i2c and PC motherboard

springer

New Member
Anyone done any work with interfacing a picaxe to the i2c chip on a pc motherboard?
(also... a search for i2c produced 0 results...odd!)
 

Tom2000

Senior Member
I don't think PC motherboards are equipped with i2c ports. You'd have to bit bang something through the parallel port... not an easy task with modern operating systems.

Good luck!

Tom
 

hippy

Technical Support
Staff member
I'm not sure what this "i2C chip on a PC's motherboard" is; more info would help.

I2C won't turn up in the searches because words of three letter or less are discarded when searching :-(
 

springer

New Member
mine does.
its an old asus nrl-ls server. it's loaded with linux and lots of drives, and sits 'quietly' in the corner as a ftp/print/smb/http/router etc
then the other day, with nothing else to do, i re-read the manual (sad!) and came across this....
SMBus connector (6-1 pin J5)
This connector allows you to connect SMBus (System Management
Bus) devices. Devices communicate with an SMBus host and/or other
SMBus devices using the SMBus interface. SMBus is a specific
implementation of an I2C bus, a multi-device bus that allows multiple
chips to connect to the same bus and enable each one to act as a
master by initiating data transfer.

pin1 floating
pin2 smbclock
pin3 nc
pin4 gnd
pin5 smbdata
pin6 +3.3v
 
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Brietech

Senior Member
Most motherboards (in fact, i think most devices!) use i2c for SOMETHING. It is most likely the fan controllers and temperature sensors on the motherboard. I doubt there is a whole lot of fun you can have with it (unless you get a kick out of speeding up fans or some such).
 

hippy

Technical Support
Staff member
SMBus is similar to, but not quite, I2C. Although I don't know the specific differences I recall that the two are not compatible. SMBus is often used for ACPI ( power saving etc ), Smart Battery monitoring and I believe there's an SMBus connection between PC and Monitor to allow modern Monitors to identify themselves and their capabilities.

I assume the PC acts as a host so I'm not sure how that would cope with a PICAXE acting as a parallel host. As a client SMBus device, I expect that will be as problematic as getting a PICAXE to act as an I2C Slave.
 

andrew_qld

Senior Member
Depends on what you want to do.

I have seen a lot of i2c temperature & fan speed sensors on PC mother boards and often thought that you should be able to do something with them. You would have to be careful that the BIOS didn't think the motherboard was overheating or something and shut the PC down. Most mobile phones have an i2c or SPI bus for stuff like LED, LCD and keypad control too.

I have seen i2c and SPI adaptors that talk through parallel ports if you wanted to get a sensor to talk to a PC. These are mainly for programming AVR and PIC processors and programming i2c eeproms.
 
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