The invention relates to a laboratory sample distribution system and to a method of operating a laboratory sample distribution system. WO 2013/064656 A1 discloses a laboratory sample distribution system comprising a number of sample container carriers. The system further comprises a number of transport modules, wherein each transport module comprises a transport surface. The transport surfaces of the transport modules arranged adjacent to one another form a transport plane. The system further comprises controllable drive means being arranged below the transport surface of a respective transport module and being adapted to move sample container carriers on the transport surface. The system comprises a control unit for controlling the drive means.

US 2015/0316974 A1 discloses a slave controller including an impedance element and a processor configured to generate an identifier of the slave controller based on an electrical value of electric energy entering the impedance element. US 2010/0185841 A1 discloses the determining of addresses of electrical components arranged in a daisy chain.

US 2010/0185784 A1 discloses an automatic address assignment for a communication bus.

It is the object of the invention to provide for a laboratory sample distribution system and a method of operating a laboratory sample distribution system being highly scalable and modular. The invention solves this object by means of a laboratory sample distribution system according to claim 1 and by means of a method of operating a laboratory sample distribution system according to claim 5.

The laboratory sample distribution system comprises a number (e.g. 2 to 2000) of sample container carriers being adapted to carry a sample container, typically a sample tube comprising a medical sample.

The laboratory sample distribution system further comprises a central controller having a network interface. The central controller may e.g. be incorporated in form of a personal computer. The network interface is adapted to be coupled to a network and e.g. comprises two network terminals, wherein two electric bus wires can be connected to the network terminals.

The laboratory sample distribution system further comprises a number (e.g. 2 to 500) of transport modules. Each transport module comprises a planar transport surface. The transport surfaces of the transport modules being arranged adjacent to one another form a transport plane for the sample container carriers.

Each transport module further comprises controllable drive means. The drive means are arranged below the transport surface of a respective transport module. The drive means are adapted to move sample container carriers on the transport surface, e.g. be generating a magnetic field being time and position dependent. The magnetic field may interact with a magnetically active element, e.g. a permanent magnet, being part of the sample container carrier.

Each transport module further comprises a control unit for controlling the drive means. The control unit may e.g. be embodied as a microcontroller. The control unit comprises a network inter- face, e.g. including network terminals of the microcontroller.

The central controller and the control units of the transport modules are connected with one another by means of their corresponding network interfaces. The network interfaces may e.g. be electrically coupled be means of electrical wires to enable a data communication between the central controller and the control units. The central controller and the control units may be connected with one another by means of a field bus. Reference is further made to the relevant technical literature regarding field buses.

Each control unit comprises a first addressing terminal and a second addressing terminal, e.g. being embodied as ports of the microcontroller.

The first addressing terminals and the second addressing terminals of the respective control units are configurable as input terminals or output terminals. The first addressing terminals and the second addressing terminals of the respective control units may e.g. be embodied as so called General-purpose input/output (GPIO), i.e. a generic pin on an integrated circuit whose behavior, including whether it is an input or output pin, is controllable at run time. If configured as an output, the addressing terminals may operate as open collector or open drain terminals. The addressing terminals of the control units are connected with one another sequentially in a daisy chain topology. The daisy chain topology is a wiring scheme in which multiple devices are wired together in sequence (or in a ring, not embodied according to the invention). According to the invention, the first addressing terminal of the control unit being the first control unit in the daisy chain sequence is connected to a first reference potential, e.g. ground GND. The second addressing terminal of the control unit being the first control unit in the daisy chain sequence is connected to the first terminal of the control unit being the second control unit in the daisy chain sequence. The second addressing terminal of the control unit being the second control unit in the daisy chain sequence is connected to the first terminal of the control unit being the third con- trol unit in the daisy chain sequence, and so forth. Finally, the second addressing terminal of the control unit being the last control unit in the sequence is connected to a second reference potential.

The first reference potential and the second reference potential may be identical, e.g. ground potential. The network interface of the central controller and the network interfaces of the control units may be embodied as RS485 network interfaces. Reference is further made to the relevant technical literature regarding the RS485 standard.

The method of operating the laboratory sample distribution system comprises the following steps. First, the first addressing terminals and the second addressing terminals of the respective control units are respectively configured as input terminals.

Then, the states of the first addressing terminals and of the second addressing terminals of the respective control units are read.

A first address is assigned to the control unit, which has a predetermined initializing state (logi- cal state) at its first addressing terminal, e.g. the logical state 0.

In case of an error free operation, the first addressing terminal of the control unit being the first control unit in the sequence is connected to the first reference potential, wherein the first reference potential corresponds to the predetermined initializing state. The respective first addressing terminals of the remaining control units see a potential which differs from the first reference potential. For that purpose, pull-up-resistors or pull-down-resistors may be provided at each connection between the respective first and second addressing terminals within the daisy-chain topology, ensuring that a defined potential is present, if the first and second addressing terminals are configured as inputs. Concluding, only the first control unit in the sequence reads the predetermined initializing state at its first addressing terminal, wherein the remaining control units read another or opposite state at their corresponding first addressing terminals. Therefore, this behavior can be used to assign the first address to the first control unit in the daisy chain.

Then, the second addressing terminal of the control unit having the first address is configured as an output terminal and a predetermined potential is output at the second addressing terminal of the control unit having the first address. The predetermined potential output at the second addressing terminal may be the same as the first reference potential, e.g. GND. Typically, the potential at the second addressing terminal is held constant by means of a pull-up or a pulldown resistor, when the second addressing terminal is configured as an input. When the second addressing terminal is configured as an output and the predetermined potential is output at the second addressing terminal, the potential changes to the predetermined potential. If e.g. a pull-up resistor is used, the potential changes from a supply voltage to GND.

This causes that the second control unit in the daisy chain detects a change of the state at its first addressing terminal and successively a second address is assigned to the second control unit.

These steps are repeated for the control units in the sequence following the control unit having the second address until the last control unit in the chain is reached.

The last control unit can be determined based on the fact that the potential at its second addressing terminal is the second reference potential at the beginning of the addressing sequence.

Self-evidently, the above steps can be reversed, thus assigning the first address to the control unit having the second reference potential at its second addressing terminal at the beginning of the addressing sequence.

The invention will now be described in detail with respect to the drawings. In the drawings,

Fig. 1 schematically shows a laboratory sample distribution system according to the invention having a number of transport modules, and Fig. 2 schematically shows a wiring scheme connecting a central controller and a plurality of control units of the laboratory sample distribution system shown in figure 1 .

Fig. 1 schematically shows a laboratory sample distribution system 100. The laboratory sample distribution system 100 comprises a number of sample container carriers 140 being movably arranged on a transport plane 1 10. The transport plane 1 10 is formed of 4 transport surfaces 121 being arranged adjacent to one another, wherein the transport surfaces 121 are part of 4 transport modules 120.

Each transport module 120 further comprises controllable drive means 122 in form of electromagnets being arranged in rows and columns under the transport surface 121 and being adapted to move sample container carriers 140 on the transport surface 121 . For the purpose of explanation, only a single drive means 122 is depicted.

The sample container carriers 140 comprise a permanent magnet (not shown) interacting with a magnetic field generated by means of the electro-magnets 122, such that a desired magnetic driving force is applied to the sample container carriers 140. Regarding the drive means 122 and the basic mechanical arrangement of the transport modules, reference is also made to the disclosure of WO 2013/064656 A1 .

Each transport module 120 comprises a control unit 123 for controlling the drive means 122.

Now referring to Fig. 2, the laboratory sample distribution system 100 comprises a central controller 150 in form of a personal computer having a RS485 network interface 151 . The control units 123_1 to 123_n respectively comprise a RS485 network interface 124 having two connectors, wherein the central controller 150 and the control units 123_1 to 123_n of the transport modules 120 are connected with one another by means of their corresponding network interfaces 151 , 124, respectively. For that purpose, the network interfaces 151 , 124 are conventionally electrically connected by means of two electrical bus wires 127. Each control unit 123_1 to 123_n comprises a first addressing terminal 125 and a second addressing terminal 126, wherein the addressing terminals 125, 126 of the control units 123_1 to 123_n are electrically connected with one another sequentially in a daisy chain topology, as depicted. The first addressing terminal 125 of the control unit 123_1 being the first in the sequence is connected to a reference potential, namely GND. The second addressing terminal 126 of the control unit 123_n being the last in the sequence is also connected to the reference potential GND, e.g. by means of a terminator element. The respective first addressing terminals 125 and the respective second addressing terminals 126 of the control units 123_1 to 123_n can be configured as input terminals or output terminals.

Each electrical connection between a respective first addressing terminal 125 and second addressing terminal 126 is electrically pulled up to a supply voltage VDD by means of correspond- ing pull-up resistors 128 comprised in each control unit 123_1 to 123_n. The addressing terminals 125 and 126 may be configured as open drain or open collector outputs, such that the terminals may pull the potential at the output to GND or may have a high impedance state, such that the potential is pulled up to VDD.

The electrical wiring between the control units 123_1 to 123_n may e.g. be embodied by means of connection cables having a connector at each end, e.g. an 8P8C connector. The control units may be connected to their neighbors by means of two connection cables, one connection cable to the left neighbor and one connection cable to the right neighbor. The connection cable used to connect the control unit 123_1 to the central controller 150 may differ from the remaining connection cables and may electrically connect the first addressing terminal 125 to GND. The network addresses of the control units 123_1 to 123_n used to communicate by means of the network interface, i.e. the RS485 network, are assigned as follows.

At the beginning, e.g. after a reboot of the laboratory sample distribution system 100, the respective first addressing terminals 125 and the respective second addressing terminals 126 of the control units 123 are configured as input terminals. The control units 123_1 to 123_n respectively read the states of their first addressing terminals 125 and of the second addressing terminals 126.

The first addressing terminal 125 of the control unit 123_1 reads a state corresponding to GND, i.e. a predetermined initializing state. The first addressing terminals 125 of the remaining control units 123_2 to 123_n read a different state corresponding to VDD, i.e. not the predetermined initializing state. Therefore, a first address is assigned to the control unit 123_1 .

Subsequently, the control unit 123_1 configures its second addressing terminal 126 as an output terminal and pulls the output to GND.

As a consequence, the control unit 123_2 detects a change of the state at its first addressing terminal 126, such that a second address can be assigned to the control unit 123_2.

Subsequently, the control unit 123_2 configures its second addressing terminal 126 as an output terminal and pulls the output to GND.

As a consequence, the control unit following control unit 123_2 detects a change of the state at its first addressing terminal 125, such that a third address can be assigned to this control unit. These steps are repeated until an address n is assigned to the last control unit 123_n.

The last control unit 123_n is identified by the fact that its second addressing terminal 126 constantly reads the predetermined initializing state.

Self-evidently, it is possible to reverse the address assignment scheme from "left to right" to "right to left", such the first address is assigned to the last control unit 123_n and so on. In case of an error, the addresses may e.g. be assigned beginning from one side until no further address can be assigned in the given direction, e.g. because a control module is defect, the wiring is defect, etc. If such an error is detected, the further addresses may successively be assigned from the other direction.

After the addresses have been assigned to the control units 123_1 to 123_n, the central control- ler 150 may e.g. transmit commands to the control units 123_1 to 123_n.