update LED in readme

README.md

@@ -0,0 +1,85 @@
+# Wägetransmitter Modbus
+
+Ein Steuergerät zum Auslesen einer Wägezelle, angebunden über Modbus RTU.
+Die Wandlung des analogen Wägezellen-Signals basiert auf dem HX711 IC;
+auf einem Atmel AVR (ATmega328p) ist der Modbus-Slave implementiert.
+
+|![3D Model](board/pics/3d-board.png)|![eingebaut](board/pics/picture.png)|
+|:---:|:---:|
+
+### Schnittstellenparameter RS485/Modbus RTU
+
+| Parameter      | Wert   |
+|----------------|--------|
+| Baudrate       | 115200 |
+| Datenbits      | 8      |
+| Parität        | none   |
+| Stopbits       | 1      |
+| Modbus Adresse | 1      |
+
+Das Gerät stellt den 24-bit ADC Wert in 2er-Komplement Darstellung über zwei
+Holding-Register bereit. Somit ergibt sich ein 32-bit signed Integer Datentyp.
+
+| Register Adresse | Wert      |
+|------------------|-----------|
+| 0                | ADC[0:15] |
+| 1                | 8xADC[23],ADC[22:16]|
+
+#### Beispiel:
+Abfragen des Wertes mit dem Tool modpoll (https://www.modbusdriver.com/modpoll.html)
+```
+user@pc:~$ modpoll -b 115200 -p none -t4:int /dev/ttyUSB0
+modpoll 3.10 - FieldTalk(tm) Modbus(R) Master Simulator
+Copyright (c) 2002-2021 proconX Pty Ltd
+Visit https://www.modbusdriver.com for Modbus libraries and tools.
+
+Protocol configuration: Modbus RTU, FC3
+Slave configuration...: address = 1, start reference = 1, count = 1
+Communication.........: /dev/ttyUSB0, 115200, 8, 1, none, t/o 1.00 s, poll rate 100 ms
+Data type.............: 32-bit integer, output (holding) register table
+
+-- Polling slave... (Ctrl-C to stop)
+[1]: -242457
+-- Polling slave... (Ctrl-C to stop)
+[1]: -242440
+```
+
+### HX711
+
+Über den Jumper `JP1` kann eine Samplerate von 10Hz oder 80Hz gewählt werden.
+
+### LEDs
+
+| LED | Signal |
+|-----|--------|
+| D1  | Bus Error |
+| D2  | Bus Transmission       |
+| D3  | 5V Rail    |
+
+### Klemmenbelegung
+![fab](board/pics/board-fab.svg)
+
+#### J1
+| Klemme | Signal                         |
+|--------|--------------------------------|
+| 24V    | Spannungsversorgung 9V bis 24V |
+| GND    | Masse (Bus und Versorgung)     |
+| A+ / B-| RS485 Bus Leitungen            |
+| LEDn+  | Externe LED Anode (selbes Signal, wie intern)|
+| LEDn-  | Externe LED Kathode            |
+
+#### J4
+| Klemme | Signal                         |
+|--------|--------------------------------|
+| E+     | Spannungsversorgung Wägezelle  |
+| E-     | Masse                          |
+| INA-   | Messsignal 1                   |
+| INA+   | Messsignal 2                   |
+
+### Schaltplan
+![schematic](board/pics/schematic.svg)
+
+### Mechanische Dimensionen
+![dimensions](board/pics/board.svg)
+
+

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"
 
@@ -7,12 +8,9 @@
 
 uint16_t holdingRegisters[4];
 
-void timer0100us_start(void) {
+volatile uint32_t led_on_timer[3];
-	TCCR0B|=(1<<CS01); //prescaler 8
-	TIMSK0|=(1<<TOIE0);
-}
 
-//Return raw ADC data
+// 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;
     for(uint8_t i = 0; i < 24; i++){    //Start 24bit transmission
@@ -45,7 +43,7 @@ uint32_t HX711_get_data(uint8_t clk_PIN, uint8_t data_PIN, uint8_t gain_for_next
             extra_clk_pluses = 2;
             break;
         default:
-         extra_clk_pluses = 1;
+            extra_clk_pluses = 1;
     }
     for(uint8_t i = 0; i < extra_clk_pluses; i++){
         PORTB |= (1 << clk_PIN);    //set clock-PIN high
@@ -57,35 +55,34 @@ uint32_t HX711_get_data(uint8_t clk_PIN, uint8_t data_PIN, uint8_t gain_for_next
     /*  Convert 24bit Two's complement to 32bit Two's complement
         if MSB from 24Bit result is 1 aka negative*/
     if(data & (1L<<23)){
-            data |= 0xFFL << 24;
+        data |= 0xFFL << 24;
     }
     return data;
 }
 
 void modbusGet(void) {
-	if (modbusGetBusState() & (1<<ReceiveCompleted))
+    if (modbusGetBusState() & (1<<ReceiveCompleted))
-	{
+    {
-		switch(rxbuffer[1]) {
+        switch(rxbuffer[1]) {
-			case fcReadHoldingRegisters:
+            case fcReadHoldingRegisters:
-                PORTC ^= 1 << 1;
+                PORTC |= 1 << 0;
-//                _delay_ms(10);
+                led_on_timer[0]=1000;
-//                PORTC &= ~(1 << 1);
 
                 while(PINB & (1<<4)); // wait for data ready
 
                 uint32_t tmp = HX711_get_data(3, 4, 128); 
-                //int32_t tmp = -1000;
                 holdingRegisters[0] = tmp & 0xFFFF;
                 holdingRegisters[1] = (tmp>>16) & 0xFFFF;
-				modbusExchangeRegisters(holdingRegisters,0,4);
+                holdingRegisters[2] = led_on_timer[1];
-			break;
+                modbusExchangeRegisters(holdingRegisters,0,4);
-
+                break;
-            default: {
+            default:
-				modbusSendException(ecIllegalFunction);
+                PORTC |= 1 << 1;
-			}
+                led_on_timer[1]=1000;
-			break;
+                modbusSendException(ecIllegalFunction);
-		}
+                break;
-	}
+        }
+    }
 }
 
 int main(void){
@@ -93,19 +90,25 @@ int main(void){
     DDRB |= (1<<3);
 
     modbusSetAddress(1);
-	modbusInit();
+    modbusInit();
     sei();
 
-    timer0100us_start();
+    /* modbus tick timer */
+    TCCR0B|=(1<<CS01);
+    TIMSK0|=(1<<TOIE0);
 
     while(1){
         modbusGet();
-        //PORTC ^= 1 << 0;
-        //_delay_ms(100);
-        //PORTC &= ~(1 << 1);
     }
 }
 
 ISR(TIMER0_OVF_vect) { //this ISR is called 9765.625 times per second
-	modbusTickTimer();
+    modbusTickTimer();
+
+    for(uint8_t i=0; i<2; i++){
+        if(led_on_timer[i]>0)
+            led_on_timer[i]--;
+        else
+            PORTC &= ~(1<<i);
+    }
 }