include the mbed library with this snippet

/*  an attempt at PWM without using the mbed registers

*/

#define PINSEL4     (*(volatile unsigned char *)(0x4002C010))
#define PCONP       (*(volatile unsigned char *)(0x400FC0C4))
#define PCLKSEL0    (*(volatile unsigned char *)(0x400FC1A8))
#define PINSEL0     (*(volatile unsigned char *)(0x4002C000))
#define PINMODE4    (*(volatile unsigned char *)(0x4002C050))
#define PWM1MR0     (*(volatile unsigned char *)(0x40018018))
#define PWM1MCR     (*(volatile unsigned char *)(0x40018014))
#define PWM1TCR     (*(volatile unsigned char *)(0x40018004))
#define PWM1MR5     (*(volatile unsigned char *)(0x40018044))
#define PWM1PCR     (*(volatile unsigned char *)(0x4001804C))

int main(){
    
    while(1){

PCONP |= 1 << 6;        // power up PWM , powered up on reset, not requ
PCLKSEL0 |= 1 << 12;        // setting up the clock for pwm, clock = microcontroller clock i.e the prescaler value is 1.
PINSEL4 |= 1 << 6;      // p2.4 as PWM1 output
PINMODE4 |= 1 << 9;     // enable neither pull-up nor pull-down
PWM1MR0 = 16;   // PWM freq = PWM clock/16
PWM1MCR |= 1 << 1;      // reset timer on Match0
PWM1MR5 = 8;        // PWM duty cycle = 0.5


/*  8 is stored into MR5. therefore now one cycle of PWM waveform consists of 16PWM clock cycles
and for 8 of them the PWM output will be high and for remaining 8 cycles it will be low. 
therefore the effective signal produced is a waveform of frequency 
(PWM clock/6) with a duty cycle of 0.5
*/

PWM1TCR |= (1 << 0) | (1 << 3);     // enable timer/counter

/*
select control mode for each channel(except channel ) and enable the PWM output

*/

PWM1PCR |= 1 << 4; //configure channel 4 as double edge , refer to table 451 pg 519
//settiing bits 2-6 to 0 enables single edge 

PWM1PCR |= 1 << 12; //enable PWM for channel 4 output
PWM1PCR |= 1 << 13; // eanble PWM for channel 5 output , no need to configure channel 5 default is to 0 single side rise
    }
}