RLY08 I2C Mode

I2C Mode selection
I2C operation is activated when the mode pin is left open circuit.

I2C Operation
I2C Bus
The RLY08 is located on the I2C bus at a factory default address of 0X70. The SCL and SDA lines should have pull-up resistors on them somewhere on the bus. You only require 1 pair of resistors for the whole I2C bus, not specifically for the RLY08. They are normally on the master controller and you may already have them. If not, anything between 1k8 and 10k should work. I recommend 1k8 for best noise immunity.

RLY08 register set
The RLY08 has only two registers, register 0 and acts as a dual purpose register. When written to it is the command register where all of the instructions from the commands section should be sent. When read it returns the software version.
Register 1 is the relay register, when written to it allows the user to change all eight relay positions at once with a single byte. When the register is read it provides the current positions of the relays. If all relays are powered the register would contain 255 (1111 1111), all relays in the un-powered state would result in 0 (0000 0000)

register	Read	Write
0	Software version	Command register
1	Relay states	Relay states

decimal	hex	command
100	0x64	All relays on
101	0x65	Turn relay 1 on
102	0x66	Turn relay 2 on
103	0x67	Turn relay 3 on
104	0x68	Turn relay 4 on
105	0x69	Turn relay 5 on
106	0x6A	Turn relay 6 on
107	0x6B	Turn relay 7 on
108	0x6C	Turn relay 8 on
110	0x6E	All relays off
111	0x6F	Turn relay 1 off
112	0x70	Turn relay 2 off
113	0x71	Turn relay 3 off
114	0x72	Turn relay 4 off
115	0x73	Turn relay 5 off
116	0x74	Turn relay 6 off
117	0x75	Turn relay 7 off
118	0x76	Turn relay 8 off

Changing the RLY08 Address
To change the I2C address of the RLY08 you must have only one module on the bus. Write the 3 sequence commands in the correct order followed by the address. Example; to change the address of a RLY08 currently at 0x70 (the default shipped address) to 0x7A, write the following to address 0x70; (0xA0, 0xAA, 0xA5, 0x7A ). These commands must be sent in the correct sequence to change the I2C address, additionally, No other command may be issued in the middle of the sequence. The sequence must be sent to the command register at location 0, which means 4 separate write transactions on the I2C bus. When done, you should label the module with its address, however if you do forget, just power it up without sending any commands. The RLY08 will flash its address out on the LED. One long flash followed by a number of shorter flashes indicating its address. The flashing is terminated immediately on sending a command to the RLY08 and then becomes a power LED.

Address		Long Flash	Short flashes
Decimal	Hex	Long Flash	Short flashes
112	0x70	1	0
114	0x72	1	1
116	0x74	1	2
118	0x76	1	3
120	0x78	1	4
122	0x7A	1	5
124	0x7C	1	6
126	0x7E	1	7

Take care not to set more than one module to the same address, there will be a bus collision and very unpredictable results.