option to boot at 4MHz with no USB

targets/stm32l432/src/device.c

@@ -108,7 +108,9 @@ void device_reboot()
 void device_init()
 {
     hw_init();
+    #ifndef IS_BOOTLOADER
         nfc_init();
+    #endif
     LL_GPIO_SetPinMode(SOLO_BUTTON_PORT,SOLO_BUTTON_PIN,LL_GPIO_MODE_INPUT);
     LL_GPIO_SetPinPull(SOLO_BUTTON_PORT,SOLO_BUTTON_PIN,LL_GPIO_PULL_UP);
 
@@ -395,7 +397,9 @@ void device_manage()
         }
     }
 #endif
+#ifndef IS_BOOTLOADER
     nfc_loop();
+#endif
 }
 
 static int handle_packets()

targets/stm32l432/src/init.c

@@ -122,12 +122,14 @@ static void LL_Init(void)
     NVIC_SetPriority(SysTick_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),0, 0));
 
 }
-
+static int NFC = 0;
 /**
   * @brief System Clock Configuration
   * @retval None
   */
 void SystemClock_Config(void)
+{
+    if (!NFC)
     {
 
           LL_FLASH_SetLatency(LL_FLASH_LATENCY_2);
@@ -209,8 +211,68 @@ void SystemClock_Config(void)
           /* SysTick_IRQn interrupt configuration */
           NVIC_SetPriority(SysTick_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),0, 0));
     }
+    else
+    {
+        LL_FLASH_SetLatency(LL_FLASH_LATENCY_0);
+
+        if(LL_FLASH_GetLatency() != LL_FLASH_LATENCY_0)
+        {
+        Error_Handler();
+        }
+        LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
+
+        LL_RCC_LSI_Enable();
+
+         /* Wait till LSI is ready */
+        while(LL_RCC_LSI_IsReady() != 1)
+        {
+
+        }
+        LL_RCC_MSI_Enable();
+
+         /* Wait till MSI is ready */
+        while(LL_RCC_MSI_IsReady() != 1)
+        {
+
+        }
+        LL_RCC_MSI_EnableRangeSelection();
+
+        LL_RCC_MSI_SetRange(LL_RCC_MSIRANGE_6);
+
+        LL_RCC_MSI_SetCalibTrimming(0);
+
+        LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_MSI);
+
+         /* Wait till System clock is ready */
+        while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_MSI)
+        {
+
+        }
+        LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
+
+        LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_1);
+
+        LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);
+
+        LL_Init1msTick(4000000);
+
+        LL_SYSTICK_SetClkSource(LL_SYSTICK_CLKSOURCE_HCLK);
+
+        LL_SetSystemCoreClock(4000000);
+
+        LL_RCC_SetUSARTClockSource(LL_RCC_USART1_CLKSOURCE_PCLK2);
+
+        LL_RCC_SetRNGClockSource(LL_RCC_RNG_CLKSOURCE_MSI);
+
+        /* SysTick_IRQn interrupt configuration */
+        NVIC_SetPriority(SysTick_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),0, 0));
+    }
+
+}
 
 void usb_init()
+{
+    if (!NFC)
     {
         // enable USB power
         SET_BIT(PWR->CR2, PWR_CR2_USV);
@@ -235,11 +297,13 @@ void usb_init()
 
         USBD_Start(&Solo_USBD_Device);
     }
+}
 
 /* TIM2 init function */
 static void MX_TIM2_Init(void)
 {
-
+    // if(!NFC)
+    {
         LL_TIM_InitTypeDef TIM_InitStruct;
         LL_TIM_OC_InitTypeDef TIM_OC_InitStruct;
 
@@ -305,6 +369,7 @@ static void MX_TIM2_Init(void)
         LL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
         LL_TIM_EnableCounter(TIM2);
+    }
 
 }
 
@@ -369,7 +434,11 @@ static void MX_TIM6_Init(void)
 
     // 48 MHz sys clock --> 6 MHz timer clock
     // 48 MHz / 48000 == 1000 Hz
+    if (!NFC)
         TIM_InitStruct.Prescaler = 48000;
+    else
+        TIM_InitStruct.Prescaler = 4000;
+
     TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;
     TIM_InitStruct.Autoreload = 90;
     LL_TIM_Init(TIM6, &TIM_InitStruct);
@@ -458,7 +527,10 @@ static void MX_SPI1_Init(void)
     SPI_InitStruct.ClockPolarity = LL_SPI_POLARITY_LOW;
     SPI_InitStruct.ClockPhase = LL_SPI_PHASE_2EDGE;
     SPI_InitStruct.NSS = LL_SPI_NSS_SOFT;
+    if (!NFC)
         SPI_InitStruct.BaudRate = LL_SPI_BAUDRATEPRESCALER_DIV64;
+    else
+        SPI_InitStruct.BaudRate = LL_SPI_BAUDRATEPRESCALER_DIV8;
     SPI_InitStruct.BitOrder = LL_SPI_MSB_FIRST;
     SPI_InitStruct.CRCCalculation = LL_SPI_CRCCALCULATION_DISABLE;
     SPI_InitStruct.CRCPoly = 7;

targets/stm32l432/src/redirect.c

@@ -37,15 +37,18 @@ void _putchar(char c)
     LL_USART_TransmitData8(DEBUG_UART,c);
 #endif
 }
-
+static int NFC = 0;
 
 
 int _write (int fd, const void *buf, long int len)
 {
     uint8_t * data = (uint8_t *) buf;
 
+    if (!NFC)
+    {
         // Send out USB serial
         CDC_Transmit_FS(data, len);
+    }
 
     // Send out UART serial
     while(len--)