diff --git a/Makefile b/Makefile
index cb3b96b..dd4f8f3 100644
--- a/Makefile
+++ b/Makefile
@@ -12,9 +12,9 @@ TARGET=F303
 # Compiler options here.
 ifeq ($(USE_OPT),)
  ifeq ($(TARGET),F303)
-USE_OPT = -O2 -fno-inline-small-functions -ggdb -fomit-frame-pointer -falign-functions=16 --specs=nano.specs -fstack-usage -std=c11
+USE_OPT = -Og -fno-inline-small-functions -ggdb -fomit-frame-pointer -falign-functions=16 --specs=nano.specs -fstack-usage -std=c11
  else
-USE_OPT = -O2 -fno-inline-small-functions -ggdb -fomit-frame-pointer -falign-functions=16 --specs=nano.specs -fstack-usage -std=c11
+USE_OPT = -Og -fno-inline-small-functions -ggdb -fomit-frame-pointer -falign-functions=16 --specs=nano.specs -fstack-usage -std=c11
  endif
 endif
 
diff --git a/NANOVNA_STM32_F303/board.h b/NANOVNA_STM32_F303/board.h
index 8bfa51d..95c5af2 100644
--- a/NANOVNA_STM32_F303/board.h
+++ b/NANOVNA_STM32_F303/board.h
@@ -270,7 +270,7 @@
                                      PIN_OTYPE_PUSHPULL(GPIOB_I2S2_MOSI))
 #define VAL_GPIOB_OSPEEDR           (PIN_PUPDR_FLOATING(GPIOB_XN) | \
                                      PIN_PUPDR_FLOATING(GPIOB_YN) | \
-                                     PIN_OSPEED_100M(GPIOB_RX_SEL) |          \
+                                     PIN_OSPEED_2M(GPIOB_RX_SEL) |          \
                                      PIN_OSPEED_100M(3) | \
                                      PIN_OSPEED_100M(4) |          \
                                      PIN_OSPEED_100M(5) |          \
@@ -278,7 +278,7 @@
                                      PIN_OSPEED_100M(7) |          \
                                      PIN_OSPEED_100M(GPIOB_I2C1_SCL) | \
                                      PIN_OSPEED_100M(GPIOB_I2C1_SDA) | \
-                                     PIN_OSPEED_100M(GPIOB_LO_SEL) |         \
+                                     PIN_OSPEED_2M(GPIOB_LO_SEL) |         \
                                      PIN_OSPEED_100M(11) |         \
                                      PIN_OSPEED_100M(GPIOB_I2S2_WCLK) | \
                                      PIN_OSPEED_100M(GPIOB_I2S2_BCLK) | \
diff --git a/main.c b/main.c
index f552c9f..782ef75 100644
--- a/main.c
+++ b/main.c
@@ -1,6 +1,5 @@
 /*
  *
- * This is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 3, or (at your option)
  * any later version.
@@ -124,7 +123,7 @@ extern int dirty;
 
 bool completed = false;
 
-static THD_WORKING_AREA(waThread1, 1024);
+static THD_WORKING_AREA(waThread1, 1124);
 static THD_FUNCTION(Thread1, arg)
 {
   (void)arg;
@@ -2352,7 +2351,8 @@ static const VNAShellCommand commands[] =
  #ifdef ENABLE_THREADS_COMMAND
      {"threads"     , cmd_threads     , 0},
  #endif
-    { "y", cmd_y,    0 },
+     { "y", cmd_y,    CMD_WAIT_MUTEX },
+     { "z", cmd_z,    CMD_WAIT_MUTEX },
    { "i", cmd_i,	0 },
    { "v", cmd_v,	0 },
    { "a", cmd_a,	0 },
diff --git a/sa_cmd.c b/sa_cmd.c
index 06eadee..f885280 100644
--- a/sa_cmd.c
+++ b/sa_cmd.c
@@ -301,6 +301,31 @@ VNA_SHELL_FUNCTION(cmd_y)
   }
 }
 
+VNA_SHELL_FUNCTION(cmd_z)
+{
+  static const char cmd_z_list[] = "t|r|i";
+  if (argc != 1) {
+    shell_printf("usage: z %s\r\n", cmd_z_list);
+    return;
+  }
+  if (argc == 1) {
+    SI4432_Sel = VFO;
+    int type = get_str_index(argv[0], cmd_z_list);
+    switch(type) {
+    case 0:
+      SI4432_Transmit(3);
+      break;
+    case 1:
+      SI4432_Receive();
+      break;
+    case 2:
+      SI4432_Reset();
+      break;
+    }
+  }
+}
+
+
 VNA_SHELL_FUNCTION(cmd_selftest)
 {
   if (argc < 1 || argc > 2) {
diff --git a/si4432.c b/si4432.c
index 96615f2..9f500bf 100644
--- a/si4432.c
+++ b/si4432.c
@@ -42,7 +42,8 @@
 // Hardware or software SPI use
 #ifdef USE_HARDWARE_SPI_MODE
 #define SI4432_SPI         SPI1
-#define SI4432_SPI_SPEED   SPI_BR_DIV8
+//#define SI4432_SPI_SPEED   SPI_BR_DIV8
+#define SI4432_SPI_SPEED   SPI_BR_DIV64
 static uint32_t old_spi_settings;
 #else
 static uint32_t old_port_moder;
@@ -88,8 +89,8 @@ void start_SI4432_SPI_mode(void){
   new_port_moder|= PIN_MODE_OUTPUT(GPIOB_SPI_SCLK)|PIN_MODE_INPUT(GPIOB_SPI_MISO)|PIN_MODE_OUTPUT(GPIOB_SPI_MOSI);
   GPIOB->MODER = new_port_moder;
   // Pull down SPI
-  SPI_SDI_LOW;
-  SPI_CLK_LOW;
+  SPI1_SDI_LOW;
+  SPI1_CLK_LOW;
 #endif
 }