analogout_api.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2013 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include "analogout_api.h"
00017 
00018 #include "cmsis.h"
00019 #include "pinmap.h"
00020 #include "error.h"
00021 
00022 static const PinMap PinMap_DAC[] = {
00023     {P0_26, DAC_0, 2},
00024     {NC   , NC   , 0}
00025 };
00026 
00027 void analogout_init(dac_t *obj, PinName pin) {
00028     obj->dac = (DACName)pinmap_peripheral(pin, PinMap_DAC);
00029     if (obj->dac == (uint32_t)NC) {
00030         error("DAC pin mapping failed");
00031     }
00032     
00033     // power is on by default, set DAC clk divider is /4
00034     LPC_SC->PCLKSEL0 &= ~(0x3 << 22);
00035     
00036     // map out (must be done before accessing registers)
00037     pinmap_pinout(pin, PinMap_DAC);
00038     
00039     analogout_write_u16(obj, 0);
00040 }
00041 
00042 void analogout_free(dac_t *obj) {}
00043 
00044 static inline void dac_write(int value) {
00045     value &= 0x3FF; // 10-bit
00046     
00047     // Set the DAC output
00048     LPC_DAC->DACR = (0 << 16)       // bias = 0
00049                   | (value << 6);
00050 }
00051 
00052 static inline int dac_read() {
00053     return (LPC_DAC->DACR >> 6) & 0x3FF;
00054 }
00055 
00056 void analogout_write(dac_t *obj, float value) {
00057     if (value < 0.0f) {
00058         dac_write(0);
00059     } else if (value > 1.0f) {
00060         dac_write(0x3FF);
00061     } else {
00062         dac_write(value * (float)0x3FF);
00063     }
00064 }
00065 
00066 void analogout_write_u16(dac_t *obj, uint16_t value) {
00067     dac_write(value >> 6); // 10-bit
00068 }
00069 
00070 float analogout_read(dac_t *obj) {
00071     uint32_t value = dac_read();
00072     return (float)value * (1.0f / (float)0x3FF);
00073 }
00074 
00075 uint16_t analogout_read_u16(dac_t *obj) {
00076     uint32_t value = dac_read(); // 10-bit
00077     return (value << 6) | ((value >> 4) & 0x003F);
00078 }