CC2540: cc2540 as 1-wire slave

Philip Man

Part Number: CC2540

I am trying make the cc2540 act as a 1-wire slave device. I can send a presence signal on reset, get a ROM read, but have trouble writing back the ROM information.

I have setup interrupts to HIGH-LOW edge trigger. When I get the edge, I want to hold it low, to send a zero bit.

Problem, is in 6us, the master releases the data line, which is too fast, as I send low to the line, but it takes 12us till it goes low.

Is it possible to do 1-wire communications on cc2540?

over 9 years ago

0 Eirik V over 9 years ago

TI__Guru 56590 points

Hello Philip,
On a 1-wire bus all output signals need to be open-drain. The CC2540 gpio cannot be configured as open-drain, but you could try to configure as input and enable/disable pulldown to simulate an open-drain IO. In the isr routine you can enable the pull-down, but I fear this will not be fast enough for your application.

0 Philip Man over 9 years ago in reply to Eirik V

Intellectual 890 points

I've been using GPIO set to input, and turning it to output when needed (send zero).

Pulldown might not be enough, as pulldown is a weak resistor.

0 Eirik V over 9 years ago in reply to Philip Man

TI__Guru 56590 points

That is true, but did you try it? It might be faster unless the pull-down prove to be to weak for your setup as you suspect.

Bluetooth®︎

Bluetooth forum

CC2540: cc2540 as 1-wire slave