1 /* mbed Microcontroller Library
2 * Copyright (c) 2006-2013 ARM Limited
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
16 // math.h required for floating point operations for baud rate calculation
21 #include "serial_api.h"
24 #include "PeripheralPins.h" // For the Peripheral to Pin Definitions found in the individual Target's Platform
26 /******************************************************************************
28 ******************************************************************************/
31 static uint32_t serial_irq_ids[UART_NUM] = {0};
32 static uart_irq_handler irq_handler;
34 int stdio_uart_inited = 0;
37 void serial_init(serial_t *obj, PinName tx, PinName rx) {
38 int is_stdio_uart = 0;
40 // determine the UART to use
41 UARTName uart_tx = (UARTName)pinmap_peripheral(tx, PinMap_UART_TX);
42 UARTName uart_rx = (UARTName)pinmap_peripheral(rx, PinMap_UART_RX);
43 UARTName uart = (UARTName)pinmap_merge(uart_tx, uart_rx);
44 MBED_ASSERT((int)uart != NC);
46 obj->uart = (LPC_USART_Type *)uart;
47 LPC_SYSCON->SYSAHBCLKCTRL |= (1<<12);
49 // [TODO] Consider more elegant approach
50 // disconnect USBTX/RX mapping mux, for case when switching ports
52 pin_function(USBTX, 0);
53 pin_function(USBRX, 0);
56 // enable fifos and default rx trigger level
57 obj->uart->FCR = 1 << 0 // FIFO Enable - 0 = Disables, 1 = Enabled
58 | 0 << 1 // Rx Fifo Reset
59 | 0 << 2 // Tx Fifo Reset
60 | 0 << 6; // Rx irq trigger level - 0 = 1 char, 1 = 4 chars, 2 = 8 chars, 3 = 14 chars
63 obj->uart->IER = 0 << 0 // Rx Data available irq enable
64 | 0 << 1 // Tx Fifo empty irq enable
65 | 0 << 2; // Rx Line Status irq enable
67 // set default baud rate and format
68 serial_baud (obj, 9600);
69 serial_format(obj, 8, ParityNone, 1);
71 // pinout the chosen uart
72 pinmap_pinout(tx, PinMap_UART_TX);
73 pinmap_pinout(rx, PinMap_UART_RX);
75 // set rx/tx pins in PullUp mode
84 case UART_0: obj->index = 0; break;
87 is_stdio_uart = (uart == STDIO_UART) ? (1) : (0);
90 stdio_uart_inited = 1;
91 memcpy(&stdio_uart, obj, sizeof(serial_t));
95 void serial_free(serial_t *obj) {
96 serial_irq_ids[obj->index] = 0;
100 // set the baud rate, taking in to account the current SystemFrequency
101 void serial_baud(serial_t *obj, int baudrate) {
102 LPC_SYSCON->UARTCLKDIV = 0x1;
103 uint32_t PCLK = SystemCoreClock;
104 // First we check to see if the basic divide with no DivAddVal/MulVal
105 // ratio gives us an integer result. If it does, we set DivAddVal = 0,
106 // MulVal = 1. Otherwise, we search the valid ratio value range to find
107 // the closest match. This could be more elegant, using search methods
108 // and/or lookup tables, but the brute force method is not that much
109 // slower, and is more maintainable.
110 uint16_t DL = PCLK / (16 * baudrate);
112 uint8_t DivAddVal = 0;
117 if ((PCLK % (16 * baudrate)) != 0) { // Checking for zero remainder
118 int err_best = baudrate, b;
119 for (mv = 1; mv < 16 && !hit; mv++)
121 for (dav = 0; dav < mv; dav++)
123 // baudrate = PCLK / (16 * dlv * (1 + (DivAdd / Mul))
124 // solving for dlv, we get dlv = mul * PCLK / (16 * baudrate * (divadd + mul))
125 // mul has 4 bits, PCLK has 27 so we have 1 bit headroom which can be used for rounding
126 // for many values of mul and PCLK we have 2 or more bits of headroom which can be used to improve precision
127 // note: X / 32 doesn't round correctly. Instead, we use ((X / 16) + 1) / 2 for correct rounding
129 if ((mv * PCLK * 2) & 0x80000000) // 1 bit headroom
130 dlv = ((((2 * mv * PCLK) / (baudrate * (dav + mv))) / 16) + 1) / 2;
131 else // 2 bits headroom, use more precision
132 dlv = ((((4 * mv * PCLK) / (baudrate * (dav + mv))) / 32) + 1) / 2;
134 // datasheet says if DLL==DLM==0, then 1 is used instead since divide by zero is ungood
138 // datasheet says if dav > 0 then DL must be >= 2
139 if ((dav > 0) && (dlv < 2))
142 // integer rearrangement of the baudrate equation (with rounding)
143 b = ((PCLK * mv / (dlv * (dav + mv) * 8)) + 1) / 2;
145 // check to see how we went
146 b = abs(b - baudrate);
165 // set LCR[DLAB] to enable writing to divider registers
166 obj->uart->LCR |= (1 << 7);
168 // set divider values
169 obj->uart->DLM = (DL >> 8) & 0xFF;
170 obj->uart->DLL = (DL >> 0) & 0xFF;
171 obj->uart->FDR = (uint32_t) DivAddVal << 0
172 | (uint32_t) MulVal << 4;
175 obj->uart->LCR &= ~(1 << 7);
178 void serial_format(serial_t *obj, int data_bits, SerialParity parity, int stop_bits) {
179 MBED_ASSERT((stop_bits == 1) || (stop_bits == 2)); // 0: 1 stop bits, 1: 2 stop bits
180 MBED_ASSERT((data_bits > 4) && (data_bits < 9)); // 0: 5 data bits ... 3: 8 data bits
181 MBED_ASSERT((parity == ParityNone) || (parity == ParityOdd) || (parity == ParityEven) ||
182 (parity == ParityForced1) || (parity == ParityForced0));
187 int parity_enable = 0, parity_select = 0;
189 case ParityNone: parity_enable = 0; parity_select = 0; break;
190 case ParityOdd : parity_enable = 1; parity_select = 0; break;
191 case ParityEven: parity_enable = 1; parity_select = 1; break;
192 case ParityForced1: parity_enable = 1; parity_select = 2; break;
193 case ParityForced0: parity_enable = 1; parity_select = 3; break;
198 obj->uart->LCR = data_bits << 0
201 | parity_select << 4;
204 /******************************************************************************
205 * INTERRUPTS HANDLING
206 ******************************************************************************/
207 static inline void uart_irq(uint32_t iir, uint32_t index) {
208 // [Chapter 14] LPC17xx UART0/2/3: UARTn Interrupt Handling
211 case 1: irq_type = TxIrq; break;
212 case 2: irq_type = RxIrq; break;
216 if (serial_irq_ids[index] != 0)
217 irq_handler(serial_irq_ids[index], irq_type);
220 void uart0_irq() {uart_irq((LPC_USART->IIR >> 1) & 0x7, 0);}
222 void serial_irq_handler(serial_t *obj, uart_irq_handler handler, uint32_t id) {
223 irq_handler = handler;
224 serial_irq_ids[obj->index] = id;
227 void serial_irq_set(serial_t *obj, SerialIrq irq, uint32_t enable) {
228 IRQn_Type irq_n = (IRQn_Type)0;
230 switch ((int)obj->uart) {
231 case UART_0: irq_n=UART_IRQn ; vector = (uint32_t)&uart0_irq; break;
235 obj->uart->IER |= 1 << irq;
236 NVIC_SetVector(irq_n, vector);
237 NVIC_EnableIRQ(irq_n);
239 int all_disabled = 0;
240 SerialIrq other_irq = (irq == RxIrq) ? (TxIrq) : (RxIrq);
242 obj->uart->IER &= ~(1 << irq);
243 all_disabled = (obj->uart->IER & (1 << other_irq)) == 0;
246 NVIC_DisableIRQ(irq_n);
250 /******************************************************************************
252 ******************************************************************************/
253 int serial_getc(serial_t *obj) {
254 while (!serial_readable(obj));
255 return obj->uart->RBR;
258 void serial_putc(serial_t *obj, int c) {
259 while (!serial_writable(obj));
263 int serial_readable(serial_t *obj) {
264 return obj->uart->LSR & 0x01;
267 int serial_writable(serial_t *obj) {
268 return obj->uart->LSR & 0x20;
271 void serial_clear(serial_t *obj) {
272 obj->uart->FCR = 1 << 1 // rx FIFO reset
273 | 1 << 2 // tx FIFO reset
274 | 0 << 6; // interrupt depth
277 void serial_pinout_tx(PinName tx) {
278 pinmap_pinout(tx, PinMap_UART_TX);
281 void serial_break_set(serial_t *obj) {
282 obj->uart->LCR |= (1 << 6);
285 void serial_break_clear(serial_t *obj) {
286 obj->uart->LCR &= ~(1 << 6);