Jason Garner / registers

my implementation of mbed-like classes using the LPC1768 register access.

Dependents:   registers-example RedWireBridge

This is just to satisfy my curiosity on how the mbed libraries work. I put it here just in case others are too. Every time I learn how another internal register works, I'll keep it here to save myself from future coding headaches.

working

• DigitalIn
• DigitalOut
• wait()

mostly working

• Serial
• Timer
• Ticker
• Timeout

Serial doesn't have all the methods that mbed had, but it works for me. (only UART0, so only over USB to the pc for now) Timer has the same limitations of mbed for default resolution (30 min limit), and if you start at the end of resolution and stop after it rolls back to 0, it doesn't take that into account. But I added the option to change resolution, so I can have longer timers.

For Ticker, I used a 100 microsecond timer instead of a 1 microsecond Timer, so the smallest interval in between function calls is 100 microseconds. (10KHz) However, this means that the maximum interval in between function calls is 59 hours. (untested)

The Timeout class, simply uses a Ticker, but then marks it as nonactive after the first function call. Automatically calls the detach() function when attaching it again, so no don't need to worry about it.

//this file is for all the global functions that I need to use
//but are here, so they are not cluttering up main.cpp
#include "functions.h"

//this uses Timer 0, but we could just as easily change it to Timer 1, 2 or 3
void wait(float time) //seconds
{
    uint32_t us = time * 1000000; //microseconds

    uint8_t pclk;
    uint32_t pclkdiv = (LPC_SC->PCLKSEL0 >> 2) & 0x03;

    switch ( pclkdiv ) // table 42 (page 57 in user manual)
    {
      case 0x00:
      default:
            pclk = 4;
            break;
      case 0x01:
            pclk = 1;
            break;
      case 0x02:
            pclk = 2;
            break;
      case 0x03:
            pclk = 8;
            break;
    }

    LPC_TIM0->TCR = 0x02;           /* reset timer */
    LPC_TIM0->PR  = (SystemCoreClock / (pclk * 1000000));
    LPC_TIM0->MR0 = us;             /* enter delay time */
    LPC_TIM0->IR  = 0xff;           /* reset all interrrupts */
    LPC_TIM0->MCR = 0x04;           /* stop timer on match */
    LPC_TIM0->TCR = 0x01;           /* start timer */

    /* wait until delay time has elapsed */
    while (LPC_TIM0->TCR & 0x01);
}