![]() ![]() This daemon by default opens a connection to a CDC-ACM device (like a J-Link VCOM) as soon as the device has enumerated and starts sending AT commands over the device to the other side (usually a target MCU connected to J-Link). Many Linux distributions have the ModemManager application installed and running as a daemon by default. Even parity: Expected parity bit value: 0.Odd parity: Expected parity bit value: 1.Count of 1-bits in data is 4 (even), so expected parity bit:.Transferred data: 0x55 (b'0101_0101, data sent LSB first so starts with '1').Baudrate: 1 MBaud (2 bits per square in screenhots).The following setup is used for the partiy function test: by measuring the duration of a single high state. The speed VCOM is operating at can also be determined with an oscilloscope, e.g. The oscilloscope will show the same signal sequence for both, the Rx and the Tx pin, confirming the VCOM functionality. Use the letter " U" (01010101 in binary) to create a regular square-wave signal. Send data via VCOM using the given terminal application.Use an oscilloscope to visualize the signals sent via the Tx pin and the Rx pin.HTerm) and establish a connection to the COM port. Make sure pins VTref and GND are connected to J-Link.Create a loopback by connecting the Tx pin with the Rx pin.This leads to the Rx pin receiving the sent data meaning that VCOM is active and working. The VCOM functionality can be tested for by simply connecting the Tx pin with the Rx pin - creating a loopback that way - and starting a terminal application. Connected devices with VCOM functionality will be listed under " Ports (COM & LPT)". VCOM enable in J-Link Commander Checking VCOM stateĬhecking if VCOM is active can be done by opening the device manager. After that the device needs to be power cycled in order for VCOM to work. Start the J-Link Commander and enter " vcom enable". Under " Virtual COM-Port", choose " Enable" and click " OK". Start the J-Link Configurator and configure the device to enable VCOM functionality by double-clicking. Currently, only J-Link models listed on the following page marked with VCOM, support the VCOM feature: J-Link software and hardware features overview.Pin 5 = J-Link-Tx (out), Pin 17 = J-Link-Rx (in). VCOM can only be used when debugging via SWD target interface.In general, the VCOM feature can be disabled and enabled for debug probes which comes with support for it via J-Link Commander and J-Link Configurator. 3.1.2 Manually disabling ModemManager for specific USB devices.2.1 Testing VCOM functionality and speed.This will be a valid alternative procedure to verify the integrity of data being sent over the network to the UDS1100 being tested. Make separate TCP socket connections to each of the two UDS1100s and pass data from one open socket connection to the other and vice versa. they are connected to each other serially in identical 485 modes). This loopback test is possible only for UDS1100 set to RS485-4wire/RS422 mode.Īn option that successfully tests both RS485-4wire and -2wire modes is to use a UDS1100 connected serially to a second (known good) UDS1100.Ĭonfigure two UDS1100 units with the same RS485 mode settings and connect them serial to serial (i.e. a telnet client may be connecting to a raw TCP listener. If the data flow does not stop when the RS485-4w loopback connectors are disconnected from the UDS's serial port then there may be an issue with the network connection, i.e. It the echoed data is corrupt, garbled, or missing then there may be an issue with the device server's serial port. When the loopback wires are disconnected, no data gets returned or displayed on the terminal session when data is typed or sent into the session. When the loopback wires are connected you will see the characters you type displayed in the terminal window. ![]() To properly test the RS485 4 wire pins with a loopback on a UDS1100, disconnect both (+) and (-) wires from the terminals to verify that the loopback is or is not working. Optionally, you can send a text file that consists of known characters by clicking 'Transfer' -> 'Send Text File…'.In the Hyperterminal session, type a series of characters and verify that what you are typing is what appears in the Hyperterminal screen.Launch a Hyperterminal session, setting it up to communicate over Winsock (TCP/IP) directed to the UDS's ip address/port.Ping the UDS and verify that it responds.Loopback testing on a UDS1100 in RS485-4wire mode requires that Tx+ (pin 14) is jumpered to Rx+ (pin 21) and Tx- (pin 15) is jumpered to Rx- (pin 22).įig1: Loopback Connectors on UDS1100 DB25F DCE in RS485-4w/RS422 mode How can I test the RS485 4 wire pins with loopback connectors on my UDS1100? Can I do this for RS485 2 Wire, also?
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