interrupts working now with timer

1 files changed, 18 insertions, 13 deletions

diff --git a/fw/ds18b20.c b/fw/ds18b20.c
index 0b57732..74ac1be 100644
--- a/fw/ds18b20.c
+++ b/fw/ds18b20.c
@@ -30,22 +30,26 @@ static const uint8_t frac_tens[16] = {0,0,1,1,2,3,3,4,5,5,6,6,7,8,8,9};
 static const uint8_t frac_hund[16] = {0,6,2,8,5,1,7,4,0,6,2,8,5,1,7,3};
 
 /*
- * Timer0 delay.  OPTION_REG 0x07: T0CS=0 (Fosc/4), PSA=0, PS=111 (1:256).
+ * Timer0 interrupt-driven delay.  OPTION_REG, T0IF, T0IE, GIE from pic16f84a.h.
+ * OPTION_REG 0x07: T0CS=0 (Fosc/4), PSA=0, PS=111 (1:256).
  * At 50 MHz: overflow every 256*256 / (50M/4) = 5.24 ms.
  * 143 overflows ≈ 750 ms.
  */
-#define STATUS_RP0    0x20
-#define T0IF          0x04
+#define OVF_750MS  143
 
-static void wait_overflows(uint8_t n) {
-    INTCON &= ~T0IF;
-    while (n--) {
-        while (!(INTCON & T0IF));
-        INTCON &= ~T0IF;
+static volatile uint8_t ovf_count = 0;
+
+void isr(void) __interrupt(0) {
+    if (INTCON & 0x04) {        /* T0IF = bit 2 */
+        ovf_count++;
+        INTCON &= ~(uint8_t)0x04;
     }
 }
 
-static void delay_750ms(void) { wait_overflows(143); }
+static void delay_750ms(void) {
+    ovf_count = 0;
+    while (ovf_count < OVF_750MS);
+}
 
 static void uart_send(uint8_t b) {
     while (UART_STATUS & 0x01);
@@ -88,10 +92,11 @@ void main(void) {
     uint8_t lo, hi, sign, temp_int, frac;
     uint8_t i;
 
-    /* Configure Timer0: bank 1, OPTION_REG = 0x07 (Fosc/4, prescaler 1:256) */
-    STATUS |= STATUS_RP0;
-    TMR0 = 0x07;
-    STATUS &= ~STATUS_RP0;
+    /* T0CS=0 (Fosc/4), PSA=0, PS=111 (1:256 prescaler) */
+    OPTION_REG = 0x07;
+
+    TMR0 = 0;
+    INTCON = 0xa0;    /* T0IE | GIE */    /* enable Timer0 overflow interrupt */
 
     uart_puts("\x1B[2J\x1B[H");
     uart_puts("DS18B20 Temperature\r\n");