TC77 Shared DataIN & DataOUT on SPI

[jecottrell]

Hello All,

Just wanted a quick sanity check on my understanding...

The TC77 temperature sensor from Microchip uses a shared wire for both data in and data out. I'm assuming there are no problems with other hardware on the bus as long as they are not chip selected?

Thanks,

John

[Humberto]

You are right, as long as you use only one "One Wire device" sharing a
SPI bus, but if you are going to use multiple TC77, - or another "one wire"- you
would use a software SPI and toggle the TRIS register accordingly (SDI or SDO)
to ovoid bus collision.

Humberto

[jecottrell]

Humberto,

Thanks.

My configuration will be:

TC77 (SPI shared DI & DO)
MCP41xxx (SPI pot w/ individual DI & DO)
25LC256 (SPI EEPROM w/ individual DI & DO)

I'm guessing I'll have to setup the SPI comms for each device in code prior to communicating, because, as you have said I'll have to change from 'out' to 'in' for the TC77. But, other than that, there are no problems mixing devices on the same bus? (The chip select keeps the untargeted device from reacting to any data or activity on the bus?

John

[Humberto]

I assume that the PIC is managing the SPI communication, so you have full control
of all the times involved in the comunication handler, hence there would not be any
conflict sharing the SPI bus with a "one wire" device.