From b304adeecabaceda477ebf019b35437f46f5f78a Mon Sep 17 00:00:00 2001
From: iceman1001 <iceman@iuse.se>
Date: Sat, 22 Feb 2020 13:16:04 +0100
Subject: [PATCH] hitag, determine adc levels to get better demodulation

---
 armsrc/lfadc.c | 39 +++++++++++++++++++++++++++++----------
 armsrc/lfadc.h |  1 +
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/armsrc/lfadc.c b/armsrc/lfadc.c
index 04f293e1d..6b0eb930a 100644
--- a/armsrc/lfadc.c
+++ b/armsrc/lfadc.c
@@ -10,6 +10,7 @@
 #include "lfsampling.h"
 #include "fpgaloader.h"
 #include "ticks.h"
+#include "dbprint.h"
 
 // Sam7s has several timers, we will use the source TIMER_CLOCK1 (aka AT91C_TC_CLKS_TIMER_DIV1_CLOCK)
 // TIMER_CLOCK1 = MCK/2, MCK is running at 48 MHz, Timer is running at 48/2 = 24 MHz
@@ -46,13 +47,28 @@ bool lf_test_periods(size_t expected, size_t count) {
 // Low frequency (LF) adc passthrough functionality
 //////////////////////////////////////////////////////////////////////////////
 uint8_t previous_adc_val = 0;
+uint8_t adc_avg = 0;
+
+void lf_sample_mean(void) {
+    uint8_t periods = 0;
+    uint32_t adc_sum = 0;
+    while (periods < 32) {
+        if (AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
+            adc_sum += AT91C_BASE_SSC->SSC_RHR;
+            periods++;
+        }
+    }
+    // division by 32    
+    adc_avg = adc_sum >> 5;
+
+    if (DBGLEVEL >= DBG_EXTENDED)
+        Dbprintf("LF ADC average %u", adc_avg);
+}
 
 size_t lf_count_edge_periods_ex(size_t max, bool wait, bool detect_gap) {
     size_t periods = 0;
     volatile uint8_t adc_val;
-    //uint8_t avg_peak = 140, avg_through = 96;
-    // 140 - 127 - 114
-    uint8_t avg_peak = 140, avg_through = 106;
+    uint8_t avg_peak = adc_avg + 3, avg_through = adc_avg - 3;
     int16_t checked = 0;
 
     while (!BUTTON_PRESS()) {
@@ -98,8 +114,8 @@ size_t lf_count_edge_periods_ex(size_t max, bool wait, bool detect_gap) {
                     }
                 }
             }
-
             previous_adc_val = adc_val;
+
             if (periods >= max) return 0;
         }
     }
@@ -131,8 +147,9 @@ void lf_reset_counter() {
 bool lf_get_tag_modulation() {
     return (rising_edge == false);
 }
+
 bool lf_get_reader_modulation() {
-    return rising_edge;    
+    return rising_edge;
 }
 
 void lf_wait_periods(size_t periods) {
@@ -147,7 +164,7 @@ void lf_init(bool reader, bool simulate) {
 
     FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
 
-    FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
+    FpgaSendCommand(FPGA_CMD_SET_DIVISOR, LF_DIVISOR_134);
     if (reader) {
         FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC | FPGA_LF_ADC_READER_FIELD);
     } else {
@@ -168,8 +185,8 @@ void lf_init(bool reader, bool simulate) {
     // When in reader mode, give the field a bit of time to settle.
     // 313T0 = 313 * 8us = 2504us = 2.5ms  Hitag2 tags needs to be fully powered.
     if (reader) {
-        // 50 ms
-        SpinDelay(50);
+        // 10 ms
+        SpinDelay(10);
     }
 
     // Steal this pin from the SSP (SPI communication channel with fpga) and use it to control the modulation
@@ -195,7 +212,7 @@ void lf_init(bool reader, bool simulate) {
     AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
 
     // Prepare data trace
-    uint32_t bufsize = 20000;
+    uint32_t bufsize = 10000;
 
     // use malloc
     if (logging) initSampleBufferEx(&bufsize, true);
@@ -203,6 +220,8 @@ void lf_init(bool reader, bool simulate) {
     sample_config *sc = getSamplingConfig();
     sc->decimation = 1;
     sc->averaging = 0;
+    
+    lf_sample_mean();
 }
 
 void lf_finalize() {
@@ -275,7 +294,7 @@ static void lf_manchester_send_bit(uint8_t bit) {
     lf_modulation(bit != 0);
     lf_wait_periods(16);
     lf_modulation(bit == 0);
-    lf_wait_periods(16);
+    lf_wait_periods(32);
 }
 
 // simulation
diff --git a/armsrc/lfadc.h b/armsrc/lfadc.h
index 8c33aa778..09e5762c6 100644
--- a/armsrc/lfadc.h
+++ b/armsrc/lfadc.h
@@ -17,6 +17,7 @@
 
 extern bool logging;
 
+void lf_sample_mean(void);
 bool lf_test_periods(size_t expected, size_t count);
 size_t lf_count_edge_periods(size_t max);
 size_t lf_detect_gap(size_t max);