From 906405bab5c8b1a445e5d0408d38dddb1f504747 Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Mon, 10 Jan 2022 11:04:30 +0100
Subject: lsm: sources send bytes on uart

---
 Year_3/LSM/send_byte.c        | 100 +++++++++++++++++++++++++++++++++++++
 Year_3/LSM/send_byte_buffer.c | 113 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 213 insertions(+)
 create mode 100644 Year_3/LSM/send_byte.c
 create mode 100644 Year_3/LSM/send_byte_buffer.c

diff --git a/Year_3/LSM/send_byte.c b/Year_3/LSM/send_byte.c
new file mode 100644
index 0000000..21e9c90
--- /dev/null
+++ b/Year_3/LSM/send_byte.c
@@ -0,0 +1,100 @@
+/* Run minicom -D /dev/ttyACM0 -b 9600 */
+
+#include "stm32_unict_lib.h"
+#include <stdio.h>
+
+/* Slide 3/13 */
+
+struct t_tx_state {
+    uint8_t data;
+    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;
+}
+
+void
+send_byte(uint8_t c)
+{
+    /* First wait the end of the trasmission */
+    while (tx_state.start == 1) { }
+
+    tx_state.data = c;
+    tx_state.start = 1;
+    tx_state.bit_count = 0;
+}
+
+/*int
+__io_putchar(int ch)
+{
+	send_byte(ch);
+	return 0;
+}*/
+
+int
+main()
+{
+    init_periph();
+
+    for (;;) {
+        /* Using a `printf()` here means you must overwrite the `__io_putchar()` in `console.c`. */
+        // printf("Hello world\n\r");
+
+        send_byte('A');
+        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.start = 0;
+            }
+        }
+
+        TIM_update_clear(TIM2);
+    }
+}
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);
+    }
+}
-- 
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