1 files changed, 111 insertions, 0 deletions
diff --git a/platforms/avr/drivers/i2c_slave.c b/platforms/avr/drivers/i2c_slave.c
new file mode 100644
index 0000000000..2907f164c0
--- /dev/null
+++ b/platforms/avr/drivers/i2c_slave.c
@@ -0,0 +1,111 @@
+/*  Copyright (C) 2019 Elia Ritterbusch
+ +
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+/* Library made by: g4lvanix
+ * GitHub repository: https://github.com/g4lvanix/I2C-slave-lib
+ */
+
+#include <stddef.h>
+#include <avr/io.h>
+#include <util/twi.h>
+#include <avr/interrupt.h>
+#include <stdbool.h>
+
+#include "i2c_slave.h"
+
+#if defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+#    include "transactions.h"
+
+static volatile bool is_callback_executor = false;
+#endif  // defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+
+volatile uint8_t i2c_slave_reg[I2C_SLAVE_REG_COUNT];
+
+static volatile uint8_t buffer_address;
+static volatile bool    slave_has_register_set = false;
+
+void i2c_slave_init(uint8_t address) {
+    // load address into TWI address register
+    TWAR = address;
+    // set the TWCR to enable address matching and enable TWI, clear TWINT, enable TWI interrupt
+    TWCR = (1 << TWIE) | (1 << TWEA) | (1 << TWINT) | (1 << TWEN);
+}
+
+void i2c_slave_stop(void) {
+    // clear acknowledge and enable bits
+    TWCR &= ~((1 << TWEA) | (1 << TWEN));
+}
+
+ISR(TWI_vect) {
+    uint8_t ack = 1;
+
+    switch (TW_STATUS) {
+        case TW_SR_SLA_ACK:
+            // The device is now a slave receiver
+            slave_has_register_set = false;
+#if defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+            is_callback_executor = false;
+#endif  // defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+            break;
+
+        case TW_SR_DATA_ACK:
+            // This device is a slave receiver and has received data
+            // First byte is the location then the bytes will be writen in buffer with auto-increment
+            if (!slave_has_register_set) {
+                buffer_address = TWDR;
+
+                if (buffer_address >= I2C_SLAVE_REG_COUNT) {  // address out of bounds dont ack
+                    ack            = 0;
+                    buffer_address = 0;
+                }
+                slave_has_register_set = true;  // address has been received now fill in buffer
+
+#if defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+                // Work out if we're attempting to execute a callback
+                is_callback_executor = buffer_address == split_transaction_table[I2C_EXECUTE_CALLBACK].initiator2target_offset;
+#endif  // defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+            } else {
+                i2c_slave_reg[buffer_address] = TWDR;
+                buffer_address++;
+
+#if defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+                // If we're intending to execute a transaction callback, do so, as we've just received the transaction ID
+                if (is_callback_executor) {
+                    split_transaction_desc_t *trans = &split_transaction_table[split_shmem->transaction_id];
+                    if (trans->slave_callback) {
+                        trans->slave_callback(trans->initiator2target_buffer_size, split_trans_initiator2target_buffer(trans), trans->target2initiator_buffer_size, split_trans_target2initiator_buffer(trans));
+                    }
+                }
+#endif  // defined(USE_I2C) && defined(SPLIT_COMMON_TRANSACTIONS)
+            }
+            break;
+
+        case TW_ST_SLA_ACK:
+        case TW_ST_DATA_ACK:
+            // This device is a slave transmitter and master has requested data
+            TWDR = i2c_slave_reg[buffer_address];
+            buffer_address++;
+            break;
+
+        case TW_BUS_ERROR:
+            // We got an error, reset i2c
+            TWCR = 0;
+        default:
+            break;
+    }
+
+    // Reset i2c state machine to be ready for next interrupt
+    TWCR |= (1 << TWIE) | (1 << TWINT) | (ack << TWEA) | (1 << TWEN);
+}