1 files changed, 21 insertions, 94 deletions

diff --git a/02-usart/src/main.c b/02-usart/src/main.c
index b4f7dd7..b293202 100644
--- a/02-usart/src/main.c
+++ b/02-usart/src/main.c
@@ -1,4 +1,6 @@
 
+#include "isr_vector.h"
+#include "lib.h"
 #include "string.h"
 #include "mem.h"
 #include "dma.h"
@@ -8,117 +10,42 @@
 #include "gpio.h"
 #include "spin.h"
 #include "usart.h"
+#include "system.h"
 
-volatile uint32_t delay_amt = 20000000 / 4;
 
-int setup_usart2(uint32_t baud_rate)
-{
-  __IO gpio_port_t* port_a = enable_gpio(GPIO_PORT_A);
-  enable_hsi(&RCC, true);
-
-  // Turn on the clock for the USART2 peripheral
-  set_usart2_clock_src(&RCC, USART_CLK_SRC_HSI16);
-  set_usart2_clock_enabled(&RCC, true);
-
-  // Configure the I/O pins.  Will use PA2 as TX and PA15 as RX so setup for
-  // alternate function
-  set_gpio_pin_mode(port_a, PIN_2, MODE_ALTERNATE);
-  set_gpio_pin_mode(port_a, PIN_15, MODE_ALTERNATE);
-  set_gpio_alternate_function(port_a, PIN_2, AFN_7);
-  set_gpio_alternate_function(port_a, PIN_15, AFN_3);
-
-  // De-assert reset of USART2
-  RCC.apb1rst1_r &= ~BIT(17);
-
-  // Configure the USART
-  // disable USART first to allow setting of other control bits
-  // This also disables parity checking and enables 16 times oversampling
-
-  USART2.c_r1 = 0;
-  USART2.c_r2 = 0;
-  USART2.c_r3 = 0;
-
-  usart_set_divisor(&USART2, 16000000 / baud_rate);
-}
+#ifdef ARCH_STM32L4
 
-int enable_usart1(uint32_t baud_rate)
+/** Overrides the default systick irq handler. */
+void on_systick()
 {
-  /* Enable the GPIO bus. */
-  __IO gpio_port_t* port_b = enable_gpio(GPIO_PORT_B);
-
-  /* Enable the USART clock. */
-  RCC.apb2en_r |= BIT(14);
-
-  /* == Configure the IO Pins. == */
-
-  /* GPIO D5 (Port B pin 6) is USART1 Tx,
-   * GPIO D6 (Port B pin 7) is USART1 Rx. */
-  set_gpio_pin_mode(port_b, PIN_6, MODE_ALTERNATE);
-  set_gpio_pin_mode(port_b, PIN_7, MODE_ALTERNATE);
-
-  /* Set the GPIO pins to use the USART alternate function. */
-  set_gpio_alternate_function(port_b, PIN_6, AFN_7);
-  set_gpio_alternate_function(port_b, PIN_7, AFN_7);
+  static int is_on = 0;
 
-  RCC.apb2rst_r &= ~BIT(14); /* De-assert reset of USART1 */
-
-  uint32_t baud_rate_div = 80000000 / baud_rate;
-  USART1.c_r1 = 0;
-  USART1.c_r2 = 0;
-  USART1.c_r3 = 0;
-  USART1.br_r = baud_rate_div;
+  __IO gpio_port_t* port_b = enable_gpio(GPIO_PORT_B);
+  gpio_output_pin_t pin3 = set_gpio_pin_output(port_b, PIN_3);
 
-  USART1.c_r1 |= BIT(3) | BIT(2);
-  USART1.c_r1 |= BIT(0);
+  if (is_on) {
+    pin_off(pin3);
+  } else {
+    pin_on(pin3);
+  }
 
-  /* Enable the transmitter and the receiver. */
-  usart_set_enabled(&USART1, USART_ENABLE_TX);
-  enable_interrupts();
+  is_on = ! is_on;
 }
 
-#ifdef ARCH_STM32L4
-
 /* Main function. This gets executed from the interrupt vector defined above. */
 int main()
 {
-  /* Enable the GPIO port B. */
-
-  __IO gpio_port_t* port_b = enable_gpio(GPIO_PORT_B);
-  gpio_output_pin_t pin3 = set_gpio_pin_output(port_b, PIN_3);
-  gpio_output_pin_t pin1 = set_gpio_pin_output(port_b, PIN_1);
-
   /* Enable a higher clock frequency. */
   set_system_clock_MHz(80);
 
-  setup_usart2(115200);
-
-
-  char* into = (char*) (SRAM1_BASE + 50);
-  const char* hello = "Hello, Chester Cheeto!\r\n";
-  int len = strlen(hello);
-  memcpy(into, hello, len + 1);
-
-  usart_enable_dma(&USART2, USART_ENABLE_TX);
-  usart_set_enabled(&USART2, USART_ENABLE_TX | USART_ENABLE_RX);
-
-  pin_on(pin3);
-
-  RCC.ahb1en_bf.dma1en = 1; /* Enable DMA1 Clock. */
-  DMA1.csel_bf.c7s = 0x2; /* Select USART2_TX for the sel. */
-  DMA1.channel_config[6].cc_r = 0;
-  DMA1.channel_config[6].cc_bf.dir = READ_FROM_MEMORY;
-  DMA1.channel_config[6].cc_bf.minc = 1;
-  DMA1.channel_config[6].cc_bf.pl = DMA_PRIORITY_LEVEL_VERY_HIGH;
-  DMA1.channel_config[6].cndt_bf.ndt = len;
-  DMA1.channel_config[6].cpa_r = ptr2reg(&USART2.td_r);
-  DMA1.channel_config[6].cma_r = ptr2reg(into);
+  /* Set the countdown to start from 1,000,0000. */
+  SCB.strv_r = 10000000;
 
-  USART2.ic_bf.tccf = 1;
-  DMA1.channel_config[6].cc_bf.en = 1;
+  /* Enable interrupts. */
+  SCB.stcs_bf.tickint = 1;
 
-  pin_on(pin3);
-  // usart_transmit_str_sync(&USART2, into);
-  for(;;);
+  /* Start the systick. */
+  SCB.stcs_bf.enable = 1;
 }
 
 #endif