Hi,

Hope you might be able to suggest a solution to the following problem.
A) AT89S8252 based experiment board with eight 1-wire temperature sensors connected to P3.0 which also has a MAX232 connected to it. 4.7K pull up resistor on 1-wire bus. This works, all 1-wire sensors detected and return readings. 1-wier is powered, not parasitic.
B) Decide to use serial port so PC can read temperatures from devices. So get serial port working.
C) Add back in the 1-wire stuff, but use P1.0 pin (nothing connected to it) for 1-wire rather than the P3.0 pin now used for serial. This doesn't work quite right. The sensors are detected and read, but the power-on-reset value is always returned, I know it's the POR value as there is a mixture of 1-wire sensor types and they have different POR values.
D) Add a delay between RXing the read sensor command and performing the actual read sensor code (and 1-wire to use P3.0), to allow the 1-wire devices to be connected to P3.0. Issue serial port command to read sensors, connect the 1-wire devices and they are detected and sensible temperature values returned !
E) Go back to code without serial port and use P1.0 - P1.7, all devices detected but only POR value returned.

I've tried disabling interrupts while reading the sensors and that made no difference when using P1.0, still detect but only read POR.

Has anyone got any explanation and/or suggestions for me to try to get the 1-wire working on any P1 pin ?

Thanks in advance,

Luke