In this exercise students will explore a Freescale Cup Car application which targets a Freescale K40 board attached to the Tower System.
To successfully complete this exercise, students will need the following board and development environment.
Read the Blink LED overview article for general information on LED circuits, GPIO pins and reference manuals.
There are several steps necessary to prepare the evaluation board and PC for microcontroller programming and development. Interfacing the evaluation board with a PC requires downloading and Install the CodeWarrior IDE, as well as the device drivers for programming the microcontroller via USB.
In addition to CodeWarrior, it may(needs verified) be necessary to install one or both of the following tools:
There are several Twr K40x256 hardware configuration steps. Follow the twr-k40x256-hardware-setup instructions before importing the LED Project.
After the software is successfully downloaded and installed, the next step is to import an existing project into your Workspace. in this case, the LED_BLINK_96MHZ Project. Follow the instructions on the codewarrior-project-import page to import the LED_BLINK_96MHZ project into CodeWarrior.
If errors are encountered, look in the Problems view and resolve them. Ignore any warnings.
If there is more than one project in your project view, make sure the proper project is the focus. The most reliable way to do this is to right click the project and choose Build Project as shown below. You can also go to the Project menu and choose the same command.
By default, the application is set to link to RAM. If you want your program in FLASH, make sure that you have that build configuration enabled:
Make sure you do a "Clean" operation (under the project menu) after you make the configuration change.
If you encounter errors, look in the problems view and resolve them. You can ignore any warnings.
If the project builds correctly, it is time to download to the board and watch it work. Ensure that the USB cable that came with the board connects the board to the host computer’s USB port.
There are multiple ways to issue the Debug command. Right click the project in the projects view and choose Debug As->CodeWarrior Download. Alternatively, y go to the Run menu and choose Debug (F11).
If the LED was on Port C, Bit 7 we might have code like:
For example, to toggle a pin the following code might be used:
"Sets" the LED located at "E1" high.
the syntax means the following GPIOC refers to Port C
"Set" is one of three commonly utilized commands for GPIO control. There are also commands for "Clear" and "Toggle."
the « is a "shift" command which is discussed in the c-programming-for-embedded-systems. You can alter the raw register as well using a MASK but the dedicated set/clear/toggle registers are more straightforward.
**NEEDS UPDATED **
The following functions can access the LED;
//Where n is the LED number
LED_En_TOGGLE; //will toggle a LED to a different state
LED_En_ON; // turns the LED ON
LED_En_OFF // turns the LED OFF
Locations of the LED's
//The E1 LED is on Port C, Bit 7
#define LED_E1_LOC (1<<7)
#define LED_E2_LOC (1<<8)
#define LED_E3_LOC (1<<9)
#define LED_E4_LOC (1<<11)
//There are dedicated set and clear registers.
//Write a one to PSOR Sets the Bits, Writing to PCOR clears bits.
//Toggling a bit can be done with the PTOR register
//You can access the raw register as well -> PDOR |= My Bit
//but the dedicated bit set/clear/toggle registers are easier!
//Also, The cathode of the LEDs are towards the port pin! This means
//you have to turn the port off to get the LED to turn the pin on.
#define LED_E1_OFF GPIOC_PSOR=LED_E1_LOC
#define LED_E1_ON GPIOC_PCOR=LED_E1_LOC
#define LED_E1_TOGGLE GPIOC_PTOR=LED_E1_LOC
#define LED_E2_OFF GPIOC_PSOR=LED_E2_LOC
#define LED_E2_ON GPIOC_PCOR=LED_E2_LOC
#define LED_E2_TOGGLE GPIOC_PTOR=LED_E2_LOC
#define LED_E3_OFF GPIOC_PSOR=LED_E3_LOC
#define LED_E3_ON GPIOC_PCOR=LED_E3_LOC
#define LED_E3_TOGGLE GPIOC_PTOR=LED_E3_LOC
#define LED_E4_OFF GPIOB_PSOR=LED_E4_LOC
#define LED_E4_ON GPIOB_PCOR=LED_E4_LOC
#define LED_E4_TOGGLE GPIOB_PTOR=LED_E4_LOC
SIM_SCGC5 = SIM_SCGC5_PORTA_MASK | SIM_SCGC5_PORTB_MASK | SIM_SCGC5_PORTC_MASK | SIM_SCGC5_PORTD_MASK | SIM_SCGC5_PORTE_MASK;
//To use a Port, its Clock must be enabled!!
//Lets just enable the clocks for ALL of the ports
//Important! Each IO pin has a dedicated 32-bit Register to set it up (Selection GPIO vs peripheral, IRQ, Etc.)
//Setup port C7,C8,C9 and B11 as GPIO and enable High Drive Strength
PORTC_PCR7 = PORT_PCR_MUX(1) | PORT_PCR_DSE_MASK; //Enable GPIO on on the pin
PORTC_PCR8 = PORT_PCR_MUX(1) | PORT_PCR_DSE_MASK; //Enable GPIO on on the pin
PORTC_PCR9 = PORT_PCR_MUX(1) | PORT_PCR_DSE_MASK; //Enable GPIO on on the pin
PORTB_PCR11 = PORT_PCR_MUX(1) | PORT_PCR_DSE_MASK; //Enable GPIO on on the pin
PORTC_PCR18 = PORT_PCR_MUX(1) | PORT_PCR_DSE_MASK;
PORTE_PCR28 = PORT_PCR_MUX(1) | PORT_PCR_DSE_MASK;
//Make Sure the GPIO is setup to be an output
GPIOC_PDDR |= LED_E1_LOC | LED_E2_LOC | LED_E3_LOC;
GPIOB_PDDR |= LED_E4_LOC;
Within Main.c or any other C file created, Blink the LED's using the following functions:
Some of the content from this tutorial originated from:
Shawn Moffit: Electrical Engineering, Penn State University
for - K40 Code
Processor Expert Hands-On Lab Rev. 1.0, 05/2011
by Jim Trudeau, Freescale Semiconductor, Inc.
for - some text descriptions of steps
Original Attachment has been moved to: LED_BLINK_96MHZ.zip