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Implemented checksumming

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This commit is contained in:
Mark Qvist 2014-04-04 17:05:53 +02:00
parent b350d3cd8c
commit 0c4bc75be9
6 changed files with 67 additions and 16 deletions
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33
Modem/protocol/mp1.c
View file

@ -1,12 +1,13 @@
#include "mp1.h"
#include <string.h>
#include <drv/ser.h>
//#include <ctype.h>
static void mp1Decode(MP1 *mp1) {
MP1Packet packet; // A decoded packet struct
uint8_t *buffer = mp1->buffer; // Get the buffer from the protocol context
packet.dataLength = mp1->packetLength;
packet.dataLength = mp1->packetLength - 1;
packet.data = buffer;
if (mp1->callback) mp1->callback(&packet);
@ -25,12 +26,24 @@ void mp1Poll(MP1 *mp1) {
// frame length, which means the flag signifies
// the end of the packet. Pass control to the
// decoder.
mp1Decode(mp1);
kprintf("Got checksum: %d.\n", mp1->buffer[mp1->packetLength-1]);
if ((mp1->checksum_in & 0xff) == 0x00) {
//kprintf("Correct checksum. Found %d.\n", mp1->buffer[mp1->packetLength-1]);
mp1Decode(mp1);
} else {
// Checksum was incorrect
mp1Decode(mp1);
//kprintf("Incorrect checksum. Found %d.\n", mp1->buffer[mp1->packetLength]);
//kprintf("should be %d", mp1->checksum_in);
}
}
// If the above is not the case, this must be the
// beginning of a frame
mp1->reading = true;
mp1->packetLength = 0;
mp1->checksum_in = MP1_CHECKSUM_INIT;
//kprintf("Checksum init with %d\n", mp1->checksum_in);
// We have indicated that we are reading,
// and reset the length counter. Now we'll
// continue to the next byte.
@ -59,6 +72,8 @@ void mp1Poll(MP1 *mp1) {
// If the length of the current incoming frame is
// still less than our max length, put the incoming
// byte in the buffer.
if (!mp1->escape) mp1->checksum_in = mp1->checksum_in ^ byte;
//kprintf("Checksum is now %d\n", mp1->checksum_in);
mp1->buffer[mp1->packetLength++] = byte;
} else {
// If not, we have a problem: The buffer has overrun
@ -95,13 +110,25 @@ void mp1Send(MP1 *mp1, const void *_buffer, size_t length) {
// Get the transmit data buffer
const uint8_t *buffer = (const uint8_t *)_buffer;
// Initialize checksum
mp1->checksum_out = MP1_CHECKSUM_INIT;
//kprintf("Checksum init with %d\n", mp1->checksum_out);
// Transmit the HDLC_FLAG to signify start of TX
kfile_putc(HDLC_FLAG, mp1->modem);
// Continously increment the pointer address
// of the buffer while passing it to the byte
// output function
while (length--) mp1Putbyte(mp1, *buffer++);
while (length--) {
mp1->checksum_out = mp1->checksum_out ^ *buffer;
//kprintf("Checksum is now %d\n", mp1->checksum_out);
mp1Putbyte(mp1, *buffer++);
}
// Write checksum to end of packet
kprintf("Checksum of this packet is %d\n", mp1->checksum_out);
mp1Putbyte(mp1, mp1->checksum_out);
// Transmit a HDLC_FLAG to signify end of TX
kfile_putc(HDLC_FLAG, mp1->modem);

7
Modem/protocol/mp1.h
View file

@ -4,9 +4,10 @@
#include <cfg/compiler.h>
#include <io/kfile.h>
// Frame sizing
#define MP1_MIN_FRAME_LENGTH 1
// Frame sizing & checksum
#define MP1_MIN_FRAME_LENGTH 3
#define MP1_MAX_FRAME_LENGTH 300
#define MP1_CHECKSUM_INIT 0xAA
// We need to know some basic HDLC flag bytes
#define HDLC_FLAG 0x7E
@ -26,6 +27,8 @@ typedef struct MP1 {
KFile *modem; // KFile access to the modem
size_t packetLength; // Counter for received packet length
mp1_callback_t callback; // The function to call when a packet has been received
uint8_t checksum_in; // Rolling checksum for incoming packets
uint8_t checksum_out; // Rolling checksum for outgoing packets
bool reading; // True when we have seen a HDLC flag
bool escape; // We need to know if we are in an escape sequence
} MP1;