/* Copyright 2023 OneOfEleven * https://github.com/DualTachyon * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // code to 'try' and reduce the AM demodulator saturation problem // // that is until someone works out how to properly configure the BK chip ! #include #include "am_fix.h" #include "app/main.h" #include "board.h" #include "driver/bk4819.h" #include "external/printf/printf.h" #include "frequencies.h" #include "functions.h" #include "misc.h" #ifdef ENABLE_AM_FIX typedef struct { uint16_t reg_val; int8_t gain_dB; } __attribute__((packed)) t_gain_table; // REG_10 AGC gain table // // <15:10> ??? // // <9:8> = LNA Gain Short // 3 = 0dB < original value // 2 = -19dB // was -11 // 1 = -24dB // was -16 // 0 = -28dB // was -19 // // <7:5> = LNA Gain // 7 = 0dB // 6 = -2dB // 5 = -4dB < original value // 4 = -6dB // 3 = -9dB // 2 = -14dB // 1 = -19dB // 0 = -24dB // // <4:3> = MIXER Gain // 3 = 0dB < original value // 2 = -3dB // 1 = -6dB // 0 = -8dB // // <2:0> = PGA Gain // 7 = 0dB // 6 = -3dB < original value // 5 = -6dB // 4 = -9dB // 3 = -15dB // 2 = -21dB // 1 = -27dB // 0 = -33dB // 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 (but wrong) // static const int16_t lna_short_dB[] = { (-28), (-24), (-19), 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 hugely easier than writing code to do the same // static const t_gain_table gain_table[] = { {0x03BE, -7}, // 0 .. 3 5 3 6 .. 0dB -4dB 0dB -3dB .. -7dB original {0x0000,-93}, // 1 .. 0 0 0 0 .. -28dB -24dB -8dB -33dB .. -93dB {0x0008,-91}, // 2 .. 0 0 1 0 .. -28dB -24dB -6dB -33dB .. -91dB {0x0100,-89}, // 3 .. 1 0 0 0 .. -24dB -24dB -8dB -33dB .. -89dB {0x0020,-88}, // 4 .. 0 1 0 0 .. -28dB -19dB -8dB -33dB .. -88dB {0x0108,-87}, // 5 .. 1 0 1 0 .. -24dB -24dB -6dB -33dB .. -87dB {0x0028,-86}, // 6 .. 0 1 1 0 .. -28dB -19dB -6dB -33dB .. -86dB {0x0018,-85}, // 7 .. 0 0 3 0 .. -28dB -24dB 0dB -33dB .. -85dB {0x0200,-84}, // 8 .. 2 0 0 0 .. -19dB -24dB -8dB -33dB .. -84dB {0x0101,-83}, // 9 .. 1 0 0 1 .. -24dB -24dB -8dB -27dB .. -83dB {0x0208,-82}, // 10 .. 2 0 1 0 .. -19dB -24dB -6dB -33dB .. -82dB {0x0118,-81}, // 11 .. 1 0 3 0 .. -24dB -24dB 0dB -33dB .. -81dB {0x0038,-80}, // 12 .. 0 1 3 0 .. -28dB -19dB 0dB -33dB .. -80dB {0x0220,-79}, // 13 .. 2 1 0 0 .. -19dB -19dB -8dB -33dB .. -79dB {0x0201,-78}, // 14 .. 2 0 0 1 .. -19dB -24dB -8dB -27dB .. -78dB {0x0228,-77}, // 15 .. 2 1 1 0 .. -19dB -19dB -6dB -33dB .. -77dB {0x0218,-76}, // 16 .. 2 0 3 0 .. -19dB -24dB 0dB -33dB .. -76dB {0x0119,-75}, // 17 .. 1 0 3 1 .. -24dB -24dB 0dB -27dB .. -75dB {0x0240,-74}, // 18 .. 2 2 0 0 .. -19dB -14dB -8dB -33dB .. -74dB {0x0221,-73}, // 19 .. 2 1 0 1 .. -19dB -19dB -8dB -27dB .. -73dB {0x0248,-72}, // 20 .. 2 2 1 0 .. -19dB -14dB -6dB -33dB .. -72dB {0x0238,-71}, // 21 .. 2 1 3 0 .. -19dB -19dB 0dB -33dB .. -71dB {0x0219,-70}, // 22 .. 2 0 3 1 .. -19dB -24dB 0dB -27dB .. -70dB {0x0260,-69}, // 23 .. 2 3 0 0 .. -19dB -9dB -8dB -33dB .. -69dB {0x0241,-68}, // 24 .. 2 2 0 1 .. -19dB -14dB -8dB -27dB .. -68dB {0x0268,-67}, // 25 .. 2 3 1 0 .. -19dB -9dB -6dB -33dB .. -67dB {0x0280,-66}, // 26 .. 2 4 0 0 .. -19dB -6dB -8dB -33dB .. -66dB {0x0300,-65}, // 27 .. 3 0 0 0 .. 0dB -24dB -8dB -33dB .. -65dB {0x02A0,-64}, // 28 .. 2 5 0 0 .. -19dB -4dB -8dB -33dB .. -64dB {0x0308,-63}, // 29 .. 3 0 1 0 .. 0dB -24dB -6dB -33dB .. -63dB {0x02C0,-62}, // 30 .. 2 6 0 0 .. -19dB -2dB -8dB -33dB .. -62dB {0x0290,-61}, // 31 .. 2 4 2 0 .. -19dB -6dB -3dB -33dB .. -61dB {0x0320,-60}, // 32 .. 3 1 0 0 .. 0dB -19dB -8dB -33dB .. -60dB {0x0301,-59}, // 33 .. 3 0 0 1 .. 0dB -24dB -8dB -27dB .. -59dB {0x0328,-58}, // 34 .. 3 1 1 0 .. 0dB -19dB -6dB -33dB .. -58dB {0x0318,-57}, // 35 .. 3 0 3 0 .. 0dB -24dB 0dB -33dB .. -57dB {0x02C1,-56}, // 36 .. 2 6 0 1 .. -19dB -2dB -8dB -27dB .. -56dB {0x0340,-55}, // 37 .. 3 2 0 0 .. 0dB -14dB -8dB -33dB .. -55dB {0x0321,-54}, // 38 .. 3 1 0 1 .. 0dB -19dB -8dB -27dB .. -54dB {0x0348,-53}, // 39 .. 3 2 1 0 .. 0dB -14dB -6dB -33dB .. -53dB {0x0338,-52}, // 40 .. 3 1 3 0 .. 0dB -19dB 0dB -33dB .. -52dB {0x0319,-51}, // 41 .. 3 0 3 1 .. 0dB -24dB 0dB -27dB .. -51dB {0x0360,-50}, // 42 .. 3 3 0 0 .. 0dB -9dB -8dB -33dB .. -50dB {0x0341,-49}, // 43 .. 3 2 0 1 .. 0dB -14dB -8dB -27dB .. -49dB {0x0368,-48}, // 44 .. 3 3 1 0 .. 0dB -9dB -6dB -33dB .. -48dB {0x0380,-47}, // 45 .. 3 4 0 0 .. 0dB -6dB -8dB -33dB .. -47dB {0x0339,-46}, // 46 .. 3 1 3 1 .. 0dB -19dB 0dB -27dB .. -46dB {0x03A0,-45}, // 47 .. 3 5 0 0 .. 0dB -4dB -8dB -33dB .. -45dB {0x0361,-44}, // 48 .. 3 3 0 1 .. 0dB -9dB -8dB -27dB .. -44dB {0x03C0,-43}, // 49 .. 3 6 0 0 .. 0dB -2dB -8dB -33dB .. -43dB {0x0390,-42}, // 50 .. 3 4 2 0 .. 0dB -6dB -3dB -33dB .. -42dB {0x03E0,-41}, // 51 .. 3 7 0 0 .. 0dB 0dB -8dB -33dB .. -41dB {0x03B0,-40}, // 52 .. 3 5 2 0 .. 0dB -4dB -3dB -33dB .. -40dB {0x03E8,-39}, // 53 .. 3 7 1 0 .. 0dB 0dB -6dB -33dB .. -39dB {0x03D0,-38}, // 54 .. 3 6 2 0 .. 0dB -2dB -3dB -33dB .. -38dB {0x03C1,-37}, // 55 .. 3 6 0 1 .. 0dB -2dB -8dB -27dB .. -37dB {0x03F0,-36}, // 56 .. 3 7 2 0 .. 0dB 0dB -3dB -33dB .. -36dB {0x03E1,-35}, // 57 .. 3 7 0 1 .. 0dB 0dB -8dB -27dB .. -35dB {0x03B1,-34}, // 58 .. 3 5 2 1 .. 0dB -4dB -3dB -27dB .. -34dB {0x03F8,-33}, // 59 .. 3 7 3 0 .. 0dB 0dB 0dB -33dB .. -33dB {0x03D1,-32}, // 60 .. 3 6 2 1 .. 0dB -2dB -3dB -27dB .. -32dB {0x03C2,-31}, // 61 .. 3 6 0 2 .. 0dB -2dB -8dB -21dB .. -31dB {0x03F1,-30}, // 62 .. 3 7 2 1 .. 0dB 0dB -3dB -27dB .. -30dB {0x03E2,-29}, // 63 .. 3 7 0 2 .. 0dB 0dB -8dB -21dB .. -29dB {0x03B2,-28}, // 64 .. 3 5 2 2 .. 0dB -4dB -3dB -21dB .. -28dB {0x03F9,-27}, // 65 .. 3 7 3 1 .. 0dB 0dB 0dB -27dB .. -27dB {0x03D2,-26}, // 66 .. 3 6 2 2 .. 0dB -2dB -3dB -21dB .. -26dB {0x03C3,-25}, // 67 .. 3 6 0 3 .. 0dB -2dB -8dB -15dB .. -25dB {0x03F2,-24}, // 68 .. 3 7 2 2 .. 0dB 0dB -3dB -21dB .. -24dB {0x03E3,-23}, // 69 .. 3 7 0 3 .. 0dB 0dB -8dB -15dB .. -23dB {0x03B3,-22}, // 70 .. 3 5 2 3 .. 0dB -4dB -3dB -15dB .. -22dB {0x03FA,-21}, // 71 .. 3 7 3 2 .. 0dB 0dB 0dB -21dB .. -21dB {0x03D3,-20}, // 72 .. 3 6 2 3 .. 0dB -2dB -3dB -15dB .. -20dB {0x03C4,-19}, // 73 .. 3 6 0 4 .. 0dB -2dB -8dB -9dB .. -19dB {0x03F3,-18}, // 74 .. 3 7 2 3 .. 0dB 0dB -3dB -15dB .. -18dB {0x03E4,-17}, // 75 .. 3 7 0 4 .. 0dB 0dB -8dB -9dB .. -17dB {0x03C5,-16}, // 76 .. 3 6 0 5 .. 0dB -2dB -8dB -6dB .. -16dB {0x03FB,-15}, // 77 .. 3 7 3 3 .. 0dB 0dB 0dB -15dB .. -15dB {0x03E5,-14}, // 78 .. 3 7 0 5 .. 0dB 0dB -8dB -6dB .. -14dB {0x03C6,-13}, // 79 .. 3 6 0 6 .. 0dB -2dB -8dB -3dB .. -13dB {0x03F4,-12}, // 80 .. 3 7 2 4 .. 0dB 0dB -3dB -9dB .. -12dB {0x03E6,-11}, // 81 .. 3 7 0 6 .. 0dB 0dB -8dB -3dB .. -11dB {0x03C7,-10}, // 82 .. 3 6 0 7 .. 0dB -2dB -8dB 0dB .. -10dB {0x03FC, -9}, // 83 .. 3 7 3 4 .. 0dB 0dB 0dB -9dB .. -9dB {0x03E7, -8}, // 84 .. 3 7 0 7 .. 0dB 0dB -8dB 0dB .. -8dB {0x03BE, -7}, // 85 .. 3 5 3 6 .. 0dB -4dB 0dB -3dB .. -7dB original {0x03FD, -6}, // 86 .. 3 7 3 5 .. 0dB 0dB 0dB -6dB .. -6dB {0x03DE, -5}, // 87 .. 3 6 3 6 .. 0dB -2dB 0dB -3dB .. -5dB {0x03BF, -4}, // 88 .. 3 5 3 7 .. 0dB -4dB 0dB 0dB .. -4dB {0x03FE, -3}, // 89 .. 3 7 3 6 .. 0dB 0dB 0dB -3dB .. -3dB {0x03DF, -2}, // 90 .. 3 6 3 7 .. 0dB -2dB 0dB 0dB .. -2dB {0x03FF, 0}, // 91 .. 3 7 3 7 .. 0dB 0dB 0dB 0dB .. 0dB }; static const unsigned int original_index = 90; #ifdef ENABLE_AM_FIX_SHOW_DATA // display update rate static const unsigned int display_update_rate = 250 / 10; // max 250ms display update rate unsigned int counter = 0; #endif unsigned int gain_table_index[2] = {original_index, original_index}; // used simply to detect a changed gain setting unsigned int gain_table_index_prev[2] = {0, 0}; // holds the previous RSSI level .. we do an average of old + new RSSI reading int16_t prev_rssi[2] = {0, 0}; // to help reduce gain hunting, peak hold count down tick unsigned int hold_counter[2] = {0, 0}; // used to correct the RSSI readings after our RF gain adjustments int16_t rssi_gain_diff[2] = {0, 0}; // used to limit the max RF gain const unsigned max_index = ARRAY_SIZE(gain_table) - 1; // -89dBm, any higher and the AM demodulator starts to saturate/clip/distort const int16_t desired_rssi = (-89 + 160) * 2; void AM_fix_init(void) { // called at boot-up for (int i = 0; i < 2; i++) { gain_table_index[i] = original_index; // re-start with original QS setting } } void AM_fix_reset(const unsigned vfo) { // reset the AM fixer upper if (vfo > 1) return; #ifdef ENABLE_AM_FIX_SHOW_DATA counter = 0; #endif prev_rssi[vfo] = 0; hold_counter[vfo] = 0; rssi_gain_diff[vfo] = 0; gain_table_index_prev[vfo] = 0; } // adjust the RX 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 setting // void AM_fix_10ms(const unsigned vfo, bool force) { if(vfo > 1) return; if(!force) switch (gCurrentFunction) { case FUNCTION_TRANSMIT: case FUNCTION_BAND_SCOPE: case FUNCTION_POWER_SAVE: case FUNCTION_FOREGROUND: #ifdef ENABLE_AM_FIX_SHOW_DATA counter = display_update_rate; // queue up a display update as soon as we switch to RX mode #endif AM_fix_reset(vfo); return; // only adjust stuff if we're in one of these modes case FUNCTION_RECEIVE: case FUNCTION_MONITOR: case FUNCTION_INCOMING: break; } #ifdef ENABLE_AM_FIX_SHOW_DATA if (counter > 0) { if (++counter >= display_update_rate) { // trigger a display update counter = 0; gUpdateDisplay = true; } } #endif int16_t rssi; { // sample the current RSSI level // average it with the previous rssi (a bit of noise/spike immunity) const int16_t new_rssi = BK4819_GetRSSI(); rssi = (prev_rssi[vfo] > 0) ? (prev_rssi[vfo] + new_rssi) / 2 : new_rssi; prev_rssi[vfo] = new_rssi; } #ifdef ENABLE_AM_FIX_SHOW_DATA { int16_t new_rssi = rssi - rssi_gain_diff[vfo]; if (gCurrentRSSI[vfo] != new_rssi) { // rssi changed gCurrentRSSI[vfo] = new_rssi; if (counter == 0) { counter = 1; gUpdateDisplay = true; // trigger a display update } } } #endif // automatically adjust the RF RX gain // update the gain hold counter if (hold_counter[vfo] > 0) hold_counter[vfo]--; // dB difference between actual and desired RSSI level int16_t diff_dB = (rssi - desired_rssi) / 2; if (diff_dB > 0) { // decrease gain unsigned int index = gain_table_index[vfo]; // current position we're at if (diff_dB >= 10) { // jump immediately to a new gain setting // this greatly speeds up initial gain reduction (but reduces noise/spike immunity) const int16_t desired_gain_dB = (int16_t)gain_table[index].gain_dB - diff_dB + 8; // get no closer than 8dB (bit of noise/spike immunity) // scan the table to see what index to jump straight too while (index > 1) if (gain_table[--index].gain_dB <= desired_gain_dB) break; } else { // incrementally reduce the gain .. taking it slow improves noise/spike immunity if (index > 1) index--; // slow step-by-step gain reduction } index = (index < 1) ? 1 : (index > max_index) ? max_index : index; if (gain_table_index[vfo] != index) { gain_table_index[vfo] = index; hold_counter[vfo] = 30; // 300ms hold } } if (diff_dB >= -6) // 6dB hysterisis (help reduce gain hunting) hold_counter[vfo] = 30; // 300ms hold if (hold_counter[vfo] == 0) { // hold has been released, we're free to increase gain const unsigned int index = gain_table_index[vfo] + 1; // move up to next gain index gain_table_index[vfo] = (index <= max_index) ? index : max_index; // limit the gain index } { // apply the new settings to the front end registers const unsigned int index = gain_table_index[vfo]; // remember the new table index gain_table_index_prev[vfo] = index; BK4819_WriteRegister(BK4819_REG_13, gain_table[index].reg_val); // offset the RSSI reading to the rest of the firmware to cancel out the gain adjustments we make // RF gain difference from original QS setting rssi_gain_diff[vfo] = ((int16_t)gain_table[index].gain_dB - gain_table[original_index].gain_dB) * 2; } // save the corrected RSSI level gCurrentRSSI[vfo] = rssi - rssi_gain_diff[vfo]; #ifdef ENABLE_AM_FIX_SHOW_DATA if (counter == 0) { counter = 1; gUpdateDisplay = true; } #endif } #ifdef ENABLE_AM_FIX_SHOW_DATA void AM_fix_print_data(const unsigned vfo, char *s) { if (s != NULL && vfo < ARRAY_SIZE(gain_table_index)) { const unsigned int index = gain_table_index[vfo]; sprintf(s, "%2u %4ddB %3u", index, gain_table[index].gain_dB, prev_rssi[vfo]); counter = 0; } } #endif int16_t AM_fix_get_rssi_gain_diff(const unsigned vfo) { if(vfo > 1) return 0; return rssi_gain_diff[vfo]; } #endif