Teacup_Firmware/mbed-serial_api.c

/* mbed Microcontroller Library
 * Copyright (c) 2006-2013 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
// math.h required for floating point operations for baud rate calculation
/*
  Notes for Teacup:

  Copied from $(MBED)/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/serial_api.c.

  Used only to get things running quickly. Without serial it's almost
  impossible to see wether code changes work. Should go away soon, because
  all this MBED stuff is too bloated for Teacup's purposes.

  - Prefixed names of #include files with mbed- to match the names of the
    copies in the Teacup repo.
  - Wrapped the whole file in #ifdef __ARMEL__ to not cause conflicts with
    AVR builds.
  - Prefixed function names with mbed_ to not conflict with Teacup names.
  - Fixed mbed_uart0_irq() function prototype.
*/
#ifdef __ARM_LPC1114__
#include "mbed-mbed_assert.h"
#include <math.h>
#include <string.h>
#include <stdlib.h>

#include "mbed-serial_api.h"
#include "mbed-cmsis.h"
#include "mbed-pinmap.h"

/******************************************************************************
 * INITIALIZATION
 ******************************************************************************/
#define UART_NUM    1

static uint32_t serial_irq_ids[UART_NUM] = {0};
static uart_irq_handler irq_handler;

int stdio_uart_inited = 0;
serial_t stdio_uart;

void mbed_serial_init(serial_t *obj, PinName tx, PinName rx) {
    int is_stdio_uart = 0;
    
    UARTName uart = UART_0;
    
    obj->uart = (LPC_UART_TypeDef *)uart;
    LPC_SYSCON->SYSAHBCLKCTRL |= (1<<12);
    
    // enable fifos and default rx trigger level
    obj->uart->FCR = 1 << 0  // FIFO Enable - 0 = Disables, 1 = Enabled
                   | 0 << 1  // Rx Fifo Reset
                   | 0 << 2  // Tx Fifo Reset
                   | 0 << 6; // Rx irq trigger level - 0 = 1 char, 1 = 4 chars, 2 = 8 chars, 3 = 14 chars
    
    // disable irqs
    obj->uart->IER = 0 << 0  // Rx Data available irq enable
                   | 0 << 1  // Tx Fifo empty irq enable
                   | 0 << 2; // Rx Line Status irq enable
    
    // set default baud rate and format
    mbed_serial_baud  (obj, 9600);
    mbed_serial_format(obj, 8, ParityNone, 1);
    
    // pinout the chosen uart
    pin_function(tx, 0x01);
    pin_mode(tx, PullUp);
    pin_function(rx, 0x01);
    pin_mode(rx, PullUp);

    switch (uart) {
        case UART_0: obj->index = 0; break;
    }
    
    is_stdio_uart = (uart == STDIO_UART) ? (1) : (0);
    
    if (is_stdio_uart) {
        stdio_uart_inited = 1;
        memcpy(&stdio_uart, obj, sizeof(serial_t));
    }
}

void mbed_serial_free(serial_t *obj) {
    serial_irq_ids[obj->index] = 0;
}

// serial_baud
// set the baud rate, taking in to account the current SystemFrequency
void mbed_serial_baud(serial_t *obj, int baudrate) {
    LPC_SYSCON->UARTCLKDIV = 0x1;
    uint32_t PCLK = SystemCoreClock;
    // First we check to see if the basic divide with no DivAddVal/MulVal
    // ratio gives us an integer result. If it does, we set DivAddVal = 0,
    // MulVal = 1. Otherwise, we search the valid ratio value range to find
    // the closest match. This could be more elegant, using search methods
    // and/or lookup tables, but the brute force method is not that much
    // slower, and is more maintainable.
    uint16_t DL = PCLK / (16 * baudrate);
    
    uint8_t DivAddVal = 0;
    uint8_t MulVal = 1;
    int hit = 0;
    uint16_t dlv;
    uint8_t mv, dav;
    if ((PCLK % (16 * baudrate)) != 0) {     // Checking for zero remainder
        int err_best = baudrate, b;
        for (mv = 1; mv < 16 && !hit; mv++)
        {
            for (dav = 0; dav < mv; dav++)
            {
                // baudrate = PCLK / (16 * dlv * (1 + (DivAdd / Mul))
                // solving for dlv, we get dlv = mul * PCLK / (16 * baudrate * (divadd + mul))
                // mul has 4 bits, PCLK has 27 so we have 1 bit headroom which can be used for rounding
                // for many values of mul and PCLK we have 2 or more bits of headroom which can be used to improve precision
                // note: X / 32 doesn't round correctly. Instead, we use ((X / 16) + 1) / 2 for correct rounding

                if ((mv * PCLK * 2) & 0x80000000) // 1 bit headroom
                    dlv = ((((2 * mv * PCLK) / (baudrate * (dav + mv))) / 16) + 1) / 2;
                else // 2 bits headroom, use more precision
                    dlv = ((((4 * mv * PCLK) / (baudrate * (dav + mv))) / 32) + 1) / 2;

                // datasheet says if DLL==DLM==0, then 1 is used instead since divide by zero is ungood
                if (dlv == 0)
                    dlv = 1;

                // datasheet says if dav > 0 then DL must be >= 2
                if ((dav > 0) && (dlv < 2))
                    dlv = 2;

                // integer rearrangement of the baudrate equation (with rounding)
                b = ((PCLK * mv / (dlv * (dav + mv) * 8)) + 1) / 2;

                // check to see how we went
                b = abs(b - baudrate);
                if (b < err_best)
                {
                    err_best  = b;

                    DL        = dlv;
                    MulVal    = mv;
                    DivAddVal = dav;

                    if (b == baudrate)
                    {
                        hit = 1;
                        break;
                    }
                }
            }
        }
    }
    
    // set LCR[DLAB] to enable writing to divider registers
    obj->uart->LCR |= (1 << 7);
    
    // set divider values
    obj->uart->DLM = (DL >> 8) & 0xFF;
    obj->uart->DLL = (DL >> 0) & 0xFF;
    obj->uart->FDR = (uint32_t) DivAddVal << 0
                   | (uint32_t) MulVal    << 4;
    
    // clear LCR[DLAB]
    obj->uart->LCR &= ~(1 << 7);
}

void mbed_serial_format(serial_t *obj, int data_bits, SerialParity parity, int stop_bits) {

    stop_bits -= 1;
    data_bits -= 5;

    int parity_enable, parity_select;
    switch (parity) {
        case ParityNone: parity_enable = 0; parity_select = 0; break;
        case ParityOdd : parity_enable = 1; parity_select = 0; break;
        case ParityEven: parity_enable = 1; parity_select = 1; break;
        case ParityForced1: parity_enable = 1; parity_select = 2; break;
        case ParityForced0: parity_enable = 1; parity_select = 3; break;
        default:
            break;
    }
    
    obj->uart->LCR = data_bits            << 0
                   | stop_bits            << 2
                   | parity_enable        << 3
                   | parity_select        << 4;
}

/******************************************************************************
 * INTERRUPTS HANDLING
 ******************************************************************************/
static inline void mbed_uart_irq(uint32_t iir, uint32_t index) {
    // [Chapter 14] LPC17xx UART0/2/3: UARTn Interrupt Handling
    SerialIrq irq_type;
    switch (iir) {
        case 1: irq_type = TxIrq; break;
        case 2: irq_type = RxIrq; break;
        default: return;
    }
    
    if (serial_irq_ids[index] != 0)
        irq_handler(serial_irq_ids[index], irq_type);
}

void mbed_uart0_irq(void) {mbed_uart_irq((LPC_UART->IIR >> 1) & 0x7, 0);}

void mbed_serial_irq_handler(serial_t *obj, uart_irq_handler handler, uint32_t id) {
    irq_handler = handler;
    serial_irq_ids[obj->index] = id;
}

void mbed_serial_irq_set(serial_t *obj, SerialIrq irq, uint32_t enable) {
    IRQn_Type irq_n = (IRQn_Type)0;
    uint32_t vector = 0;
    switch ((int)obj->uart) {
        case UART_0:
            irq_n=UART_IRQn;
            vector = (uint32_t)&mbed_uart0_irq;
            break;
        default:
            return;
    }
    
    if (enable) {
        obj->uart->IER |= 1 << irq;
        NVIC_SetVector(irq_n, vector);
        NVIC_EnableIRQ(irq_n);
    } else { // disable
        int all_disabled = 0;
        SerialIrq other_irq = (irq == RxIrq) ? (TxIrq) : (RxIrq);

        obj->uart->IER &= ~(1 << irq);
        all_disabled = (obj->uart->IER & (1 << other_irq)) == 0;
        
        if (all_disabled)
            NVIC_DisableIRQ(irq_n);
    }
}

/******************************************************************************
 * READ/WRITE
 ******************************************************************************/
int mbed_serial_getc(serial_t *obj) {
    while (!mbed_serial_readable(obj));
    return obj->uart->RBR;
}

void mbed_serial_putc(serial_t *obj, int c) {
    while (!mbed_serial_writable(obj));
    obj->uart->THR = c;
}

int mbed_serial_readable(serial_t *obj) {
    return obj->uart->LSR & 0x01;
}

int mbed_serial_writable(serial_t *obj) {
    return obj->uart->LSR & 0x20;
}

void mbed_serial_clear(serial_t *obj) {
    obj->uart->FCR = 1 << 1  // rx FIFO reset
                   | 1 << 2  // tx FIFO reset
                   | 0 << 6; // interrupt depth
}

void mbed_serial_break_clear(serial_t *obj) {
    obj->uart->LCR &= ~(1 << 6);
}

void mbed_serial_break_set(serial_t *obj) {
    obj->uart->LCR |= 1 << 6;
}
#endif /* __ARMEL__ */