main.cpp

00001 #include "mbed.h"
00002 
00003 //#include <stdarg.h>
00004 #include <stdio.h>
00005 #include <stdlib.h>
00006 #include <string.h>
00007 
00008 /*
00009 Instructions for use: connect the mbed to a parallel port using these connexions.
00010 use a terminal program to connect via USB to the mbed side. */
00011 
00012 /* This is for testing since it uses the serial port at 9600 bauds to connect to a PC */
00013 
00014 #define PAR_INVERT_OBF_SIGNAL
00015 
00016 #define PAR_8255_SEND_MASK      0x80
00017 #define PAR_8255_RECV_MASK      0x40
00018 
00019 /*
00020   8255          Parallel    Pin     Bit
00021   PC7   /OBF    ->  /ACK        10      6
00022   PC6   /ACK    <-  /SLCTIN     17      3
00023   PC5   IBF     ->  BUSY        11      7
00024   PC4   /STB    <-  /STB        1       0
00025 
00026 15 nError       -> p9       not used
00027 13 Select       -> p10      not used
00028 12 PE           -> p11      not used
00029 11 Busy         -> p12      IBF
00030 10 nAck         -> p13      /OBF
00031 
00032  1 nStrobe      -> p14      /STB
00033 14 nAutoFeed    -> p15      not used
00034 16 nInit        -> p16      not used
00035 17 nSelectIn    -> p17      /ACK
00036 */
00037 
00038 DigitalOut IBF(p12); // IBF
00039 DigitalOut nOBF(p13); // /OBF
00040 
00041 InterruptIn nSTB(p14);
00042 InterruptIn nACK(p17);
00043 
00044 /*
00045 D0 p30  p0.4
00046 D1 p29  p0.5
00047 D2 p8   p0.6
00048 D3 p7   p0.7
00049 D4 p6   p0.8
00050 D5 p5   p0.9
00051 D6 p28  p0.10
00052 D7 p27  p0.11
00053 */
00054 BusInOut PtrData(p30,p29,p8,p7,p6,p5,p28,p27);
00055 
00056 #define __DOUTBUFSIZE 256
00057 #define __DINBUFSIZE 256
00058 char __outstr[__DOUTBUFSIZE];
00059 char __instr[__DINBUFSIZE];
00060 
00061 Serial pc(USBTX, USBRX); // tx, rx
00062 
00063 unsigned char rx_data;
00064 
00065 // Peripheral should check that there is no output pending from the 8255 to the peripheral before writing to the 8255
00066 
00067 // When /STB is falling
00068 void perif2mbed(void)
00069 {
00070     // read byte from peripheral
00071     rx_data = PtrData;
00072     IBF = 1;
00073 }
00074 
00075 // When /ACK is rising
00076 void mbed2perif(void)
00077 {
00078     nOBF = 1;
00079     PtrData.input();
00080 }
00081 
00082 void write_byte(unsigned char out)
00083 {
00084     // wait for /OBF = 1 and no read cycle in progress for politeness
00085     while ((nOBF == 0) || (IBF == 1));
00086 
00087     PtrData = out;
00088     PtrData.output();
00089     nOBF = 0;
00090 }
00091 
00092 unsigned char read_byte(void)
00093 {
00094     while (IBF == 0);
00095     IBF = 0;
00096     return rx_data;
00097 }
00098 
00099 int main()
00100 {
00101     PtrData.input();
00102 
00103     /* 9600 baud serial port */
00104     pc.printf("8255 emulator on mbed\r\n\n");
00105     
00106     IBF = 0;
00107     nOBF = 1;
00108     nSTB.fall(&perif2mbed);
00109     nACK.rise(&mbed2perif);
00110 
00111     PtrData.input();
00112 
00113     while(1)
00114     {
00115         // bytes from peripherals to 8255
00116         if (IBF == 1)
00117         {
00118             IBF = 0;
00119             pc.putc(rx_data);
00120         }
00121         else
00122         {
00123             if (pc.readable())
00124             {
00125                 write_byte(pc.getc());
00126             }
00127         }  
00128     }
00129 }