Post by thread:[PIC]: PULSIN & Unknown Number of Sensors

I'm new to PICS & want to create a device with 1 or more sensors (the number of sensors is unknown & variable ie the device could have 1 sensor or 2 or 3 or 4). I want to use the picbasic command PULSIN to measure the pulse width on each sensor. The problem is I don't want to use PULSIN if a sensor does not exist as it takes ~0.5s to time out (is this correct?). So if I test 4 inputs with PULSIN and only 1 sensor exists, the sampling rate will be once every ~1.5s. Any ideas how I get around this? The only way I can think of is to tie a pin high if a sensor is connected on another pin, & then test for that high pin before running PULSIN. This will double the number of inputs required though which I am not keen on. Any other ideas. Many thanks Dominic -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use spam_OUTlistservTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST>

Dominic: As you're going with the Stamp-like approach you could perhaps have the presence of each sensor add a resistive value to a ladder, maybe with the values being an order of magnitude or somesuch apart for differentation, and read the total with the POT command. Then you'd only need one extra pin for multiple sensors (I think this might work for 3 or 4). Bruce Cannon Style Management Systems http://siliconcrucible.com (510) 787-6870 1228 Ceres ST Crockett CA 94525 Remember: electronics is changing your world...for good! {Quote hidden}> or 4). I want to use the picbasic command PULSIN to measure the > pulse width > on each sensor. The problem is I don't want to use PULSIN if a > sensor does > not exist as it takes ~0.5s to time out (is this correct?). So > if I test 4 > inputs with PULSIN and only 1 sensor exists, the sampling rate > will be once > every ~1.5s. Any ideas how I get around this? > > The only way I can think of is to tie a pin high if a sensor is > connected on > another pin, & then test for that high pin before running PULSIN. > This will > double the number of inputs required though which I am not keen > on. Any other > ideas. > > Many thanks > > Dominic > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > use .....listservKILLspam@spam@mitvma.mit.edu?body=SET%20PICList%20DIGEST -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use listservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST>

Dominic, At pic startup you can look for the sensors, for ex: Try to read sensor 1, if you get a timeout then there's no sensor so, you clear a flag to indicate no sensor present (ie: sensor1_present=0) otherwise set a flag (ie: sensor1_present=1) Do this until you tried all possible sensors then, go to the main loop to process all connected sensors using the flag you've set. pseudo-code: if sensor1_present = 1 then read_sensor(sensor1) . . . if sensorn_present... If the sensor is hot-plugable you can re-scan the sensors every minute/hour/day/whatever I don't use picbasic so, I can't help you with real code. Hope this helps Ricardo Seixas {Quote hidden}>I'm new to PICS & want to create a device with 1 or more sensors (the number >of sensors is unknown & variable ie the device could have 1 sensor or 2 or 3 >or 4). I want to use the picbasic command PULSIN to measure the pulse width >on each sensor. The problem is I don't want to use PULSIN if a sensor does >not exist as it takes ~0.5s to time out (is this correct?). So if I test 4 >inputs with PULSIN and only 1 sensor exists, the sampling rate will be once >every ~1.5s. Any ideas how I get around this? > >The only way I can think of is to tie a pin high if a sensor is connected on >another pin, & then test for that high pin before running PULSIN. This will >double the number of inputs required though which I am not keen on. Any other >ideas. > >Many thanks > >Dominic > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >use .....listservKILLspam.....mitvma.mit.edu?body=SET%20PICList%20DIGEST -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST>

How about this idea: Bring your sensor signal into the PIC via a resistor of about 1K, and also connect all your sensor pins, each via a 30K resistor to a single PIC output pin. If the sensor pin tracks the output pin then no sensor is attached. If the sensor pin doesn't track the output pin then a sensor is attached. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) {Original Message removed}