLIB to generate a compare interrupt every 500 milliseconds.

Configure the RTC PLIB

Figure 3

Note: The Compare Value is set as 0x200. This compare value generates an RTC compare interrupt every 500 milliseconds

  • RTC clock = 1024 Hz
  • RTC Prescaler = 1
  • Required Interrupt rate = 500 ms

Hence, Compare Value = (500/1000) x 1024 = 512 (i.e., 0x200).

Back to Top

Configure Secure I²C Peripheral Library and Secure I²C pins

Under the Device Resources tab, expand Harmony > Peripherals > SERCOM.

Double-click on SERCOM4 to add the SERCOM instance 4 to the project.

Double click on SERCOM1 to add the SERCOM instance 4 to the project

Figure 4

Select the SERCOM 4 Peripheral Library and configure it for the I²C protocol as shown in Figure 5.

Configure SERCOM 1 Peripheral Library

Figure 5

​

Note:

  • The SERCOM4 (as I²C) retains the default 100 kHz speed because the temperature sensor chip on I/O1 Xplained Pro Extension Kit can operate at 100 kHz I²C speed.
  • The SERCOM4 (as I²C) retains the default 50-100 nanoseconds hold time for Serial Data (SDA) Hold Time because it aligns with the minimum (50 nanoseconds) start hold time specified in the specification of the temperature sensor chip (AT30TSE758).
  • The SERCOM4 (as I²C) retains the default 100 nanoseconds for I²C Trise time because it aligns with the maximum (300 nanoseconds) input rise time specified in the specification of the temperature sensor chip (AT30TSE758).

Open the Pin Configuration tabs by clicking Project Graph > Plugins > Pin Configuration.

Open the Pin Configuration tab

Figure 6

Select the Pin Settings tab and sort the entries by Ports, as shown in Figure 7.

Select the Pin Settings tab

Figure 7

Now, select the Pin Settings tab and then scroll down to the SERCOM4 module as follows:

  • Enable I²C Data (I²C_SDA) (SERCOM_PAD0) on PB09 (Pin #71) as Secure mode.
  • Enable I²C Clock (I²C_SCL) (SERCOM_PAD1) on PB10 (Pin #72) as Secure mode.
Configure pins 17 and 18

Figure 8

This completes the configuration of the I²C peripheral library. The application code will use the I²C PLIB Application Programming Interfaces (APIs) to read temperature from the temperature sensor.

Back to Top

Configure Non-Secure Universal Synchronous Asynchronous Receiver Transmitter (USART) Peripheral Library and USART pins

Under the tab Device Resources tab, expand Harmony > Peripheral > SERCOM.

Double-click on SERCOM5 to add the SERCOM instance 5 to the project.

Double click on SERCOM5 to add the SERCOM instance 5 to the project

Figure 9

Select the SERCOM5 Peripheral Library in the Project Graph and verify default SERCOM Operation Mode configuration is set as USART. Configure it as shown in Figure 10.

Configuration Options tab

Figure 10

Verify the default baud rate is set to 115200 Hz.

Note:

  • SERCOM5 (as USART) interrupt is disabled because Direct Memory Access (DMA) will be used (configured in the following steps) to transfer application buffer to the USART TX register and also recieves data from USART RX register.
  • As per the "PIC32CK SG01 Curiosity Ultra Development Board" design, SERCOM5 PAD0 and SERCOM5 PAD1 are used for SERCOM5 (as USART) data transmission and reception.
  • The application will use the SERCOM5 (as USART) PLIB for printing messages on the serial terminal and reads a character from serial terminal as a user request to read last five stored temperature values from EEPROM.

Select the Pin Settings tab and then scroll down to the SERCOM5 module.

  • Enable USART_TX (SERCOM_PAD0) on PA24 (Pin #17) as NonSecure Mode.
  • Enable USART_RX (SERCOM_PAD1) on PA25 (Pin #20) as NonSecure Mode.
Pin Settings tab

Figure 11

Back to Top

Configure Non-Secure DMA Peripheral Library

Configure DMA by selecting the System block in the Project Graph. In Configuration Options navigate to DMA. 

Configuration Options tab

Figure 12

Expand DMA 

  • Enable DMA Channel 0.

  • Enable DMA Channel 1.
    Configuration Options tab

    Figure 13

  • Expand DMA Channel 0 and configure it to transmit the application buffer to the USART TX register. The DMA transfers one byte from the user buffer to the USART transmit buffer on each trigger.
  • Expand DMA Channel 1 and configure it to receive the USART RX register data to the application receive buffer. The DMA transfers one byte from the USART receive buffer to the user buffer on each trigger.
Configuration Options tab

Figure 14

Based on the trigger source, the DMA channel configuration is automatically set by MCC.

  • Trigger Action: Action taken by DMA on receiving a trigger.
    • Cell Transfer: The number of bytes transferred when a DMA channel has a transfer initiated before waiting for another event. A cell transfer is comprised of one or more transactions. Generally used during a memory-to-peripheral or peripheral-to-memory transfer.
    • Block transfer: The number of bytes transferred when a channel is enabled. The number of bytes is the larger of either Source or Destination size. A block transfer is comprised of one or more cell transfers. Generally used during the memory-to-memory transfer on a software trigger.
  • Source Address Mode, Destination Address Mode: Select whether to increment the Source/Destination Address after every transfer. Automatically set by MCC based on the trigger type. For example:
    • If the trigger source is USART transmit, then the Source Address is incremented, and the Destination Address is fixed.
    • If the trigger source is USART receive, then the Source Address is fixed, and the Destination Address is incremented.

Note:

  • USART transmit buffer empty event triggers DMA to transfer one byte of data from source (user buffer) to destination (USART Tx register). When all the requested bytes are transmitted, DMA PLIB notifies the application by calling the registered DMA callback event handler.
  • USART receive timeout event triggers DMA to transfer one byte of data from the source (USART Rx register) to the destination (user buffer). When all the requested bytes are received, DMA PLIB notifies the application by calling the registered DMA callback event handler.

Launch NVIC Configuration by selecting Project Graph > Plugins > NVIC Configuration.

Project Graph tab

Figure 15

Click on the NVIC Settings tab. Verify that the DMA0_PRI1 (DMA Channel 0) and DMA0_PRI2 (DMA Channel 1) as NON-SECURE projects.

NVIC Configuration tab

Figure 16

Back to Top