HV Analogue Input Expander

[FrankMcAlinden]

Hi Ed


This is one of the posts dated 12/3/06 from the Homevision list

HTH
Frank
PS.....I think they are getting preety close....

************************************************** ***********

Paul (another board member) and I set out to build an I2C to 1-wire
interface for HV using a Dallas/Maxim DS2482-800.

The DS2482 is an I2C to 1-wire bridge device, providing 8 discrete
1-wire bus connections through a single I2C interface.

We have succesfully connected this chip to HV's I2C bus, and can read
the various registers.

We are having trouble writing to the device because all of the write
commands involve 2 steps. First, you write an address to a pointer
register, and then you write you 8-bit payload to the bus, and the
device should store it at the register you defined.

The datasheet explicitly shows these multi-byte commands as continuous
I2C communications using the Repeated Start Command. I2C at it's most
basic level involves declaring a START, followed by a write or read to
an address, followed by a STOP. The repeated start allows multiple
commands to be strung back to back without a stop, thereby holding
control of the bus.

It is our understanding at this point, that HV only provides a
mechanism for writing or reading single bytes, and these commands are
issued as a START, Write/Read, STOP. Therefore, the 2-command
sequences that the DS2482 expects to see as START, Write1, ReSTART,
Write2, Stop come through as START, Write1, STOP... START, Write2,
STOP. We believe this is confusing the DS2482 state machine and
payload bytes are being interpretted as commands...

Is there any way to generate the more complex I2C commands in HV using
CSI's HV software or Schelte's software?

Thanks in advance!!
-Russ (and Paul)