VIA EPIA-M I2C on-board connector - found interesting article on viaarena.com forums

mpattonm · 01-25-2005, 08:03 AM

for those that find this article as interesting as I did:

The VIA EPIA ME6000 has a I2C Connector on the motherboard. This is, what the User Manual says about:

PIN/Signal
1/+3.3V
2/+3.3V
3/EL-ON (?????)
4/SMBCK
5/SMBDT
6/GND

My trial was to connect a Dallas/Maxim DS1621 temperature sensor. The pins of the DS1621 are as follows:
1/SDA - 2-Wire Serial Data Input/Output
2/SCL - 2-Wire Serial Clock
3/Tout - Thermostat Output Signal
4/GND - Ground
5/A2 - Chip Address Input
6/A1 - Chip Address Input
7/A0 - Chip Address Input
8/Vdd - Power Supply Voltage

Now connect

I2C Connector - DS1621
1/+3.3V - 8/Vdd
4/SMBCK - 2/SCL
5/SMBDT - 1/SDA
6/GND - 4/GND
6/GND - 5/A2, 6/A1, 7/A0

NOTE: Address Pins A0-A2 give zero-bits if connected to GND, and one-bits if connected to Vdd. This feature is for specifying an address of the sensor if more than one is connected to the bus.

Next install lm-sensors, on my Debian Sarge 2.6.8-1-386 I did it with
# apt-get install lm-sensors
# sensors -v
sensors version 2.8.7 with libsensors version 2.8.7

Now the relevant modules need to inserted (via insmod or modprob), here is the relevant part of
# lsmod
Module Size Used by
ds1621 8452 0
i2c_isa 2304 0
vt1211 15876 0
i2c_sensor 2944 2 ds1621,vt1211
i2c_viapro 6924 0
i2c_dev 9984 0
i2c_core 22416 6 ds1621,i2c_isa,vt1211,i2c_sensor,i2c_viapro,i2c_de v

sensors-detect did not detect the DS1621, but it works now:
# sensors
ds1621-i2c-0-48
Adapter: SMBus Via Pro adapter at 0500
temp: +26.00°C (low = +15.0°C, high = +10.0°C) ALARM (LOW,HIGH)

Helmut Wollmersdorfer

rando · 01-25-2005, 09:05 AM

Yah, you can use it but as far as I can tell, it's an SMBUS port and not a full I2C port. There are a few posts here from a few months back where we discussed this port for use in Seth's radio project. So far nobody has been able to produce any chip docs that show it does anything more than SMBUS. The lm-sensors Linux drivers are no exception as they can only send SMBUS messages.

If you've got a device that can operate using only the limited SMBUS protocol, it's great. If you need I2C, you still have to look elsewhere. For instance, I wrote a small Windows library for bit banging I2C that works over the parallel or serial port.