From eb8643ddbef43547eb7bfe58789a3908926c7258 Mon Sep 17 00:00:00 2001
From: Vaino Kauppila <vaino@vke.fi>
Date: Sun, 19 Apr 2026 12:32:58 +0300
Subject: refactor dir structure, add fib.c

---
 fw/blink.c     | 35 ++++++++++++++++++++++++
 fw/fib.c       | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fw/test_uart.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 188 insertions(+)
 create mode 100644 fw/blink.c
 create mode 100644 fw/fib.c
 create mode 100644 fw/test_uart.c

(limited to 'fw')

diff --git a/fw/blink.c b/fw/blink.c
new file mode 100644
index 0000000..6789b0a
--- /dev/null
+++ b/fw/blink.c
@@ -0,0 +1,35 @@
+#include <pic16f84a.h>
+
+typedef unsigned char uint8_t;
+
+// Global volatile so sdcc cannot optimise the delay loops away.
+static volatile uint8_t _d0, _d1, _d2;
+
+// Busy-wait ~500 ms at 50 MHz.
+// 200 × 256 × 256 = 13 107 200 inner iterations.
+// Each iteration ≈ 3 uint8_t instructions × 20 ns = 60 ns.
+// Total ≈ 786 ms  (tune outer count _d0 < N to taste).
+static void delay(void) {
+    _d0 = 0;
+    do {
+        _d1 = 0;
+        do {
+            _d2 = 0;
+            do { _d2++; } while (_d2 != 0);
+        } while (++_d1 != 30);
+        _d0++;
+    } while (_d0 != 116);
+}
+
+void main(void) {
+    // port_b(0) drives activity_led at E8 on the Tang Primer 25K.
+    // port_a(0) drives led at L6.  Both ports are always outputs in this CPU.
+    while (1) {
+        PORTB = 0x01;   // activity_led (E8) on
+        PORTA = 0x01;   // led (L6) on
+        delay();
+        PORTB = 0x00;   // activity_led (E8) off
+        PORTA = 0x00;   // led (L6) off
+        delay();
+    }
+}
diff --git a/fw/fib.c b/fw/fib.c
new file mode 100644
index 0000000..2ba9535
--- /dev/null
+++ b/fw/fib.c
@@ -0,0 +1,84 @@
+#include <pic16f84a.h>
+
+typedef unsigned char uint8_t;
+
+__sfr __at(0x70) UART_TX;
+__sfr __at(0x71) UART_RX;
+__sfr __at(0x72) UART_STATUS;
+
+static volatile uint8_t _d0, _d1, _d2;
+
+// Custom delay to make the output readable at 50MHz
+static void delay(void) {
+    _d0 = 0;
+    do {
+        _d1 = 0;
+        do {
+            _d2 = 0;
+            do { _d2++; } while (_d2 != 0);
+        } while (++_d1 != 50); // Increased for 50MHz visibility
+        _d0++;
+    } while (_d0 != 20);
+}
+
+static void uart_send(uint8_t byte) {
+    while (UART_STATUS & 0x01); 
+    UART_TX = byte;
+}
+
+static void uart_puts_rom(const char *s) {
+    while (*s) {
+        uart_send((uint8_t)*s);
+        s++;
+    }
+}
+
+// Simple BCD printer for 8-bit numbers
+void print_uint8(uint8_t v) {
+    uint8_t started = 0;
+    
+    // Hundreds
+    if (v >= 200) { uart_send('2'); v -= 200; started = 1; }
+    else if (v >= 100) { uart_send('1'); v -= 100; started = 1; }
+
+    // Tens
+    uint8_t tens = '0';
+    while (v >= 10) { v -= 10; tens++; }
+    if (started || tens != '0') { uart_send(tens); }
+
+    // Units
+    uart_send(v + '0');
+}
+
+void main(void) {
+    uint8_t a, b, next;
+    
+    uart_puts_rom("\x1B[2J\x1B[H"); // Clear screen, Home cursor
+    uart_puts_rom("PIC16F84A @ 50MHz Fibonacci\r\n");
+    uart_puts_rom("---------------------------\r\n");
+
+    while (1) {
+        a = 0;
+        b = 1;
+
+        while (a <= 233) { // Max 8-bit Fib is 233
+            print_uint8(a);
+            uart_puts_rom(", ");
+
+            next = a + b;
+            a = b;
+            b = next;
+
+            delay();
+            
+            // Break before overflow
+            if (a == 233) {
+                print_uint8(a);
+                break;
+            }
+        }
+        
+        uart_puts_rom("\r\nRestarting...\r\n");
+        delay();
+    }
+}
diff --git a/fw/test_uart.c b/fw/test_uart.c
new file mode 100644
index 0000000..4e18dc5
--- /dev/null
+++ b/fw/test_uart.c
@@ -0,0 +1,69 @@
+#include <pic16f84a.h>
+
+typedef unsigned char uint8_t;
+
+__sfr __at(0x70) UART_TX;
+__sfr __at(0x71) UART_RX;
+__sfr __at(0x72) UART_STATUS;
+
+static volatile uint8_t _d0, _d1, _d2;
+static uint8_t counter;
+
+static void delay(void) {
+    _d0 = 0;
+    do {
+        _d1 = 0;
+        do {
+            _d2 = 0;
+            do { _d2++; } while (_d2 != 0);
+        } while (++_d1 != 30);
+        _d0++;
+    } while (_d0 != 10);
+}
+
+static void uart_send(uint8_t byte) {
+    while (UART_STATUS & 0x01); 
+    UART_TX = byte;
+}
+
+// Keep this ONLY for literal strings (ROM)
+static void uart_puts_rom(const char *s) {
+    while (*s) {
+        uart_send((uint8_t)*s);
+        s++;
+    }
+}
+
+void main(void) {
+    counter = 0;
+    uart_puts_rom("counter\r\n");
+
+    while (1) {
+        uint8_t v = counter;
+        uint8_t started = 0;
+
+
+        uart_puts_rom("\r");
+		uart_puts_rom("\x1B[K");        
+
+        uart_send('C');
+        uart_send(':');
+
+        // Hundreds
+        if (v >= 200) { uart_send('2'); v -= 200; started = 1; }
+        else if (v >= 100) { uart_send('1'); v -= 100; started = 1; }
+
+        // Tens
+        {
+            uint8_t tens = '0';
+            while (v >= 10) { v -= 10; tens++; }
+            if (started || tens != '0') { uart_send(tens); }
+        }
+
+        // Units (always)
+        uart_send(v + '0');
+
+        counter++;
+        delay();
+    }
+}
-- 
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