Can transceiver monitor
A CAN Transceiver monitor configured to perform operational tests without polluting the data transfer bus with test messages, while maintaining the CAN controller without any error flag triggered and with the message sent validated. Since the monitor handles the testing and cuts the connection to the network, none of the test messages can reach the network and therefore cause unnecessary bus load.
1 . A Controller Area Network (CAN) Transceiver monitor comprising:
two CAN inputs including CAN H input and CAN L input;
two CAN outputs including CAN H output and CAN L output;
a CAN type selector;
a test enable port;
at least a test circuit, an ACK detection circuit and an ACK response circuit;
the CAN Transceiver monitor is configured to install in series in a CAN bus line comprising a CAN H line and a CAN L line, after a CAN transceiver;
wherein
the test enable port is configured to enable the monitor to perform in-line and real time testing of the two CAN inputs while ensuring continuous and uninterrupted data flow of the two CAN inputs to the two CAN outputs,
the CAN H input, the CAN L input, the CAN H output and the CAN L output are part of a CAN bus line and are required to decipher transmitted CAN data frames as well as to ensure transmission of said data frames to the CAN bus line in case of no test operation,
the test enable port is configured to highjack the data frames for testing purposes or, by default, to propagate the data frames present on the two CAN input signals to the CAN bus line, wherein a test circuit comprises electronic and additional logic circuits configured to commute between a testing mode and a default operation mode,
a ACK detection circuit comprises logic circuits configured to determine a position of an ACK bit within a CAN data frame, and
the ACK response circuit is configured to output an ACK bit of a CAN data frame in the CAN bus line for a set duration of time.
2 . The CAN Transceiver monitor according to claim 1 , wherein the CAN type selector is configured to discern and commute the analysis of the CAN Transceiver monitor between two CAN protocol types including CAN classic and CAN-FD.
3 . The CAN monitor according to claim 1 , wherein the real time testing of the two CAN inputs comprises determining if a CAN transceiver connected to a bus line is correctly transmitting and receiving CAN data frames.
4 . The CAN Transceiver monitor according to claim 1 , wherein the ACK response circuit is configured to acknowledge the transmission of a CAN classic bus or CAN FD bus message/data frame via the acknowledge bit without having the CAN bus line connected to a main CAN bus line.
5 . The CAN Transceiver monitor according to claim 1 , wherein the ACK detection circuit and the ACK response circuit use counter logic.
6 . The CAN Transceiver monitor according to claim 5 , wherein a solution comprises a high-speed clock that allows the counter logic to operate faster than the CAN bit time, so as to know which bit is a bit time and, with that, deduce the current baud rate, thereby working as an auto baud-rate detector.
7 . The CAN Transceiver monitor according to claim 1 , wherein the ACK response circuit uses combinational logic combined with transistors, capacitors and resistors, the combinational logic being used to identify the latest rising edges of the signal in way to charge the capacitors that later are discharged in order to set the ACK bit.
8 . The CAN Transceiver monitor according to claim 7 , wherein the charge corresponds to the duration of an ACK response, so that, when it is time to acknowledge the frame, the ACK response circuit acknowledges the frame with the correct duration.