SWSPI.cpp

00001 /* SWSPI, Software SPI library
00002  * Copyright (c) 2012-2014, David R. Van Wagner, http://techwithdave.blogspot.com
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
00020  * THE SOFTWARE.
00021  */
00022 
00023 #include <mbed.h>
00024 #include "SWSPI.h"
00025 
00026 SWSPI::SWSPI(PinName mosi_pin, PinName miso_pin, PinName sclk_pin):_fast(false)
00027 {
00028     mosi = new DigitalOut(mosi_pin);
00029     miso = new DigitalIn(miso_pin);
00030     sclk = new DigitalOut(sclk_pin);
00031     format(8);
00032     frequency();
00033 }
00034 
00035 SWSPI::~SWSPI()
00036 {
00037     delete mosi;
00038     delete miso;
00039     delete sclk;
00040 }
00041 
00042 void SWSPI::format(int bits, int mode)
00043 {
00044     this->bits = bits;
00045     this->mode = mode;
00046     polarity = (mode >> 1) & 1;
00047     phase = mode & 1;
00048     sclk->write(polarity);
00049 }
00050 
00051 void SWSPI::frequency(int hz)
00052 {
00053     this->freq = hz;
00054     _fast = (hz >= 1000000) ? true : false;
00055 }
00056 
00057 #pragma Otime
00058 
00059 int SWSPI::write(int value)
00060 {
00061     if (_fast) {
00062         return fast_write(value);
00063     }
00064     int read = 0;
00065     for (int bit = bits-1; bit >= 0; --bit)
00066     {
00067         mosi->write(((value >> bit) & 0x01) != 0);
00068 
00069         if (phase == 0)
00070         {
00071             if (miso->read())
00072                 read |= (1 << bit);
00073         }
00074 
00075         sclk->write(!polarity);
00076 
00077         wait_us(1000000/freq/2);
00078 
00079         if (phase == 1)
00080         {
00081             if (miso->read())
00082                 read |= (1 << bit);
00083         }
00084 
00085         sclk->write(polarity);
00086 
00087         wait_us(1000000/freq/2);
00088     }
00089     
00090     return read;
00091 }
00092 
00093 uint8_t SWSPI::fast_write(uint8_t value)
00094 {
00095     uint8_t data = 0;
00096     for(uint8_t mask = 0x80; mask; mask >>= 1) {
00097         mosi->write((value & mask) ? 1 : 0);
00098         if (miso->read()) {
00099             data |= mask;
00100         }
00101         sclk->write(1);
00102         sclk->write(0);
00103     }
00104     return data;
00105 }
00106