Maxim 1-wire serial bus (SL808x)


#1

Hi Guys,

Has anyone tried, or is it even possible, to implement Maxims 1-wire bus on an SL module? Specifically SL808x?
( maximintegrated.com/app-note … .mvp/id/74 )

I haven’t got familiar enough with development yet, so I don’t know how likely it is to be able to achieve the timing spec for it in an OpenAT app…

Alternatively - Maxim give lots of information on implementing 1-Wire via UART (as they are equivalent, besides having a single Rx/Tx line - or like an I2C connection with no clock).

This can be done either by interfacing the Rx and Tx lines ( maximintegrated.com/app-note … mvp/id/214 )

Or by using an interface IC ( maximintegrated.com/datashee … vp/id/2923 )

Since I am intending to use my 8082 module in target mode - will it then be possible to communicate with my 1-wire device using the UART?

Any suggestions welcome!


#2

Hiya,

You will need pretty good control over the GPIO pins if you are going to directly interface the 1-wire bus to your module. I tried it with the Q2686 and there was no way that the module could toggle the GPIO fast enough under OpenAT control. I’m not familiar with the SL808x devices, but you’re probably going to have to implement voltage level shifters as well as the 1 Wire stuff is all 5V.

I ended up using the Maxim I2C 1 wire bridge and some bi-directional level shifters on the I2C lines which worked like a charm. Only issue I had was I had to mess about with the hardware watchdog on the Q26 while doing the bus enumeration routines.

ciao, Dave


#3

Sadly the I2C for the 808x modules is not available yet (much to my dismay) and I cant find any spi based solutions… my only hope is the UART based solution if that is even possible.

The device is a li-ion battery fuel gauge… im not sure how sierra wireless intend developers to achieve such a solution on the 808x modules without I2C even…


#4

Hiya,

Not having I2C available is not much fun. That’s going to put a real crimp in doing any sort of I/O not supported on the module.

My quick hunt didn’t find any SPI gas gauge IC’s either.

Looks like the UART interface is going to be your only option. Sigh…

ciao, Dave


#5

Note that Maxim also provide a UART-to-1-Wire bridge.

Search the forum for previous discussions…