Diff: targets/TARGET_NXP/TARGET_LPC13XX/serial_api.c

Revision:

0:f269e3021894

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NXP/TARGET_LPC13XX/serial_api.c	Sun Oct 23 15:10:02 2016 +0000
@@ -0,0 +1,300 @@
+/* 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
+#include "mbed_assert.h"
+#include <math.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "serial_api.h"
+#include "cmsis.h"
+#include "pinmap.h"
+
+/******************************************************************************
+ * INITIALIZATION
+ ******************************************************************************/
+#define UART_NUM    1
+
+static const PinMap PinMap_UART_TX[] = {
+    {P0_19, UART_0, 1},
+    {P1_13, UART_0, 3},
+    {P1_27, UART_0, 2},
+    { NC  , NC    , 0}
+};
+
+static const PinMap PinMap_UART_RX[] = {
+    {P0_18, UART_0, 1},
+    {P1_14, UART_0, 3},
+    {P1_26, UART_0, 2},
+    {NC   , NC    , 0}
+};
+
+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 serial_init(serial_t *obj, PinName tx, PinName rx) {
+    int is_stdio_uart = 0;
+    
+    // determine the UART to use
+    UARTName uart_tx = (UARTName)pinmap_peripheral(tx, PinMap_UART_TX);
+    UARTName uart_rx = (UARTName)pinmap_peripheral(rx, PinMap_UART_RX);
+    UARTName uart = (UARTName)pinmap_merge(uart_tx, uart_rx);
+    MBED_ASSERT((int)uart != NC);
+    
+    obj->uart = (LPC_USART_Type *)uart;
+    LPC_SYSCON->SYSAHBCLKCTRL |= (1<<12);
+    
+    // [TODO] Consider more elegant approach
+    // disconnect USBTX/RX mapping mux, for case when switching ports
+    //pin_function(USBTX, 0);
+    //pin_function(USBRX, 0);
+    
+    // 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
+    serial_baud  (obj, 9600);
+    serial_format(obj, 8, ParityNone, 1);
+    
+    // pinout the chosen uart
+    pinmap_pinout(tx, PinMap_UART_TX);
+    pinmap_pinout(rx, PinMap_UART_RX);
+    
+    // set rx/tx pins in PullUp mode
+    if (tx != NC) {
+        pin_mode(tx, PullUp);
+    }
+    if (rx != NC) {
+        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 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 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 serial_format(serial_t *obj, int data_bits, SerialParity parity, int stop_bits) {
+    MBED_ASSERT((stop_bits == 1) || (stop_bits == 2)); // 0: 1 stop bits, 1: 2 stop bits
+    MBED_ASSERT((data_bits > 4) && (data_bits < 9)); // 0: 5 data bits ... 3: 8 data bits
+    MBED_ASSERT((parity == ParityNone) || (parity == ParityOdd) || (parity == ParityEven) ||
+           (parity == ParityForced1) || (parity == ParityForced0));
+
+    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 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 uart0_irq() {uart_irq((LPC_USART->IIR >> 1) & 0x7, 0);}
+
+void serial_irq_handler(serial_t *obj, uart_irq_handler handler, uint32_t id) {
+    irq_handler = handler;
+    serial_irq_ids[obj->index] = id;
+}
+
+void 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=USART_IRQn ; vector = (uint32_t)&uart0_irq; break;
+    }
+    
+    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 serial_getc(serial_t *obj) {
+    while (!serial_readable(obj));
+    return obj->uart->RBR;
+}
+
+void serial_putc(serial_t *obj, int c) {
+    while (!serial_writable(obj));
+    obj->uart->THR = c;
+}
+
+int serial_readable(serial_t *obj) {
+    return obj->uart->LSR & 0x01;
+}
+
+int serial_writable(serial_t *obj) {
+    return obj->uart->LSR & 0x20;
+}
+
+void serial_clear(serial_t *obj) {
+    obj->uart->FCR = 1 << 1  // rx FIFO reset
+                   | 1 << 2  // tx FIFO reset
+                   | 0 << 6; // interrupt depth
+}
+
+void serial_pinout_tx(PinName tx) {
+    pinmap_pinout(tx, PinMap_UART_TX);
+}
+
+void serial_break_set(serial_t *obj) {
+    obj->uart->LCR |= (1 << 6);
+}
+
+void serial_break_clear(serial_t *obj) {
+    obj->uart->LCR &= ~(1 << 6);
+}
+