From 4e0b81034644f7f2332c532ecce5fb31590545d6 Mon Sep 17 00:00:00 2001
From: "Sebastian H. Gabrielli" <gabrielli@sebaweb.no>
Date: Wed, 20 Mar 2024 13:00:40 +0100
Subject: [PATCH] Functioning I2C slave data receive

The slave now receives and prints data successfully.
---
 prosjekt.X/i2c.c                        | 63 ++++++++++++++++++++++---
 prosjekt.X/i2c.h                        |  2 +
 prosjekt.X/main.c                       |  8 +++-
 prosjekt.X/nbproject/configurations.xml |  3 ++
 4 files changed, 67 insertions(+), 9 deletions(-)

diff --git a/prosjekt.X/i2c.c b/prosjekt.X/i2c.c
index 6474273..7b0eddc 100644
--- a/prosjekt.X/i2c.c
+++ b/prosjekt.X/i2c.c
@@ -1,6 +1,15 @@
 #include "i2c.h"
 
+// Heavily inspired by: https://github.com/microchip-pic-avr-examples/avr128db48-bare-metal-twi-mplab/blob/master/twi-client.X/peripherals/TWI/TWI_client.c
+
 void init_i2c(void) {
+  // Pin setup
+  PORTA.DIRSET = PIN2_bm | PIN3_bm;
+  PORTA.PINCTRLUPD = PIN2_bm | PIN3_bm;
+    
+  // Enable operating in debug
+  TWI0.DBGCTRL = TWI_DBGRUN_bm;
+    
   // Initialize the control A register
   TWI0.CTRLA = TWI_INPUTLVL_I2C_gc    // I2C voltage transition level
                | TWI_SDASETUP_4CYC_gc // Four clock cycles setup time
@@ -13,20 +22,60 @@ void init_i2c(void) {
 
   // Enable acting as a slave
   TWI0.SCTRLA = TWI_DIEN_bm     // Enable data interrupt
+                | TWI_APIEN_bm  // Enable more interrupts
                 | TWI_PIEN_bm   // Enable stop flag interrupt
-                | TWI_SMEN_bm   // Enable smart mode
+                | PIN2_bm       // Respond to all TWI addresses
                 | TWI_ENABLE_bm // Enable acting as a slave
       ;
 }
 
 // TODO: Figure out which interrupt does what
 
-// Interrupt vector
-ISR(TWI0_TWIS_vect) {
-    asm('nop');
+void i2c_write_handler(uint8_t data) {
+    printf("%u\n", data);
 }
 
-// Interrupt vector
-ISR(TWI0_TWIM_vect) {
-    asm('nop');
+void i2c_read_handler() {
+    printf("Master wanted to read.\n");
+}
+
+void i2c_stop_handler() {
+    printf("Stop, I guess\n");
+}
+
+// Address received
+ISR(TWI0_TWIS_vect) {
+    // Check for the data interrupt flag
+    if (TWI0.SSTATUS & TWI_DIF_bm) {
+        uint8_t data = 0;
+        
+        if ( ((TWI0.SSTATUS & TWI_DIR_bm) >> TWI_DIR_bp) == 0 ) {
+            // Data write Master -> Slave
+            data = TWI0.SDATA;
+            
+            // Send the data to the write handler
+            i2c_write_handler(data);
+        } else {
+            // Data read Master <- Slave
+            i2c_read_handler();
+            data = TWI0.SDATA;
+        }
+        
+        // Acknowledge having received
+        TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
+    }
+    
+    // Check for address match or STOP
+    if (TWI0.SSTATUS & TWI_APIF_bm) {
+        
+        if (TWI0.SSTATUS & TWI_AP_ADR_gc) {
+            // Address match, just send ack
+            TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
+        } else {
+            // STOP condition received
+            i2c_stop_handler();
+            // Send ACK
+            TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
+        }
+    }
 }
\ No newline at end of file
diff --git a/prosjekt.X/i2c.h b/prosjekt.X/i2c.h
index 7330fd8..0e8f64f 100644
--- a/prosjekt.X/i2c.h
+++ b/prosjekt.X/i2c.h
@@ -15,6 +15,8 @@ extern "C" {
 // Include the IO for I2C
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include "uart.h"
+#include <util/twi.h>
 
 // Initialize the I2C bus
 void init_i2c(void);
diff --git a/prosjekt.X/main.c b/prosjekt.X/main.c
index b42afa9..25f1319 100644
--- a/prosjekt.X/main.c
+++ b/prosjekt.X/main.c
@@ -10,14 +10,18 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include "uart.h"
+#include "i2c.h"
 #include <util/delay.h>
 
-int main() {
+int main() {    
     init_uart((uint16_t)9600);
+    init_i2c();
     stdout = &USART_stream;
+    
+    sei();
 
     while (1) {
-        printf("Hello, world!\n");
+        printf("\n");
         _delay_ms(500);
     }
 }
\ No newline at end of file
diff --git a/prosjekt.X/nbproject/configurations.xml b/prosjekt.X/nbproject/configurations.xml
index 89c9ad4..528acb5 100644
--- a/prosjekt.X/nbproject/configurations.xml
+++ b/prosjekt.X/nbproject/configurations.xml
@@ -171,6 +171,9 @@
         <property key="user-pack-device-support" value=""/>
         <property key="wpo-lto" value="false"/>
       </XC8-config-global>
+      <nEdbgTool>
+        <property key="debugoptions.useswbreakpoints" value="true"/>
+      </nEdbgTool>
     </conf>
   </confs>
 </configurationDescriptor>