From 8584158b58eaf0466562aa7540bb5e86875dede8 Mon Sep 17 00:00:00 2001
From: erikkaashoek <erik@kaashoek.com>
Date: Sun, 14 Jun 2020 13:14:11 +0200
Subject: [PATCH] Fast sweep added

---
 nanovna.h | 10 ++++++++++
 sa_core.c |  5 +++++
 si4432.c  | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/nanovna.h b/nanovna.h
index d0bbed3..813e4e4 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -29,6 +29,8 @@
 #define __MEASURE__
 #define __SELFTEST__
 #define __CALIBRATE__
+#define __FAST_SWEEP__          // Pre-fill SI4432 RSSI buffer  to get fastest sweep in zero span mode
+
 //#define __ULTRA__             // Add harmonics mode on low input.
 //#define __ULTRA_SA__            // Adds ADF4351 control for extra high 1st IF stage
 #define __SPUR__                // Does spur reduction by shifting IF
@@ -602,7 +604,12 @@ void reset_settings(int m);
 #define S_IS_AUTO(x) ((x)&2)
 #define S_STATE(X) ((X)&1)
 enum { S_OFF=0, S_ON=1, S_AUTO_OFF=2, S_AUTO_ON=3 };
+
+#ifdef __FAST_SWEEP__
+#define MINIMUM_SWEEP_TIME  3     // Minimum sweep time on zero span in miliseconds
+#else
 #define MINIMUM_SWEEP_TIME  15     // Minimum sweep time on zero span in miliseconds
+#endif
 #define REPEAT_TIME        134.0         // Time per extra repeat in uS
 #define MEASURE_TIME       175.0        // Time per vbwstep without stepdelay in uS
 
@@ -807,6 +814,9 @@ byte SI4432_Read_Byte( byte ADR );
 void SI4432_Init(void);
 void SI4432_Drive(int);
 float SI4432_RSSI(uint32_t i, int s);
+#ifdef __FAST_SWEEP__
+void SI4432_Fill(int s);
+#endif
 void SI4432_Set_Frequency ( long Freq );
 float SI4432_SET_RBW(float WISH);
 void SI4432_SetReference(int freq);
diff --git a/sa_core.c b/sa_core.c
index f58652c..20f0342 100644
--- a/sa_core.c
+++ b/sa_core.c
@@ -1291,6 +1291,11 @@ float perform(bool break_on_operation, int i, uint32_t f, int tracking)
     float signal_path_loss;
 
  skip_LO_setting:
+#ifdef __FAST_SWEEP__
+    if (i == 0 && setting.frequency_step == 0 && setting.trigger == T_AUTO && actualStepDelay == 0 && setting.repeat == 1 && actualStepDelay < 1000) {
+      SI4432_Fill(MODE_SELECT(setting.mode));
+    }
+#endif
 
 #ifdef __ULTRA__
     if (setting.mode == M_ULTRA)
diff --git a/si4432.c b/si4432.c
index ad97347..18a0e14 100644
--- a/si4432.c
+++ b/si4432.c
@@ -315,6 +315,33 @@ void SI4432_Set_Frequency ( long Freq ) {
 int actualStepDelay = 1500;
 //extern int setting.repeat;
 
+#ifdef __FAST_SWEEP__
+extern char age[POINTS_COUNT];
+static int buf_index = 0;
+static bool  buf_read = false;
+
+void SI4432_Fill(int s)
+{
+  SI4432_Sel = s;
+  int sel = SI_nSEL[SI4432_Sel];
+  float t = setting.sweep_time - calc_min_sweep_time(); // Time to delay in mS
+  if (t < 0)
+    t = 0;
+  int ti = t * 1000 / 290.0;                         // Now in uS per point      if (t < 30000)
+  for (int i=0; i<POINTS_COUNT; ) {
+    SPI2_CLK_LOW;
+    palClearPad(GPIOC, sel);
+    shiftOut( 0x26 );
+    age[i++]=(char)shiftIn();
+    palSetPad(GPIOC, sel);
+    if (ti)
+      my_microsecond_delay(ti);
+  }
+  buf_index = 0;
+  buf_read = true;
+}
+#endif
+
 float SI4432_RSSI(uint32_t i, int s)
 {
   (void) i;
@@ -327,6 +354,15 @@ float SI4432_RSSI(uint32_t i, int s)
   } else
 #endif
 //START_PROFILE
+#ifdef __FAST_SWEEP__
+  if (buf_read) {
+    float dBm = ((float)((unsigned char)age[buf_index++]))/2 + SI4432_RSSI_correction;
+    if (buf_index ==POINTS_COUNT) {
+      buf_read = false;
+    }
+    return dBm;
+  }
+#endif
   SI4432_Sel = s;
   int stepdelay = actualStepDelay;
   if (SI4432_frequency_changed) {