Arduino Uno with a 32-bit ARM Cortex-M0 in 28 pin DIL package

Using Arduino Microcontrollers
26

I have not studied it too much but the LPC Xpresso IDE, designed for ARMs produced by NXP, seems quite easy to work with.

The IDE hides the internal registers and you work mainly with easy to understand functions that set timers, IO ports, etc..
However, there may be traps, complications. LPC Xpresso IDE does not have a simulator, for instance, like Keil. You need the real hardware to test your code.

LPC Xpresso code example:

/****************************************************************************
 *   $Id:: PWM16_32test.c 3635 2010-06-02 00:31:46Z usb00423                $
 *   Project: NXP LPC11xx 16-bit/32-bit PWM example
 *
 *   Description:
 *     This file contains PWM test modules, main entry, to test PWM APIs.
 *
 ****************************************************************************
 * Software that is described herein is for illustrative purposes only
 * which provides customers with programming information regarding the
 * products. This software is supplied "AS IS" without any warranties.
 * NXP Semiconductors assumes no responsibility or liability for the
 * use of the software, conveys no license or title under any patent,
 * copyright, or mask work right to the product. NXP Semiconductors
 * reserves the right to make changes in the software without
 * notification. NXP Semiconductors also make no representation or
 * warranty that such application will be suitable for the specified
 * use without further testing or modification.
****************************************************************************/

#include "driver_config.h"
#include "target_config.h"

#include "timer32.h"
#include "timer16.h"
#include "gpio.h"

extern volatile uint32_t timer32_0_counter;

volatile uint32_t period = 1000;  //48Khz PWM frequency

/* Main Program */

int main (void) {
	/* Initialize 32-bits timer 0 */
	init_timer32(0, TIME_INTERVAL);
	enable_timer32(0);
	
	/* Initialize the PWM in timer32_1 enabling match0 output */
	init_timer32PWM(1, period, MATCH0);
	setMatch_timer32PWM (1, 0, period/4);
	enable_timer32(1);

	/* Initialize the PWM in timer16_1 enabling match1 output */
	init_timer16PWM(1, period, MATCH1, 0);
	setMatch_timer16PWM (1, 1, period/8);
	enable_timer16(1);

	/* Enable AHB clock to the GPIO domain. */
	LPC_SYSCON->SYSAHBCLKCTRL |= (1<<6);
	
	/* Set port 2_0 to output */
	GPIOSetDir( 2, 0, 1 );
	
	while (1)                                /* Loop forever */
	{
		/* I/O configuration and LED setting pending. */
		if ( (timer32_0_counter > 0) && (timer32_0_counter <= 50) )
		{
			GPIOSetValue( 2, 0, 0 );
		}
		if ( (timer32_0_counter > 50) && (timer32_0_counter <= 100) )
		{
			GPIOSetValue( 2, 0, 1 );
		}
		else 
			while ( timer32_0_counter < 100 ); //wait for 
	  	timer32_0_counter = 0;
	}
}

A nice feature I like is that LPC Xpresso displays explanations about a function, ex. init_timer32 (the meaning of parameters, etc.) if you glide the mouse cursor over its name.