Reformat; add better algorithm to find bits.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@3007 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/net/afsk.c b/bertos/net/afsk.c
index 2472861cebba58247ccd6a822659d0cfa52979f4..331784549517a6bc8eac9273f8c0dfccd5ac3e26 100644 (file)
--- a/bertos/net/afsk.c
+++ b/bertos/net/afsk.c
@@ -151,6 +151,7 @@ static uint8_t tx_buf[CONFIG_AFSK_TX_BUFLEN];
 
 static int16_t iir_x[2];
 static int16_t iir_y[2];
+
 static uint8_t sampled_bits;
 static uint8_t found_bits;
 static uint8_t demod_bits;
@@ -249,8 +250,12 @@ DEFINE_AFSK_ADC_ISR()
 
        iir_x[0] = iir_x[1];
 
-       #if (CONFIG_AFSK_FILTER == AFSK_BUTTERWORTH) || (CONFIG_AFSK_FILTER == AFSK_CHEBYSHEV)
+       #if (CONFIG_AFSK_FILTER == AFSK_BUTTERWORTH)
+               iir_x[1] = ((int8_t)fifo_pop(&delay_fifo) * curr_sample) >> 2;
+               //iir_x[1] = ((int8_t)fifo_pop(&delay_fifo) * curr_sample) / 6.027339492;
+       #elif (CONFIG_AFSK_FILTER == AFSK_CHEBYSHEV)
                iir_x[1] = ((int8_t)fifo_pop(&delay_fifo) * curr_sample) >> 2;
+               //iir_x[1] = ((int8_t)fifo_pop(&delay_fifo) * curr_sample) / 3.558147322;
        #else
                #error Filter type not found!
        #endif
@@ -266,12 +271,14 @@ DEFINE_AFSK_ADC_ISR()
                 * = iir >> 1 + iir >> 3 + iir >> 5
                 */
                iir_y[1] = iir_x[0] + iir_x[1] + (iir_y[0] >> 1) + (iir_y[0] >> 3) + (iir_y[0] >> 5);
+               //iir_y[1] = iir_x[0] + iir_x[1] + iir_y[0] * 0.6681786379;
        #elif CONFIG_AFSK_FILTER == AFSK_CHEBYSHEV
                /*
                 * This should be (iir_y[0] * 0.438) but
                 * (iir_y[0] >> 1) is a faster approximation :-)
                 */
                iir_y[1] = iir_x[0] + iir_x[1] + (iir_y[0] >> 1);
+               //iir_y[1] = iir_x[0] + iir_x[1] + iir_y[0] * 0.4379097269;
        #endif
 
        /* Save this sampled bit in a delay line */
@@ -300,10 +307,17 @@ DEFINE_AFSK_ADC_ISR()
                found_bits <<= 1;
 
                /*
-                * TODO: maybe a better algorithm to find the sample bit
-                * other than reading the last one.
+                * Determine bit value by reading the last 3 sampled bits.
+                * If the number of ones is two or greater, the bit value it's a 1,
+                * otherwise it's a 0.
                 */
-               found_bits |= sampled_bits & 1;
+               uint8_t bits = sampled_bits & 0x07;
+               if (bits == 0x07 // 111, 3 bits set to 1
+                || bits == 0x06 // 110, 2 bits
+                || bits == 0x05 // 101, 2 bits
+                || bits == 0x03 // 011, 2 bits
+               )
+                       found_bits |= 1;
 
                /*
                 * NRZI coding: if 2 consecutive bits have the same value