Add low output start burst

main.c

@@ -907,6 +907,7 @@ config_t config = {
   .cor_am = -14,
   .cor_wfm = -17,
   .cor_nfm = -17,
+  .sweep_voltage = 3.3,
 };
 
 //properties_t current_props;
@@ -2348,6 +2349,7 @@ static const VNAShellCommand commands[] =
     {"time"        , cmd_time        , 0},
 #endif
     {"dac"         , cmd_dac         , 0},
+    {"sweep_voltage",cmd_sweep_voltage,0},
     {"saveconfig"  , cmd_saveconfig  , 0},
     {"clearconfig" , cmd_clearconfig , 0},
     {"data"        , cmd_data        , CMD_WAIT_MUTEX},

nanovna.h

@@ -527,6 +527,7 @@ typedef struct config {
   int8_t    cor_am;
   int8_t    cor_wfm;
   int8_t    cor_nfm;
+  float sweep_voltage;
   uint32_t    dummy;
 //  uint8_t _reserved[22];
   freq_t checksum;

plot.c

@@ -119,7 +119,7 @@ float2int(float v)
 
 void update_grid(void)
 {
-  freq_t gdigit = 100000000;
+  freq_t gdigit = 1000000000;
   freq_t fstart = get_sweep_frequency(ST_START);
   freq_t fspan  = get_sweep_frequency(ST_SPAN);
   freq_t grid;

sa_cmd.c

@@ -246,6 +246,17 @@ VNA_SHELL_FUNCTION(cmd_deviceid)
   }
 }
 
+VNA_SHELL_FUNCTION(cmd_sweep_voltage)
+{
+  float value;
+  if (argc != 1) {
+    shell_printf("usage: sweep_voltage {value(0-3.3)}\r\n"\
+                 "current value: %f\r\n", config.sweep_voltage);
+    return;
+  }
+  value = my_atof(argv[0]);
+  config.sweep_voltage = value;
+}
 
 VNA_SHELL_FUNCTION(cmd_rbw)
 {

sa_core.c

@@ -1698,6 +1698,10 @@ pureRSSI_t perform(bool break_on_operation, int i, freq_t f, int tracking)     /
   }
 
   if (setting.mode == M_GENLOW && ( setting.frequency_step != 0 || setting.level_sweep != 0.0 || i == 0)) {// if in low output mode and level sweep or frequency weep is active or at start of sweep
+    if (i == 0)
+      set_switch_transmit();
+    else
+      set_switch_off();
     float ls=setting.level_sweep;                                           // calculate and set the output level
     if (ls > 0)
       ls += 0.5;
@@ -2171,7 +2175,7 @@ sweep_again:                                // stay in sweep loop when output mo
       return false;
     }
 
-    dacPutChannelX(&DACD2, 0, i*14);        // Output sweep voltage
+    dacPutChannelX(&DACD2, 0, (((float)i)*config.sweep_voltage)*4.279);        // Output sweep voltage  4095 -> 3.3 Volt
 
     // ----------------------- in loop AGC ---------------------------------