1 files changed, 113 insertions, 0 deletions
diff --git a/Year_3/LSM/send_byte_buffer.c b/Year_3/LSM/send_byte_buffer.c
new file mode 100644
index 0000000..fe147b5
--- /dev/null
+++ b/Year_3/LSM/send_byte_buffer.c
@@ -0,0 +1,113 @@
+/* Run minicom -D /dev/ttyACM0 -b 9600 */
+
+#include "stm32_unict_lib.h"
+#include <stdio.h>
+
+#define MAX 128
+
+/* Slide 3/13 */
+
+struct t_tx_state {
+    uint8_t data;
+    uint8_t buffer[MAX];
+    int head, tail, data_count;
+    int bit_count;
+    int start;
+} tx_state;
+
+/*
+ * 9600 interruputs per seconds
+ * 84e6/9600 = 8750
+ */
+
+void
+init_periph()
+{
+    GPIO_init(GPIOA);
+    GPIO_config_output(GPIOA, 2);
+    GPIO_write(GPIOA, 2, 1);
+
+    TIM_init(TIM2);
+
+    TIM_config_timebase(TIM2, 1, 8750);
+
+    TIM_set(TIM2, 0);
+    TIM_on(TIM2);
+
+    TIM_enable_irq(TIM2, IRQ_UPDATE);
+
+    tx_state.start = 0;
+    tx_state.bit_count = 0;
+    tx_state.head = tx_state.tail = tx_state.data_count = 0;
+}
+
+void
+send_byte(uint8_t c)
+{
+    /* First wait the end of the trasmission */
+    while (tx_state.data_count == MAX) { }
+
+    tx_state.buffer[tx_state.head] = c;
+    tx_state.head = (tx_state.head + 1) % MAX;
+    tx_state.data_count++;
+    tx_state.start = 1;
+}
+int
+__io_putchar(int ch)
+{
+    send_byte(ch);
+    return 0;
+}
+
+int
+main()
+{
+    int i;
+    init_periph();
+
+    i = 0;
+    for (;;) {
+        printf("Hello world, %d\n\r", i++);
+        delay_ms(100);
+    }
+
+    return 0;
+}
+
+void
+TIM2_IRQHandler(void)
+{
+    if (TIM_update_check(TIM2)) {
+        if (tx_state.start) {
+            switch (tx_state.bit_count) {
+            case 0:
+                GPIO_write(GPIOA, 2, 0);
+                break;
+            case 9:
+            case 10:
+                GPIO_write(GPIOA, 2, 1);
+                break;
+            default:
+                /* Data bit */
+                GPIO_write(GPIOA, 2, tx_state.data & 1); // TX B0
+                tx_state.data >>= 1;
+            }
+            tx_state.bit_count++;
+
+            if (tx_state.bit_count == 11) {
+                --tx_state.data_count;
+
+                if (tx_state.data_count > 0) {
+                    tx_state.data = tx_state.buffer[tx_state.tail];
+                    tx_state.tail = (tx_state.tail + 1) % MAX;
+                } else {
+                    tx_state.start = 0;
+                }
+
+                tx_state.bit_count = 0;
+            }
+        }
+
+        TIM_update_clear(TIM2);
+    }
+}