FlapJackApps/libdc
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Teach the EON Steel about HDLC encoding of the command packets

Browse Source 
The BLE GATT transport ends up using HDLC for the stream encoding,
unlike the USB HID side.  The EON Steel BLE GATT protocol actually does
that for both the commands and for the replies, but this converts only
the command side, because that's the simpler one.

The reply side code will need to be re-architected a bit, because right
now it is very much oriented towards beign able to do everything one
single packet at a time (which is true for USB HID) rather than treating
the packets as a stream of data (as is necessary for the CRC32
verification and to handle the escaping of the 0x7e/0x7d bytes in the
stream).

So with this change, you can't actually do a download over BLE, but I
was able to verify that the first command transfers correctly, and the
EON Steel replies to it over Bluetooth LE GATT.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2017-06-22 21:44:28 -07:00
parent b7699b6985
commit c863db02f0
2 changed files with 61 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
examples/Makefile.am
View File

@ -1,5 +1,5 @@
AM_CPPFLAGS = -I$(top_builddir)/include -I$(top_srcdir)/include
LDADD = $(top_builddir)/src/libdivecomputer.la
LDADD = $(top_builddir)/src/libdivecomputer.la -lz
bin_PROGRAMS = \
dctool

61
src/suunto_eonsteel.c
View File

@ -22,6 +22,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <zlib.h> /* For crc32() */
#include "suunto_eonsteel.h"
#include "context-private.h"
@ -160,6 +161,42 @@ static int receive_packet(suunto_eonsteel_device_t *eon, unsigned char *buffer,
return len;
}
static int add_hdlc(unsigned char *dst, unsigned char val)
{
int chars = 1;
switch (val) {
case 0x7e: case 0x7d:
*dst++ = 0x7d;
val ^= 0x20;
chars++;
/* fallthrough */
default:
*dst = val;
}
return chars;
}
static int hdlc_reencode(unsigned char *dst, unsigned char *src, int len)
{
unsigned int crc = crc32(0, src, len);
int result = 0, i;
*dst++ = 0x7e; result++;
for (i = 0; i < len; i++) {
int chars = add_hdlc(dst, src[i]);
dst += chars;
result += chars;
}
for (i = 0; i < 4; i++) {
int chars = add_hdlc(dst, crc & 255);
dst += chars;
result += chars;
crc >>= 8;
}
*dst++ = 0x7e; result++;
return result;
}
static int send_cmd(suunto_eonsteel_device_t *eon,
unsigned short cmd,
unsigned int len,
@ -200,7 +237,29 @@ static int send_cmd(suunto_eonsteel_device_t *eon,
memcpy(buf+14, buffer, len);
}
rc = io->packet_write(io, buf, sizeof(buf), &transferred);
// BLE GATT protocol?
if (io->packet_size < 64) {
int hdlc_len;
unsigned char hdlc[2+2*(62+4)]; /* start/stop + escaping*(maxbuf+crc32) */
unsigned char *ptr;
hdlc_len = hdlc_reencode(hdlc, buf+2, buf[1]);
ptr = hdlc;
do {
int len = hdlc_len;
if (len > io->packet_size)
len = io->packet_size;
rc = io->packet_write(io, ptr, len, &transferred);
if (rc != DC_STATUS_SUCCESS)
break;
ptr += len;
hdlc_len -= len;
} while (hdlc_len);
} else {
rc = io->packet_write(io, buf, sizeof(buf), &transferred);
}
if (rc != DC_STATUS_SUCCESS) {
ERROR(eon->base.context, "write interrupt transfer failed");
return -1;