USB to smbus ?

**DeltaFX** · 03-30-2009, 10:16 AM

Hi there,
Building my carputer, I'm looking for a convenient, dedicated (and cheap) way to monitor temperatures and fans in the puter & in the car.

So my first idea was to create a small pcb with Max1668 & MAX 6651 Smbus chips, and connect the things to the mobo' Smbus pin header.... Gnh this stupid board doesn't have any. And I am not ready to solder something to the 91-92 pins of a ram slot (ddr1).

Any ideas ?

**dblack** · 04-02-2009, 09:16 AM

Easy solution would be to find a software/hardware package to interface with your car (all cars 96 and newer have the same OBD2 connector) with this you can monitor more than just temperatures in your car. hit up a search engine with USB OBD2 or USB OBDII.
Second issue is the carputer, its too bad u didnt consider the thermal sensors when you purchased your main board, but there is an easy solution. The overclocking community has designed many systems to monitor temperatures of your computer, my suggestion is to ask around at overclocking forums about thermal monitoring, they will likely send you in the right direction, and you may even be able to use the same system to monitor the temperature of certain areas of your car.

**DeltaFX** · 04-02-2009, 04:29 PM

Thanks.

I already use Speedfan / MBM5 for thermal control of the puter itself ( the frontend reads speedfan's SharedMemory segment, then decides what to do) but there are only 2 temp prob (cpu/ system) and 2 fan headers (cpu / case) without speed control. As speedfan/mbm5 can read smbus easy, my first puter had 2 extra MAX1668 => 10 more temp sensors.

With MAX 6651 & some components, I had extra fan sensors that could change fan speed via speedfan.

And of course, this asrock board doesn't support SMbus via PCI, or they don't want me to now.

Anyway, looks like the way to go is now a 1-Wire network in the car...

PS :OBD-II is already slated.

**Blues** · 04-18-2009, 05:36 PM

The SMBus is a subset of the I²C bus. For the USB or serial port you can buy a complete I²C interface that is also compatible with SMBus devices.

Or you can program your own simple 8-bit microcontroller to read the I²C/SMbus devices and forward the data to the serial or USB port.

http://en.wikipedia.org/wiki/System_Management_Bus
http://en.wikipedia.org/wiki/I²C

SMBus is a subset of I²C that defines stricter electrical and protocol conventions. One purpose of SMBus is to promote robustness and interoperability. Accordingly, modern I²C systems incorporate policies and rules from SMBus, and the line between these two standards is often blurred in practice.

**CanuckMark** · 05-15-2009, 09:15 PM

Did you come up with a solution for this? I am using this very IC (MAX1668) with a PIC microcontroller. The PIC does other things as well, but it's main role is to convert I2C temperature readings from the 1668 to RS232 serial, then sends that data to the computer. It also sends analog data (voltages mainly) and other inputs (ing on, door pins, etc) to the computer.

If you haven't come up with an interface yet, I might be able to strip down my setup a bit and create a firmware file for you - let me know.

Mark