CLUNET

The CLUNET library - is a simple single-wire peer-to-peer network driver for AVR microcontrollers, perfect way to interconnect microcontrollers in your house.

Features:

• Requires only a few cheap additional components;
• Using only a single wire;
• Using only two pins;
• There is no master device, all devices are equal;
• You can use a very long cable, more than 100 meters;
• You don't need to care about collisions;
• Automatic CRC calculation and CRC check;
• Pseudo multitasking using interrupts;
• Up to 255 devices on one bus.

How to use

Hardware part

You need a pin with an external interrupt to read data and any other pin to send data. Transistor method is recommended.

Software part

You will need one free 8-bit timer with output compare match interrupt.

Configuration####

Edit clunet_config.h and change some values:

• CLUNET_DEVICE_ID - address of the device (0-254);
• CLUNET_DEVICE_NAME - name of the device (optional);
• CLUNET_SEND_BUFFER_SIZE - send buffer size and maximum output packet size (memory usage);
• CLUNET_READ_BUFFER_SIZE - read buffer size and maximum input packet size (memory usage);
• CLUNET_WRITE_PORT and CLUNET_WRITE_PIN - port and pin to send data;
• CLUNET_READ_PORT and CLUNET_READ_PIN - port and pin to read data, should be connected directly to the line;
• CLUNET_WRITE_TRANSISTOR - define if you are using a transistor on output pin (see schematics);
• CLUNET_TIMER_PRESCALER - prescaler for timer, define it to autocalculate CLUNET_T value as 64us, it must match timer initialization code, (F_CPU / CLUNET_TIMER_PRESCALER) / 15625 must be >= 8 and <= 24, thus 64 is the optimal value for 8MHz;
• CLUNET_T - T value, it's a time period between signals in timer ticks, length of logical 0 is T, and logical 1 is 3*T, lower T is faster while higher T is more stable, it's autocalculated as 64us based on CLUNET_TIMER_PRESCALER if not defined;
• CLUNET_TIMER_INIT - code to init timer (normal mode);
• CLUNET_TIMER_REG - timer/counter register;
• CLUNET_TIMER_REG_OCR - timer/counter output compare register;
• CLUNET_ENABLE_TIMER_COMP and CLUNET_DISABLE_TIMER_COMP - code to enable/disable timer output compare match interrupt;
• CLUNET_ENABLE_TIMER_OVF and CLUNET_DISABLE_TIMER_OVF - code to enable/disable timer overflow interrupt;
• CLUNET_INIT_INT - code to init external interrupt (read pin);
• CLUNET_TIMER_COMP_VECTOR - timer output compare match interrupt vector;
• CLUNET_TIMER_OVF_VECTOR - timer overflow interrupt vector`;
• CLUNET_INT_VECTOR - external interrupt vector.

Default configuration file is optimised for ATMEGA8 / 8MHz.

Code

Include "clunet.h" and create callback function to receive data:

#include "clunet.h"

void data_received(unsigned char src_address, unsigned char dst_address, unsigned char command, char* data, unsigned char size)
{
	/* your code here */
}

Add initialization code and enable interrupts:

int main (void)
{
	clunet_init();
	clunet_set_on_data_received(data_received);	
	sei();

Also you can use clunet_set_on_data_received_sniff() to set callback function which will receive all packets, not only for this device.

Function to send data:

void clunet_send(unsigned char address, unsigned char prio, unsigned char command, char* data, unsigned char size);

• address - address of destination device or CLUNET_BROADCAST_ADDRESS for multicast
• prio - packet priority:
  1. CLUNET_PRIORITY_NOTICE,
  2. CLUNET_PRIORITY_INFO,
  3. CLUNET_PRIORITY_MESSAGE,
  4. CLUNET_PRIORITY_COMMAND;
• command - command ID (0-255), note that some IDs are occupied by predefined commands (see clunet.h) and some are reserved (see below);
• data - pointer to data if any;
• size - data size.

Sample code:

char buffer[1];
buffer[0] = 1;
clunet_send(CLUNET_BROADCAST_ADDRESS, CLUNET_PRIORITY_MESSAGE, CLUNET_COMMAND_DEVICE_POWER_INFO, buffer, sizeof(buffer));

while (clunet_ready_to_send()); // wait while sending, otherwise next call will replace output buffer
                                // clunet_ready_to_send() returns current task priority
                                // or 0 if output buffer is not busy

char *hello = "Hello world!";
clunet_send(1, CLUNET_PRIORITY_INFO, 100, hello, strlen(hello));

Reserved commands

There are some reserved commands:

• CLUNET_COMMAND_DISCOVERY (0x00) - send this command as broadcast packet to find all devices in your network, devices will answer with command CLUNET_COMMAND_DISCOVERY_RESPONSE (0x01) and CLUNET_DEVICE_NAME in data section;
• CLUNET_COMMAND_REBOOT (0x02) - send this command to reboot a device;
• CLUNET_COMMAND_BOOT_CONTROL - (0x03) reserved for bootloader and firmware update;
• CLUNET_COMMAND_BOOT_COMPLETED (0x04) - sent by device on start (call of clunet_init()), data is value of MCUCSR register, so your can determine reset source;
• CLUNET_COMMAND_PING (0xFE) - ping, you can test line using this command, device(s) will answer with CLUNET_COMMAND_PING_REPLY (0xFF) and same data.

Tested on

• ATMEGA8;
• ATMEGA16;
• ATMEGA64.

Known bugs/problems

• Any data on bus will slow down every connected device a little.
• No delivery check, you can make it in your application code if necessary.

Author/contacts

Alexey 'Cluster' Avdyukhin

clusterrr@clusterrr.com

https://github.com/ClusterM

http://clusterrr.com