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 #if DEVICE_ANALOGOUT
00019 
00020 #include "cmsis.h"
00021 #include "pinmap.h"
00022 #include "error.h"
00023 
00024 static const PinMap PinMap_DAC[] = {
00025     {P0_26, DAC_0, 2},
00026     {NC   , NC   , 0}
00027 };
00028 
00029 void analogout_init(dac_t *obj, PinName pin) {
00030     obj->dac = (DACName)pinmap_peripheral(pin, PinMap_DAC);
00031     if (obj->dac == (uint32_t)NC) {
00032         error("DAC pin mapping failed");
00033     }
00034 
00035     // power is on by default, set DAC clk divider is /4
00036     LPC_SC->PCLKSEL0 &= ~(0x3 << 22);
00037 
00038     // map out (must be done before accessing registers)
00039     pinmap_pinout(pin, PinMap_DAC);
00040 
00041     analogout_write_u16(obj, 0);
00042 }
00043 
00044 void analogout_free(dac_t *obj) {}
00045 
00046 static inline void dac_write(int value) {
00047     value &= 0x3FF; // 10-bit
00048 
00049     // Set the DAC output
00050     LPC_DAC->DACR = (0 << 16)       // bias = 0
00051                   | (value << 6);
00052 }
00053 
00054 static inline int dac_read() {
00055     return (LPC_DAC->DACR >> 6) & 0x3FF;
00056 }
00057 
00058 void analogout_write(dac_t *obj, float value) {
00059     if (value < 0.0) {
00060         dac_write(0);
00061     } else if (value > 1.0) {
00062         dac_write(0x3FF);
00063     } else {
00064         dac_write(value * (float)0x3FF);
00065     }
00066 }
00067 
00068 void analogout_write_u16(dac_t *obj, uint16_t value) {
00069     dac_write(value >> 6); // 10-bit
00070 }
00071 
00072 float analogout_read(dac_t *obj) {
00073     uint32_t value = dac_read();
00074     return (float)value * (1.0f / (float)0x3FF);
00075 }
00076 
00077 uint16_t analogout_read_u16(dac_t *obj) {
00078     uint32_t value = dac_read(); // 10-bit
00079     return (value << 6) | ((value >> 4) & 0x003F);
00080 }
00081 
00082 #endif