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.
You need a pin with an external interrupt to read data and any other pin to send data. Transistor method is recommended.
You will need one free 8-bit timer with output compare match interrupt.
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_Tvalue as64us, it must match timer initialization code,(F_CPU / CLUNET_TIMER_PRESCALER) / 15625must 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 compareregister; - CLUNET_ENABLE_TIMER_COMP and CLUNET_DISABLE_TIMER_COMP - code to enable/disable timer
output compare matchinterrupt; - CLUNET_ENABLE_TIMER_OVF and CLUNET_DISABLE_TIMER_OVF - code to enable/disable timer
overflowinterrupt; - CLUNET_INIT_INT - code to init external interrupt (read pin);
- CLUNET_TIMER_COMP_VECTOR - timer
output compare matchinterrupt vector; - CLUNET_TIMER_OVF_VECTOR - timer
overflowinterrupt vector`; - CLUNET_INT_VECTOR -
external interruptvector.
Default configuration file is optimised for ATMEGA8 / 8MHz.
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_ADDRESSfor multicast - prio - packet priority:
CLUNET_PRIORITY_NOTICE,CLUNET_PRIORITY_INFO,CLUNET_PRIORITY_MESSAGE,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));
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.
- ATMEGA8;
- ATMEGA16;
- ATMEGA64.
- 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.
Alexey 'Cluster' Avdyukhin