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Code Issues Releases Activity

Re-enabled weak signal bandwidth reduction

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OneOfEleven
2023-09-24 13:00:02 +01:00
parent 4ea37929f7
commit 2486501332
13 changed files with 906 additions and 23 deletions
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63
am_fix.c
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@ -92,14 +92,20 @@ const uint8_t orig_pga = 6; // -3dB
// 1 = -27dB
// 0 = -33dB
// front end register dB values - needs a measuring/calibration update really
// front end register dB values
//
// these values need to be accurate for the code to properly/reliably switch
// between table entries when adjusting the front end registers.
//
// these 4 tables need a measuring/calibration update
//
// static const int16_t lna_short_dB[] = {-19, -16, -11, 0}; // was
static const int16_t lna_short_dB[] = {-33, -30 -24, 0}; // corrected'ish
static const int16_t lna_dB[] = {-24, -19, -14, -9, -6, -4, -2, 0};
static const int16_t mixer_dB[] = { -8, -6, -3, 0};
static const int16_t pga_dB[] = {-33, -27, -21, -15, -9, -6, -3, 0};
// lookup table is by far easier than writing code to do the same
// lookup table is hugely easier than writing code to do the same
//
static const t_am_fix_gain_table am_fix_gain_table[] =
{
@ -115,7 +121,7 @@ const uint8_t orig_pga = 6; // -3dB
{2, 2, 3, 6}, // 3 .. -24dB -14dB 0dB -3dB .. -41dB
{3, 2, 3, 6} // 4 .. 0dB -14dB 0dB -3dB .. -17dB
};
const unsigned int original_index = 1;
#elif 0
@ -288,6 +294,8 @@ const uint8_t orig_pga = 6; // -3dB
#else
unsigned int am_fix_gain_table_index = original_index; // start with original QS setting
#endif
// used to simply detect we've changed our table index/register settings
unsigned int am_fix_gain_table_index_prev = 0;
// moving average RSSI buffer
@ -299,14 +307,15 @@ const uint8_t orig_pga = 6; // -3dB
uint16_t sum; // sum of all samples in the buffer
} moving_avg_rssi = {0};
// used to prevent gain hunting, provides a peak hold time delay
// to help reduce gain hunting, provides a peak hold time delay
unsigned int am_gain_hold_counter = 0;
// used to correct the RSSI readings after our front end gain adjustments
int16_t rssi_db_gain_diff = 0;
void AM_fix_reset(void)
{
{ // reset the AM fixer
// reset the moving average filter
memset(&moving_avg_rssi, 0, sizeof(moving_avg_rssi));
@ -319,9 +328,17 @@ const uint8_t orig_pga = 6; // -3dB
#else
am_fix_gain_table_index = original_index; // re-start with original QS setting
#endif
am_fix_gain_table_index_prev = 0;
}
// adjust the RX RF gain to try and prevent the AM demodulator from
// saturating/overloading/clipping (distorted AM audio)
//
// we're actually doing the BK4819's job for it here, but as the chip
// won't/don't do it for itself, we're left to bodging it ourself by
// playing with the RF front end gain settings
//
void AM_fix_adjust_frontEnd_10ms(void)
{
#ifndef ENABLE_AM_FIX_TEST1
@ -329,12 +346,13 @@ const uint8_t orig_pga = 6; // -3dB
const uint16_t desired_rssi = (-89 + 160) * 2; // dBm to ADC sample
#endif
// we don't play with the front end gains if in FM mode
// they remain as per QS original
// we don't need to play with the front end gains if we're in FM mode, they
// remain as per QS original
//
if (!gRxVfo->IsAM)
return;
// we're in AM mode
// but we're not in FM mode, we're in AM mode
switch (gCurrentFunction)
{
@ -344,7 +362,7 @@ const uint8_t orig_pga = 6; // -3dB
case FUNCTION_FOREGROUND:
return;
// only adjust the front end if in one of these modes
// only adjust stuff if we're in one of these modes
case FUNCTION_RECEIVE:
case FUNCTION_MONITOR:
case FUNCTION_INCOMING:
@ -352,10 +370,11 @@ const uint8_t orig_pga = 6; // -3dB
}
// sample the current RSSI level
uint16_t rssi = BK4819_GetRSSI(); // supposed 9-bit value (0 .. 511) - never seen that though
uint16_t rssi = BK4819_GetRSSI(); // supposed 9-bit value (0 .. 511) - never seen that though
#if 1
// compute a moving average RSSI - just smooths any sharp spikes
// compute moving average RSSI - helps smooth any sharp spikes/troughs
// but can cause gain hunting/oscillation if too long a buffer (.samples)
if (moving_avg_rssi.count < ARRAY_SIZE(moving_avg_rssi.samples))
moving_avg_rssi.count++;
moving_avg_rssi.sum -= moving_avg_rssi.samples[moving_avg_rssi.index]; // subtract the oldest sample
@ -370,42 +389,42 @@ const uint8_t orig_pga = 6; // -3dB
#ifdef ENABLE_AM_FIX_TEST1
// user is manually adjusting a gain register - don't do anything automatically
am_fix_gain_table_index = 1 + gSetting_AM_fix_test1;
if (am_gain_hold_counter > 0)
if (--am_gain_hold_counter > 0)
return;
am_gain_hold_counter = 250; // 250ms
am_gain_hold_counter = 250; // 250ms hold
#else
// automatically choose a front end gain setting by monitoring the RSSI
if (rssi > desired_rssi)
{ // decrease gain
if (am_fix_gain_table_index > 1)
am_fix_gain_table_index--;
am_gain_hold_counter = 50; // 500ms
am_gain_hold_counter = 50; // 500ms hold
}
if (am_gain_hold_counter > 0)
am_gain_hold_counter--;
if (am_gain_hold_counter == 0)
{ // hold has been released, we're now free to increase gain
// hold has been released, we're free to increase gain
if (rssi < (desired_rssi - 10)) // 5dB hysterisis (helps reduce gain hunting)
{ // increase gain
// increase gain
if (am_fix_gain_table_index < (ARRAY_SIZE(am_fix_gain_table) - 1))
am_fix_gain_table_index++;
}
}
if (am_fix_gain_table_index == am_fix_gain_table_index_prev)
return; // no gain changes have been made
#endif
// apply the new settings to the front end registers
@ -423,6 +442,7 @@ const uint8_t orig_pga = 6; // -3dB
// gain difference from original QS setting
rssi_db_gain_diff = am_dB_gain - orig_dB_gain;
// shall we or sharn't we ?
//gCurrentRSSI[gEeprom.RX_CHANNEL] = rssi - (rssi_db_gain_diff * 2);
}
@ -430,6 +450,7 @@ const uint8_t orig_pga = 6; // -3dB
am_fix_gain_table_index_prev = am_fix_gain_table_index;
#ifdef ENABLE_AM_FIX_SHOW_DATA
// trigger display update so the user can see the data as it changes
gUpdateDisplay = true;
#endif
}