キーワード: low-power microcontroller, IR carrier frequency generation, IR carrier modulation, IAR software, IAR Embedded Workbench
The MAXQ622 is a low-power microcontroller from Maxim Integrated Products. It is designed for battery-powered applications and offers low active-mode current (3.75mA typical at 12MHz). The microcontroller also features a highly efficient 16-bit single-cycle RISC processor core and flexible clocking schemes that help dynamically control performance and power consumption. The MAXQ622 is ideal for applications that require a large number of I/O pins and low power consumption.
The MAXQ622 includes a number of important features:
The MAXQ622 evaluation (EV) kit provides a proven, reliable platform for developing low-power applications for the MAXQ622 processor. The kit includes: an IR transmitter and receiver, a USB port, 8 pushbuttons for user input, 4 LEDs for application usage, a prototyping area, and headers for accessing all the MAXQ622's I/O pins. Additionally, the provided jumpers allow convenient monitoring of the MAXQ622 processor's actual power consumption during operation.
Figure 1 shows the MAXQ622 evaluation kit (EV kit) board. The EV kit contains the following hardware components:
Use these components to implement and verify the demonstration program in this application note.
Figure 1. MAXQ622 EV kit.
The MAXQ622 EV kit board has a number of jumpers to configure. For this application note, the jumpers should be configured to match the default settings, as shown in Table 1.
Table 1. Jumper Configuration for the MAXQ622 EV Kit Board
|JH1||Open||Disconnects the board’s DS1 LED cathode from the MAXQ622’s port pin P3.0.|
|Closed*||Connects the board’s DS1 LED cathode to the MAXQ622’s port pin P3.0.|
|JH2||Open||Disconnects the board’s D1 LED IR emitter from the MAXQ622’s IRTX pin.|
|Closed*||Connects the board’s D1 LED IR emitter to the MAXQ622’s IRTX pin.|
|JH3||Open||Disconnects the board’s DS2 LED cathode from the MAXQ622’s port pin P3.1.|
|Closed*||Connects the board’s DS2 LED cathode to the MAXQ622’s port pin P3.1.|
|JH4||Open||Disconnects the board’s DS3 LED cathode from the MAXQ622’s port pin P3.2.|
|Closed*||Connects the board’s DS3 LED cathode to the MAXQ622’s port pin P3.2.|
|JH5||Open||Disconnects the board’s DS4 LED cathode from the MAXQ622’s port pin P3.3.|
|Closed*||Connects the board’s DS4 LED cathode to the MAXQ622’s port pin P3.3.|
|JH6||Open||Disconnects the board’s D2 LED IR receiver amplified signal from the MAXQ622’s IRRX pin.|
|Closed*||Connects the board’s D2 LED IR receiver amplified signal to the MAXQ622’s IRRX pin.|
|JH7||Open||Disconnects the IR Rx enable from the MAXQ622’s P0.7 pin.|
|Closed*||Connects the IR Rx enable to the MAXQ622’s P0.7 pin.|
|JH8||1-2 Closed*||Powers the MAXQ622’s VBUS supply from the USB VBUS supply (connected at CN1).|
|2-3 Closed||Powers the MAXQ622’s VBUS supply from the +5.0V DC supply connected at J2.|
|JH9||1-2 Closed*||Power the MAXQ622’s VDD supply from the output of the +3.3V fixed regulator.|
|2-3 Closed||Powers the board through JH9.2 (power) and JH9.3 (ground).|
|JH10||Open||Disconnects the USB VBUS supply (from CN1) to the input to the +3.3V regulator.|
|Closed*||Connects the USB VBUS supply (from CN1) to the input to the +3.3V regulator.|
|JH11||Open||Disables the DS5 power LED.|
|Closed*||Enables the DS5 power LED.|
A USB-to-JTAG/1-Wire adapter has been included with the EV kit to program the MAXQ622. The installation guide for the adapter is available for download.
After installing the USB-to-JTAG/1-Wire adapter, connect the JTAG cable to the MAXQ622 EV kit board. The red stripe on the cable should connect to the side of the connector labeled pin 1 and pin 2 on the JTAG board and to the side of the connector labeled TCK-GND on the MAXQ622 EV kit board.
The IAR Embedded Workbench® is the primary IDE used for coding in C with the MAXQ622. The latest version can be obtained from our website. IAR™ offers both time-limited and size-limited licenses of the IDE for evaluation. Download and execute the installer. Follow the directions to install the software.
After installing the software, open the application and create a new project in the current workspace. Ensure that the MAXQ tool chain is selected from the drop-down list, and open a new C project with a generated main.c file (Figure 2).
Figure 2. IAR new project wizard.
To configure the project to run on the MAXQ622, select Options from the Project menu or press ALT+F7. Select MAXQ622 from the device drop-down menu and ensure that CLIB is selected under the Library Configuration tab (Figure 3).
Figure 3. IAR Embedded Workbench project configuration.
Once the target device is selected, assign the com port that the JTAG adapter is using by inputting the string referencing the com port in the text field provided (Figure 4). Note: Use the System Device Manager to verify the com port setting.
Figure 4. IAR JTAG settings.
The workspace maxq622evkit.eww includes sample projects that are viewable in the Workspace window. Configure each project in the workspace to match the MAXQ622 by following the above steps. The projects are now ready to be compiled, loaded, and debugged on the EV Kit.
For this application note example, activate the gpio project from the Workspace tab and ensure that the project settings described above have been properly configured. To view the source code for the project, double-click on the file gpio.c. The file isr.c is not used in this project, but it contains the interrupt callback functions for other projects included with the EV kit. To begin debugging the project, click the Debug button or press Ctrl + D. This action automatically compiles the source code and loads it onto the MAXQ622. The default debug settings will automatically place a breakpoint at the main function (Figure 5).
Figure 5. IAR debug.
From here, navigate through the program using the Debug toolbar functions. To set more breakpoints throughout the code, double-click in the margin to the left of the line to place a break in the program (Figure 6).
Figure 6. IAR breakpoints.
The gpio example uses a timer on the MAXQ622 to blink 4 LEDs. The first four pins are wired to these LEDs and can be manipulated by the software. By shifting the mask variable, the position of the high bit will move through the mask to the bit for each LED (Figure 6). The PD3 register controls the direction of the port 3 pins. Setting these bits to 1 configures them for output, allows the voltage to be raised high, and turns on the LEDs.
A timer in the MAXQ622 is then used to control the blink rate of the LEDs. The timer initializes to count at a constant rate (Sysclk/256) from 0 up to 0xB71B. The default Sysclk is 12MHz, making the timer raise its flag every second (Figure 7).
Figure 7. Timer Initialization.
The IAR software allows the user to view variable and register values while debugging. In order to look at a register or variable, right-click on the expression and select Add to Watch. When a breakpoint halts execution or the Break button is pressed, these values are updated and can be changed by the user (Figure 8). Also, view registers by selecting the View menu and clicking Register.
Figure 8. blinkLED() function/IAR Register and Watch.