varpa: initial public commit

1 files changed, 114 insertions, 0 deletions

diff --git a/firmware/src/peripheral/twi.c b/firmware/src/peripheral/twi.c
new file mode 100644
index 0000000..671490b
--- /dev/null
+++ b/firmware/src/peripheral/twi.c
@@ -0,0 +1,114 @@
+/**
+ * 
+ * Author: Dylan Muller
+ * Copyright (c) 2025 
+ * All rights reserved.
+ * 
+ * - Commercial/IP use prohibited.
+ * - Attribution required.
+ * See License.txt
+ *
+ */
+
+#include "setup.h"
+
+#include "peripheral/twi.h"
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <util/twi.h>
+
+#define TWBR_VALUE ((F_CPU/TWI_FREQUENCY - 16) / (2 * TWI_PRESCALER))
+
+static uint8_t twi_address;
+static uint8_t* twi_data;
+static size_t twi_index;
+static size_t twi_len;
+
+void twi_init(void)
+{
+    TWBR = TWBR_VALUE;
+    TWSR = (TWPS1_VALUE << TWPS1) | (TWPS0_VALUE << TWPS0);
+    
+    TWCR = (1 << TWINT) | (1 << TWEN);
+}
+
+bool twi_busy(void)
+{
+    return TWCR & (1<<TWIE);
+}
+
+void twi_flush(void)
+{
+    while(TWCR & (1<<TWIE));
+}
+
+void twi_start(
+    uint8_t address,
+    uint8_t *data,
+    size_t len
+)
+{
+    twi_flush();
+    
+    twi_address = address;
+    twi_data = data;
+    twi_len = len;
+    
+    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN) | (1 << TWIE);
+}
+
+ISR(TWI_vect)
+{
+    switch(TW_STATUS)
+    {
+        case TW_START:
+        case TW_REP_START:
+            twi_index = 0;
+            TWDR = twi_address;
+            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE);
+            break;
+        
+        case TW_MT_SLA_ACK:
+        case TW_MT_DATA_ACK:
+            if(twi_index < twi_len)
+            {
+                TWDR = twi_data[twi_index++];
+                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE);
+            }
+            else
+            {
+                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
+            }
+            break;
+        
+        case TW_MR_DATA_ACK:
+            twi_data[twi_index++] = TWDR;
+        case TW_MR_SLA_ACK:
+            if(twi_index < twi_len-1)
+            {
+                TWCR = (1 << TWINT) | (1 << TWEA) | (1 << TWEN) | (1 << TWIE);
+            }
+            else
+            {
+                TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWIE);
+            }
+            break;
+        
+        case TW_MR_DATA_NACK:
+            twi_data[twi_index++] = TWDR;
+            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
+            break;
+        
+        case TW_MT_ARB_LOST:
+            TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN) | (1 << TWIE);
+            break;
+        
+        case TW_MT_SLA_NACK:
+        case TW_MT_DATA_NACK:
+        case TW_MR_SLA_NACK:
+        default:
+            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
+    }
+}