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GT-WT-02: exclude explicitly all zero sequence as false positive

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bugfix for computation of nibbles
code simplification
This commit is contained in:
Paul Ortyl
2015-08-20 22:05:26 +02:00
parent d9026ddecb
commit 5eb2deeef0
1 changed files with 24 additions and 19 deletions
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43
src/devices/gt_wt_02.c
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@@ -51,22 +51,24 @@ static int gt_wt_02_process_row(int row, const bitbuffer_t *bitbuffer)
const uint8_t *b = bitbuffer->bb[row];
const int length = bitbuffer->bits_per_row[row];
if ( 37 != length)
if ( 37 != length
|| !(b[0] || b[1] || b[2] || b[3] || b[4])) /* exclude all zeros */
return 0;
//fprintf(stderr, "GT-WT-02: %02x %02x %02x %02x %02x\n", b[0], b[1], b[2], b[3], b[4]);
fprintf(stderr, "GT-WT-02: %02x %02x %02x %02x %02x\n", b[0], b[1], b[2], b[3], b[4]);
// sum 8 nibbles (use 31 bits, the last one fill with 0 on 32nd bit)
const int sum_nimbbles = ((b[0] >> 4) & 0xF) + (b[0] & 0xF)
+ ((b[1] >> 4) & 0xF) + (b[1] & 0xF)
+ ((b[2] >> 4) & 0xF) + (b[2] & 0xF)
+ ((b[3] >> 4) & 0xF) + (b[3] & 0xe);
const int sum_nibbles =
(b[0] >> 4) + (b[0] & 0xF)
+ (b[1] >> 4) + (b[1] & 0xF)
+ (b[2] >> 4) + (b[2] & 0xF)
+ (b[3] >> 4) + (b[3] & 0xe);
// put last 6 bits into a number
const int checksum = ((b[3] & 1 )<<5) + (b[4]>>3);
// accept only correct checksums
if (sum_nimbbles != checksum)
// accept only correct checksums, (sum of nibbles modulo 64)
if ((sum_nibbles & 0x3F) != checksum)
return 0;
const int sensor_id = b[0]; /* 8 x A */
@@ -75,7 +77,7 @@ static int gt_wt_02_process_row(int row, const bitbuffer_t *bitbuffer)
const int channel = (b[1] >> 4 & 3); /* 2 x D */
const int negative_sign = (b[1] >> 3 & 1); /* 1 x E */
const int temp = (((b[1] & 15) << 8) | b[2]); /* E + 11 X G */
const int humidity = (b[3]>>1) & 0x7F;
const int humidity = (b[3]>>1);
float tempC = (negative_sign ? ( temp - (1<<12) ) : temp ) * 0.1F;
{
@@ -120,19 +122,22 @@ r_device gt_wt_02 = {
int main()
{
bitbuffer_t bb;
bb.num_rows = 3;
bb.num_rows = 1;
bb.bits_per_row[0] = 37;
bb.bits_per_row[1] = 37;
bb.bits_per_row[2] = 37;
const uint8_t b0[] = {0x34, 0x00, 0xed, 0x47, 0x60};
const uint8_t b1[] = {0x34, 0x8f, 0x87, 0x15, 0x90};
const uint8_t b2[] = {0x34, 0x00, 0xde, 0x77, 0x78};
const uint8_t b[4][5] =
{
{0x00, 0x00, 0x00, 0x00, 0x00}, // this one is excluded despite the correct checksum
{0x34, 0x00, 0xed, 0x47, 0x60},
{0x34, 0x8f, 0x87, 0x15, 0x90},
{0x34, 0x00, 0xde, 0x77, 0x78},
};
memcpy(bb.bb[0], b0, 5);
memcpy(bb.bb[1], b1, 5);
memcpy(bb.bb[2], b2, 5);
for(int i=0; i<4; i++)
{
memcpy(bb.bb[0], b[i], 5);
gt_wt_02_callback(&bb);
}
gt_wt_02_callback(&bb);
/*
* Result:
2015-08-16 19:08:16 GT-WT-02 Sensor 34: battery OK, channel 0, button 0, temperature 23.7 C / 74.7 F, humidity 35%