Summary

In the previous articles I discussed using the FRAM, and making a FreeRTOS FAT SL media driver.  In this article I will discuss building an example project that uses that work to make a real FreeRTOS FAT SL system example.  I was originally planning on making just one article explaining the example, but my example code turned out to be a little bit sprawling, so I decided to break it into two pieces.  In part 1 (this article) I will

  1. Build the FreeRTOS Template
  2. Import the FreeRTOS FAT SL FileSystem & FRAM Media Driver
  3. Build a command line interpreter
  4. Nuke the data in the FRAM

In the next article I will show you the details of using the FreeRTOS FAT SL filesystem.

Build the FreeRTOS Template & Schematic

I start the project from my FreeRTOS template project.  You can read all about that here.  Then I add in the components required to make things work.  The schematic is simple:

  • A UART component to run the Command Line Interpreter
  • An I2C to control the FRAM

FreeRTOS FAT SL Example Schematic

The I2C is setup as a master at it highest speed setting.

FreeRTOS FAT SL I2C Configuration

On the CY8CKIT-044 the pins need to be configured as so:

FreeRTOS FAT SL - Pin Configuration

Import the FreeRTOS FAT SL FileSystem & FRAM Media Driver

The first step in importing the FreeRTOS FAT SL FileSystem and and media driver is to copy the FreeRTOS-Plus-FAT-SL directory into my project.  Once that is done, my folder structure looks like this:

FreeRTOS FAT SL Code Layout

The next step is to fix the include paths to include the config, api and psp include directories.  This can be done on the build settings menu.

FreeRTOS FAT SL Include Files

Finally I import the .h and .c files into my project so that it looks like this:

FreeRTOS FAT SL Project Directory Structure

Build a Command Line Interpreter (CLI)

I think that it is convenient to have a command line utility (one that connects to the UART port) to send commands to my program to test it.  To build the CLI, I create a task called uartTask which takes keys from the terminal and then processes them in a giant switch statement.  While I was building the FreeRTOS FAT SL system, I noticed that FreeRTOS also has a scheme for CLIs which I will try out in the future.

In the UART configuration I turn on the “RX FIFO not empty” interrupt (meaning that there is data in the fifo that needs to be processed)

FreeRTOS FAT SL UART Configuration

I connect the interrupt to the interrupt service routine on line 64.  In the ISR I use the FreeRTOS notification scheme to send notifications to the uartTask to wakeup and process data (line 50).

My CLI has two different things that it does:

  • It calls functions in the file extestfs.c that start with “ex” , meaning example, to format, initalize etc.
  • It keeps a “currentSector” variable that lets me print out the raw data in a sector.  The currentSector variable is incremented (with the keyboard +) and decremented (with the keyboard -) and set to 0 with the (keyboard 0)

Once all of the keys have been processed (the Rx FIFO buffer is empty – line 71), it turns back on the Rx FIFO interrupt (lines 150-151), then waits for another notification from the ISR (line 69)

TaskHandle_t uartTaskHandle;
void uartISR()
{
BaseType_t xHigherPriorityTaskWoken;
// disable the interrupt
UART_SetRxInterruptMode(0);
vTaskNotifyGiveFromISR(uartTaskHandle,&xHigherPriorityTaskWoken);
portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
}
// This is the main task which processes commands from the UART and prints the results
// on the screen.
void uartTask(void *arg)
{
(void)arg;
UART_Start();
I2C_Start();
clearScreen();
UART_UartPutString("Start Filesystem Demo\n");
UART_SetCustomInterruptHandler(uartISR);
int currentSector=0;    
while(1)
{
ulTaskNotifyTake(pdTRUE,portMAX_DELAY);
while(UART_SpiUartGetRxBufferSize()) // if there is data then read and process
{
char c;
c= UART_UartGetChar();
switch(c)
{
case 'i': // Initialize the RTOS
exInit();
break;
case 'f': // Format the FRAM
exFormat();
break;
case 'q': // Return the drive information
exDriveInfo();
break;
case 'w': // Create a file
exCreateFile();
break;
case 'r': // Read the file that was created (if it exists)
exReadFile();
break;
case '0': // Goto to sector 0 and print the data
currentSector = 0;
exPrintSector(0,0,0);
break;
case '+': // Print the "current" sector and go to the next
exPrintSector(0,0,currentSector);
currentSector += 1;
break;
case '-': // print the current sector and go to the previous
exPrintSector(0,0,currentSector);
currentSector -= 1;
if(currentSector<0)
currentSector =0;
break;
case 'd': // Do a directory
exDirectory();
break;
case 'c':
clearScreen();
break;
case 'b': // Erase the FRAM (write all 0's)
blankFRAM();
break;
case '?': // Print out the list of commands
UART_UartPutString("b - Blank FRAM - write all 0's\n");
UART_UartPutString("i - Initalize Filesystem\n");
UART_UartPutString("f - Format FRAM\n");
UART_UartPutString("q - Print FileSystem Information\n");
UART_UartPutString("w - Create a file called \"afile.bin\"\n");
UART_UartPutString("r - Read the file called \"afile.bin\" and print contents\n");
UART_UartPutString("0 - Goto sector 0 and print contents\n");
UART_UartPutString("+ - Goto next sector and print contents\n");
UART_UartPutString("- - Goto previous sector and print contents\n");
UART_UartPutString("d - Print Directory\n");
UART_UartPutString("c - Clear Screen\n");
UART_UartPutString("? - Print help\n");        
break;
default:
UART_UartPutString("Unknown :");
UART_UartPutChar(c);
UART_UartPutChar('\n');
break;
}
}
// Turn the interrupts back on
UART_ClearRxInterruptSource(UART_INTR_RX_NOT_EMPTY); 
UART_SetRxInterruptMode(UART_INTR_RX_NOT_EMPTY);
}
}

Nuke the FRAM Data

I thought that it would be a good idea to have a function to put 0’s in all of the locations in the FRAM, to prove that I could start with a clean slate.  This function does just that.  Specifically it write 0’s to the 64K locations in I2C address 0x50 (the first bank) and to I2C address 0x51 (the second bank)

// This function erases - write 0's into the FRAM... also known as NUKE the FRAM
void blankFRAM(void)
{
int i;
UART_UartPutString("Starting Erase 1st Block\n");
I2C_I2CMasterSendStart(0x50,I2C_I2C_WRITE_XFER_MODE);
I2C_I2CMasterWriteByte(0);
I2C_I2CMasterWriteByte(0);
for(i=0;i<0xFFFF;i++) // Write 64K of 0's to erase first bank
{
I2C_I2CMasterWriteByte(0);
}
I2C_I2CMasterSendStop();
UART_UartPutString("Starting Erase 2nd Block\n");
I2C_I2CMasterSendStart(0x51,I2C_I2C_WRITE_XFER_MODE);
I2C_I2CMasterWriteByte(0);
I2C_I2CMasterWriteByte(0);
for(i=0;i<0xFFFF;i++) // write 64k of 0's to erase 2nd bank
{
I2C_I2CMasterWriteByte(0);
}
I2C_I2CMasterSendStop();
UART_UartPutString("Erase Complete\n");
}

As always you can find this project on the IoT Expert GitHub site git@github.com:iotexpert/PSoC-FileSystem.git

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