change led behavior

code/main.c

@@ -1,5 +1,6 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include <stdint.h>
 #include <util/delay.h>
 #include "modbus.h"
 
@@ -7,6 +8,8 @@
 
 uint16_t holdingRegisters[4];
 
+volatile uint32_t led_on_timer[3];
+
 // return raw ADC data
 uint32_t HX711_get_data(uint8_t clk_PIN, uint8_t data_PIN, uint8_t gain_for_next_conv){
     uint32_t data = 0;
@@ -62,16 +65,20 @@ void modbusGet(void) {
     {
         switch(rxbuffer[1]) {
             case fcReadHoldingRegisters:
-                PORTC ^= 1 << 1;      // toggle led
+                PORTC |= 1 << 0;
+                led_on_timer[0]=1000;
 
                 while(PINB & (1<<4)); // wait for data ready
 
                 uint32_t tmp = HX711_get_data(3, 4, 128); 
                 holdingRegisters[0] = tmp & 0xFFFF;
                 holdingRegisters[1] = (tmp>>16) & 0xFFFF;
+                holdingRegisters[2] = led_on_timer[1];
                 modbusExchangeRegisters(holdingRegisters,0,4);
                 break;
             default:
+                PORTC |= 1 << 1;
+                led_on_timer[1]=1000;
                 modbusSendException(ecIllegalFunction);
                 break;
         }
@@ -97,4 +104,11 @@ int main(void){
 
 ISR(TIMER0_OVF_vect) { //this ISR is called 9765.625 times per second
     modbusTickTimer();
+
+    for(uint8_t i=0; i<2; i++){
+        if(led_on_timer[i]>0)
+            led_on_timer[i]--;
+        else
+            PORTC &= ~(1<<i);
+    }
 }