Communication system for current-modulated data transmission via a current loop

A communication system for current-modulated data transmission between a master device and at least one slave device, the communication system comprising:

• a) a current loop;
• b) a master device comprising:
• a first evaluation and control unit;
• a first switching means connected into the current loop and actuable by the first evaluation and control unit, which is configured to open and close the current loop for transmitting data;
• an electrical current source connected to the current loop, which is configured to inject a constant quiescent current into the current loop;
• a first current detection means connected into the current loop and connected to the first evaluation and control unit, the first evaluation and control unit being configured to evaluate the current detected by the first current detection means;
• c) at least one slave device connected to the current loop and comprising:
• a second evaluation and control unit;
• a second switching means connected into the current loop and actuable by the second evaluation and control unit, which is configured to open and close the current loop for transmitting data;
• a third switching means-actuable by the second evaluation and control unit, which is configured to short-circuit the current loop when in its closed state;
• wherein the second evaluation and control unit is configured to temporarily close and then reopen the third switching means during a system configuration detection phase, and wherein the first evaluation and control unit is configured to detect when the at least one slave device is connected to the current loop;
• a second current detection means connected into the current loop and connected to the second evaluation and control unit, the second evaluation and control unit being configured to evaluate the current detected by the second current detection means;
• wherein:
• the first evaluation and control unit is configured to close the first switching means and to inject predetermined system information into the current loop, during a system configuration detection phase;
• and
• the second evaluation and control unit of the at least one slave device is configured to close the second and third switching means and to reopen the third switching means when it received the predetermined system information, during a system configuration detection phase.

A method for automatically detecting the configuration of a communication system for current-modulated data transmission between a master device and at least one slave device, the communication system comprising:

• a) a current loop;
• b) a master device comprising:
• a first evaluation and control unit;
• a first switching means connected into the current loop and actuable by the first evaluation and control unit, which is configured to open and close the current loop for transmitting data;
• an electrical current source connected to the current loop, which is configured to inject a constant quiescent current into the current loop;
• a first current detection means connected into the current loop and connected to the first evaluation and control unit, the first evaluation and control unit being configured to evaluate the current detected by the first current detection means;
• c) at least one slave device connected to the current loop and comprising:
• a second evaluation and control unit;
• a second switching means connected into the current loop and actuable by the second evaluation and control unit, which is configured to open and close the current loop for transmitting data;
• a third switching means-actuable by the second evaluation and control unit, which is configured to short-circuit the current loop when in its closed state;
• wherein the second evaluation and control unit is configured to temporarily close and then reopen the third switching means during a system configuration detection phase, and wherein the first evaluation and control unit is configured to detect when the at least one slave device is connected to the current loop;
• a second current detection means connected into the current loop and connected to the second evaluation and control unit, the second evaluation and control unit being configured to evaluate the current detected by the second current detection means;
• the method comprising the steps of:
• i) closing a first switching means of a master device and closing a second and a third switching means of a first slave device connected to the current loop, whereby the third switching means short-circuits the current loop;
• ii) transmitting, by the master device, a first current-modulated signal via the current loop, which signal is received and evaluated by the first slave device;
• iii) once the first current-modulated signal has been evaluated, opening the third switching means, by the first slave device;
• iv) detecting, in the master device, whether the first slave device is connected to the current loop.