SWSPI_HD.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_HD.h"
00025 
00026 SWSPI_HD::SWSPI_HD(PinName dio_pin, PinName sclk_pin, PinName cs_pin)
00027 {
00028     dio = new DigitalInOut(dio_pin);
00029     sclk = new DigitalOut(sclk_pin);
00030     cs = new DigitalOut(cs_pin,true);
00031     format(8);
00032     frequency();
00033 }
00034 
00035 SWSPI_HD::~SWSPI_HD()
00036 {
00037     delete dio;
00038     delete sclk;
00039     delete cs;
00040 }
00041 
00042 void SWSPI_HD::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_HD::frequency(int hz)
00052 {
00053     this->freq = hz;
00054 }
00055 
00056 int SWSPI_HD::write(int value)
00057 {
00058     int read = 0;
00059     //ensure clock is in right phase to start and disable slave device
00060     cs->write(true);
00061     sclk->write(!polarity);
00062     
00063     //Write Out
00064     dio->output();// set as an OUTPUT
00065     cs->write(false);//select slave device (active low)
00066     for (int bit = bits-1; bit >= 0; --bit)
00067     {
00068         dio->write(((value >> bit) & 0x01) != 0);
00069         wait(1.0/freq/2);
00070         sclk->write(!polarity);
00071         wait(1.0/freq/2);
00072         sclk->write(polarity);
00073     }
00074     
00075     //Read In
00076     dio->input();// set as an INPUT
00077     
00078     for (int bit = bits-1; bit >= 0; --bit)
00079     {
00080         if (phase == 0)
00081         {
00082             if (dio->read())   // was miso
00083                 read |= (1 << bit);
00084         }
00085         
00086         sclk->write(!polarity);
00087 
00088         wait(1.0/freq/2);
00089         
00090         if (phase == 1)
00091         {
00092             if (dio->read())   // was miso
00093                 read |= (1 << bit);
00094         }
00095 
00096         sclk->write(polarity);
00097 
00098         wait(1.0/freq/2);
00099     }
00100     cs->write(true);
00101     return read;
00102 }
00103