main.c

software LCD driver for microcontroller

/*=============================================================================
Cyan Technology Limited

FILE - main.c

DESCRIPTION
    Demonstrates direct drive software for a static LCD. Parallel and general
	purpose IOs are initialised to drive a 4-digit 7-segment display, with
	support for one backplane. The PIOs are updated at 64 Hz using timer
	interrupt to generate a 32 Hz LCD frame rate. An elapsed minute/second
	time counter, driven by a 1 Hz counter interrupt is used as a LCD
	application example.

MODIFICATION DETAILS
=============================================================================*/


/******************************************************************************
Project level include files.
******************************************************************************/

#include <ecog.h>
#include <ecog1.h>
#include <stdio.h>
#include "driver_lib.h"

 
/******************************************************************************
Include files for public interfaces from other modules.
******************************************************************************/


/******************************************************************************
Declaration of public functions.
******************************************************************************/


/******************************************************************************
Private constants and types.
******************************************************************************/

#define BP_HIGH		0x10					// To drive backplane (GPIO17) high
#define BP_LOW		0x20					// To drive backplane (GPIO17) low


/******************************************************************************
Declaration of static functions.
******************************************************************************/

// Called from irq service routines
void __irq_entry cnt1_handler (void);		// Update elapsed time counter
void __irq_entry tmr_handler (void);		// Drive LCD


/******************************************************************************
Global variables.
******************************************************************************/


/******************************************************************************
Module global variables.
******************************************************************************/

// Elapsed minute/sec time counter current value
static int clk_sec_lower = 0;
static int clk_sec_upper = 0;
static int clk_min_lower = 0;
static int clk_min_upper = 0;


/******************************************************************************
Definition of API functions.
******************************************************************************/


/******************************************************************************
NAME
    main

SYNOPSIS
    int main(int argc, char * argv[])

FUNCTION
    Initialse the system and then go into sleep mode.

RETURNS
    Exit code.
******************************************************************************/

int main(int argc, char* argv[])
{
    // Select low frequency clock sources as timers clock source in configurator 
	
	/* Initialise timer to generate a 64 Hz interrupt. Clock source is
	 * the 32 kHz reference which is further divide down by 2^8 and 2.
	 */
	fd.ssm.rst_clr.tmr = 1;
	fd.ssm.div_sel.tmr = 0;
    fd.ssm.tap_sel3.tmr = 6;
	fd.ssm.clk_en.tmr = 1;
	
	rg.tim.tmr_ld = 1;
    fd.tim.cmd.tmr_ld = 1;
    fd.tim.ctrl_en.tmr_auto_re_ld = 1;
    fd.tim.ctrl_en.tmr_cnt = 1;
	fd.tim.int_en1.tmr_exp = 1;
    
	/* Initialise counter 1 to generate a 1 Hz interrupt in configurator.
	 * Clock source is the 32 kHz reference which is further divide down
	 * by 2^13 and 4.
	 */
	
	// Start counter 1 and enable interrupt
    rg.tim.ctrl_en = TIM_CTRL_EN_CNT1_CNT_MASK;
	rg.tim.int_en1 = TIM_INT_EN1_CNT1_EXP_MASK;
	
    /* Initialise PIOs as driven outputs in configurator:
	 * Port L as PIOB 08-15 to drive LCD digit 1
	 * Port K as PIOB 00-07 to drive LCD digit 2
	 * Port F as PIOA 08-15 to drive LCD digit 3
	 * Port E as PIOA 00-07 to drive LCD digit 4
	 */
	
	// Initialise Port I I2 to use GPIO17 for backplane output in configurator
	
	// Disable unused peripheral clocks during sleep, and on wakeup in configurator
	
    // Set CPU clock to 16 kHz in configurator
    
	// Disable high ref oscillator and high pll to save power in configurator
    rg.ssm.clk_dis = SSM_CLK_DIS_HIGH_OSC_MASK | SSM_CLK_DIS_HIGH_PLL_MASK;
	
    sleep();								// Put processor to sleep
	
	//while(1);
	
    return 0;
}


/******************************************************************************
Definition of Static Functions.
******************************************************************************/


/******************************************************************************
NAME
    cnt1_handler

SYNOPSIS
    void __irq_entry cnt1_handler(void)

FUNCTION
    Interrupt handler for counter 1 interrupt. Wakes up the processor every
	1 second to increment the elapsed minute/second time counter.

RETURNS
    Nothing.
******************************************************************************/

void __irq_entry cnt1_handler (void)
{    
    fd.tim.int_clr1.cnt1_exp = 1;           // Clear the interrupt
    
	// Increment the elapsed time counter
	clk_sec_lower++;
	if (10 == clk_sec_lower)
	{
		clk_sec_lower = 0;
		clk_sec_upper++;
		if (6 == clk_sec_upper)
		{
			clk_sec_upper = 0;
			clk_min_lower++;
			if (10 == clk_min_lower)
			{
				clk_min_lower = 0;
				clk_min_upper++;
				if (6 == clk_min_upper)
				{
					clk_min_upper = 0;
				}
			}
		}
	}
}


/******************************************************************************
NAME
    tmr_handler

SYNOPSIS
    void __irq_entry tmr_handler(void)

FUNCTION
    Interrupt handler for timer interrupt. Responsible for driving the LCD
	segments via the PIOs and backplane via GPIO17. Initialised to run at
	64 Hz to generate a 32 Hz LCD frame rate.

RETURNS
    Nothing.
******************************************************************************/

void __irq_entry tmr_handler (void)
{
    static int pao, pbo;               		// Digit displays buffer
	static int bp_sig;						// Backplane signal polarity

	// Coded digit display
	static int disp_clk_sec_lower;
	static int disp_clk_sec_upper;
	static int disp_clk_min_lower;
	static int disp_clk_min_upper;
	
	// 7-segment coded data for the number 0 to 9
    const int seg_code[] = { 0x3f, 0x06, 0x5b, 0x4f, 0x66, 
							 0x6d, 0x7d, 0x07, 0x7f, 0x67};
    
    fd.tim.int_clr1.tmr_exp = 1;            // Clear the interrupt
	
	// Update the LCD display
    rg.io.pa_out = pao;
    rg.io.pb_out = pbo;
	rg.io.gp16_19_out = bp_sig;
	
    // Encode the next elapsed time counter value
    disp_clk_sec_lower = seg_code[clk_sec_lower];
	disp_clk_sec_upper = seg_code[clk_sec_upper];
	disp_clk_min_lower = seg_code[clk_min_lower];
	disp_clk_min_upper = seg_code[clk_min_upper];
	disp_clk_min_upper += 0x80;				// Add colon
	
	// Generate the next half of a LCD frame value
    if (bp_sig == BP_HIGH)
    {
        bp_sig = BP_LOW;    				// Invert backplane for next update
    }
    else
    {
        bp_sig = BP_HIGH;    				// Invert backplane for next update
        disp_clk_sec_lower ^= 0xff;			// Invert bits
		disp_clk_sec_upper ^= 0xff;
		disp_clk_min_lower ^= 0xff;
		disp_clk_min_upper ^= 0xff;
	}
	
	// Fill the digit display buffers, ready for next update.
	pao = (disp_clk_sec_upper << 8) + disp_clk_sec_lower;
    pbo = (disp_clk_min_upper << 8) + disp_clk_min_lower;
}