I am working on yet another camera/flash trigger. I want it to be very modular and flexible, with every sensor and trigger in its own package, independent of the main controller (So i can forget about the main controller and conect directly a light sensor to the trigger with a 556 in the middle to control de delay, for example)
The conection to de main controller is with 3 wires: +5V, GND and 1 for data, analog or digital. I want the controller to recognize what kind of sensor or trigger is conected in every port. I'm thinking about adding a fourth wire, with a resistor betwen this wire and +5V. From every port, this fourth wire will be conected to an analog multiplexer, controled via I2C (I'm already using I2C for the display and keyboard), and from here, to one of the analog pins of the microcontroller, so I can use the value of the resistor to identify what kind of sensor/trigger is conected to every port.
So now, my questions:
-What will be the reading in the analog input when nothing is conected to the port? Should I put another resistor from the line conecting the multeplexer to the analog pin, to GND to pull it down when nothing is conected? (This will form a voltage divider with the resistor in the sensor when someting is conected, and read 0V when nothing is conected)
-Any sugestion for the multiplexer? The requeriments are: I2C interface, 8 chanels, through hole. Maybe, if there is no big price diference, should I use an I2C A/D converter, with the same requeriments, to save one analog pin in the microcontroller?
-I was thinking about using stereo jacks for the conections betwen the controller and the sensors. Now, with 4 wires, I need a new conector. What type of conector will be advisable for this function?
Thanks in advance, and forgive my bad english.
The conection to de main controller is with 3 wires: +5V, GND and 1 for data, analog or digital. I want the controller to recognize what kind of sensor or trigger is conected in every port. I'm thinking about adding a fourth wire, with a resistor betwen this wire and +5V. From every port, this fourth wire will be conected to an analog multiplexer, controled via I2C (I'm already using I2C for the display and keyboard), and from here, to one of the analog pins of the microcontroller, so I can use the value of the resistor to identify what kind of sensor/trigger is conected to every port.
So now, my questions:
-What will be the reading in the analog input when nothing is conected to the port? Should I put another resistor from the line conecting the multeplexer to the analog pin, to GND to pull it down when nothing is conected? (This will form a voltage divider with the resistor in the sensor when someting is conected, and read 0V when nothing is conected)
-Any sugestion for the multiplexer? The requeriments are: I2C interface, 8 chanels, through hole. Maybe, if there is no big price diference, should I use an I2C A/D converter, with the same requeriments, to save one analog pin in the microcontroller?
-I was thinking about using stereo jacks for the conections betwen the controller and the sensors. Now, with 4 wires, I need a new conector. What type of conector will be advisable for this function?
Thanks in advance, and forgive my bad english.
