From 60797c8439f472c68f374acc11337e362a8836eb Mon Sep 17 00:00:00 2001
From: yiancar <yiangosyiangou@cytanet.com.cy>
Date: Thu, 12 Jul 2018 11:50:55 +0300
Subject: [PATCH] Add I2C slave library
- Add I2C slave library for general use.
---
drivers/avr/i2c_slave.c | 100 ++++++++++++++++++++++++++++++++++++++++
drivers/avr/i2c_slave.h | 19 ++++++++
2 files changed, 119 insertions(+)
create mode 100755 drivers/avr/i2c_slave.c
create mode 100755 drivers/avr/i2c_slave.h
diff --git a/drivers/avr/i2c_slave.c b/drivers/avr/i2c_slave.c
new file mode 100755
index 0000000000..3edf85b12b
--- /dev/null
+++ b/drivers/avr/i2c_slave.c
@@ -0,0 +1,100 @@
+/* Library made by: g4lvanix
+ * Github repository: https://github.com/g4lvanix/I2C-slave-lib
+ */
+
+#include <avr/io.h>
+#include <util/twi.h>
+#include <avr/interrupt.h>
+
+#include "i2c_slave.h"
+
+void i2c_init(uint8_t address){
+ // load address into TWI address register
+ TWAR = (address << 1);
+ // 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_stop(void){
+ // clear acknowledge and enable bits
+ TWCR &= ~( (1<<TWEA) | (1<<TWEN) );
+}
+
+ISR(TWI_vect){
+
+ // temporary stores the received data
+ uint8_t data;
+
+ // own address has been acknowledged
+ if( (TWSR & 0xF8) == TW_SR_SLA_ACK ){
+ buffer_address = 0xFF;
+ // clear TWI interrupt flag, prepare to receive next byte and acknowledge
+ TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
+ }
+ else if( (TWSR & 0xF8) == TW_SR_DATA_ACK ){ // data has been received in slave receiver mode
+
+ // save the received byte inside data
+ data = TWDR;
+
+ // check wether an address has already been transmitted or not
+ if(buffer_address == 0xFF){
+
+ buffer_address = data;
+
+ // clear TWI interrupt flag, prepare to receive next byte and acknowledge
+ TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
+ }
+ else{ // if a databyte has already been received
+
+ // store the data at the current address
+ rxbuffer[buffer_address] = data;
+
+ // increment the buffer address
+ buffer_address++;
+
+ // if there is still enough space inside the buffer
+ if(buffer_address < 0xFF){
+ // clear TWI interrupt flag, prepare to receive next byte and acknowledge
+ TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
+ }
+ else{
+ // Don't acknowledge
+ TWCR &= ~(1<<TWEA);
+ // clear TWI interrupt flag, prepare to receive last byte.
+ TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEN);
+ }
+ }
+ }
+ else if( (TWSR & 0xF8) == TW_ST_DATA_ACK ){ // device has been addressed to be a transmitter
+
+ // copy data from TWDR to the temporary memory
+ data = TWDR;
+
+ // if no buffer read address has been sent yet
+ if( buffer_address == 0xFF ){
+ buffer_address = data;
+ }
+
+ // copy the specified buffer address into the TWDR register for transmission
+ TWDR = txbuffer[buffer_address];
+ // increment buffer read address
+ buffer_address++;
+
+ // if there is another buffer address that can be sent
+ if(buffer_address < 0xFF){
+ // clear TWI interrupt flag, prepare to send next byte and receive acknowledge
+ TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
+ }
+ else{
+ // Don't acknowledge
+ TWCR &= ~(1<<TWEA);
+ // clear TWI interrupt flag, prepare to receive last byte.
+ TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEN);
+ }
+
+ }
+ else{
+ // if none of the above apply prepare TWI to be addressed again
+ TWCR |= (1<<TWIE) | (1<<TWEA) | (1<<TWEN);
+ }
+}
diff --git a/drivers/avr/i2c_slave.h b/drivers/avr/i2c_slave.h
new file mode 100755
index 0000000000..3fda7f8c09
--- /dev/null
+++ b/drivers/avr/i2c_slave.h
@@ -0,0 +1,19 @@
+/* Library made by: g4lvanix
+ * Github repository: https://github.com/g4lvanix/I2C-slave-lib
+
+ Info: Inititate the library by giving the required address.
+ Read or write to the necessary buffer according to the opperation.
+ */
+
+#ifndef I2C_SLAVE_H
+#define I2C_SLAVE_H
+
+volatile uint8_t buffer_address;
+volatile uint8_t txbuffer[0xFF];
+volatile uint8_t rxbuffer[0xFF];
+
+void i2c_init(uint8_t address);
+void i2c_stop(void);
+ISR(TWI_vect);
+
+#endif // I2C_SLAVE_H