Diff: SPI_flex.cpp

Revision:

0:9e3e70548ec3

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SPI_flex.cpp	Sat Mar 22 18:53:40 2014 +0000
@@ -0,0 +1,93 @@
+/* Class SPI_flex, Copyright 2014, David T. Mort (http://mbed.org/users/dtmort/)
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+#include "SPI_flex.h"
+#include "mbed.h"
+
+SPI_flex::SPI_flex(PinName mosi, PinName miso, PinName sclk, PinName cs):
+        _mosi(mosi), _miso(miso), _sclk(sclk), _cs(cs) {
+            _mosi=0;                            //initialize mosi pin
+            _sclk=0;                            //initialize serial clock pin
+            format();                           //initialize hardware length & mode
+            csactive();                        //initialize chip select setup active state
+            _cs=!__cs;                          //initialize chip select pin inactive
+}
+
+void SPI_flex::format(unsigned int bits, int mode){
+    BitString=bits;
+    if (mode<4){_mode=mode;}                     //test if 0-3
+    _cpol= _mode & 0x02;                         //extract clock polarity (idle state)
+    _cpha= _mode & 0x01;                         //extract clock phase (capture edge)
+}    
+
+
+void SPI_flex::csactive(bool cs){
+   __cs=cs;
+}
+
+void SPI_flex::frequency(int Hz){
+    Dcpwi= (400000-Hz)/14260;                   //set Delay clock pulse width inactive
+    Dcpwa= (400000-Hz)/14260;                   //set Delay clock pulse width active
+
+}
+
+void SPI_flex::select(void){
+    _deAssert=1;                                //initialze chip select bit counter
+    if (_cpol) _sclk=1; else _sclk=0;           //initialize sclk
+    _cs=__cs;                                   //assert chip select (SSEL)
+//    wait_us(1);                               //Tcss CS to SCLK Setup Time (+Dcpwi)  
+}    
+
+bool SPI_flex::writebit(bool bit){
+//        int id=500, ad=500;
+        int id=Dcpwi, ad=Dcpwa;                 //intialize frequency slowdown counters
+        if (_cs!=__cs)select();                 //assert cs auto-count sequence if not already engaged
+        if (_cpha) {_sclk =!_sclk;              //when 2nd clock edge capture (if CPHA=1)
+                    bit_read=_miso;}            //          read & store miso (if CPHA=1)
+        if (bit) _mosi=1; else _mosi=0;         //setup data on mosi
+        while(id){__nop(); id--;}               //Dcpwi Clock Pulse Width Inactive Delay (half period)
+        _sclk =!_sclk;                          //toggle sclk (capture edge)
+        while(ad){__nop(); ad--;}               //Dcpwa Clock Pulse Width Active Delay (half period)
+        _deAssert++;                            //advance chip select bit counter
+        if (_deAssert > BitString){deSelect();};//call function to latch data (while clock still active)
+        if (!_cpha) {_sclk =!_sclk;             //when 1st clock edge capture (if CPHA=0)
+                     bit_read=_miso;}           //          read & store miso (if CPHA=0)
+        return bit_read;
+}        
+
+uint8_t SPI_flex::writebyte(uint8_t byte){
+    int mask=0x80;                              //set MSB mask position
+    while (mask){                               //MSB -> LSB (7:0)
+        byte_read= mask &(writebit(byte & mask));  //write to mosi, read from miso
+        mask>>=1;}                              //move mask one position right
+    return byte_read;
+}
+
+uint16_t SPI_flex::writeword(uint16_t word){
+    int mask=0x8000;                            //set MSB mask position
+    while (mask){                               //MSB -> LSB (15:0)
+        word_read= mask &(writebit(word & mask));  //write to mosi, read from miso
+        mask>>=1;}                              //move mask one position right
+    return word_read;
+}
+
+ 
+
+
+void SPI_flex::deSelect(void){
+    _cs=!__cs;                                  //de-activate chip select while sclk is still active** on LSB
+    while(0){__nop();}                          //Tcspi Chip Select Pulse Inactive Time
+    _deAssert = 0;                              //reset chip select counter 
+    _mosi=0;                                    //reset mosi    
+}
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