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Documentation · Level Converter

Level Converter V5.0

The isolated serial interface is available in two variants, one for K-Line and one for RS485.

The interface has a galvanic isolation of min. 1kV and protects the PC Hardware from failures on the DUT side.

The K-Line is a bi-directional one wire bus mainly used in the automotive industry and specified by ISO9141 and ISO14230-1.

RS485 is a bus for differential serial data transmission and can be used over long distances and in electrically noisy environments.

Isolated serial interface PCB with RS232 D-Sub9, terminal block and K-Line / RS485 D-Sub9

Isolated serial interface, smaller PCB with one D-Sub9 and pin header

Chapter 1

Hardware

1.1Specifications

ParameterValue
Supply Voltage6V to 24V
RS232 IOssee SN65C3222
K-Line IOs2V to 30V; 0.5A to GND
RS485 IOssee SN65HVD1792D
Isolationsee Si8420BB and MEE1S0505SC
K-Line Baudrate200 KBaud specified by IRS but tested with up to 1.5 MBaud. See oscilloscope screenshots with 256 KBaud, 500 KBaud and 1 MBaud.
RS485 Baudrate1 MBaud specified by the RS485 Transceiver but tested with up to 3 MBaud. See oscilloscope screenshots with 1 MBaud, 2 MBaud and 3 MBaud.

1.2Absolute maximum ratings

ParameterValue
Supply Voltage-0.3V to 25V
RS232 IOssee SN65C3222
K-Line IOs-0.3V to 36V (see LM2903D)
RS485 IOssee SN65HVD1792D
Isolationsee SI8663BB and MEE1S0505SC

Exceeding the limits might damage the device.

1.3Connectors

1.3.1Terminal block

PinFunctionAlternativeDirectionComment
1VSupplyinput6 to 24V
2GNDPC

1.3.2D-Sub9 RS232 (female)

PinFunctionAlternativeDirectionComment
1
2RxoutputConnect with Rx from PC.
3TxinputConnect with Tx from PC.
4VSupply (jumper)input6 to 24V. Alternative for Supply Voltage if the terminal block is not used. A custom cable is needed.
5GNDPCConnect with GND from PC.
6DSRoutput
7RTSVSupply (jumper)input6 to 24V. Connect with RTS from PC. Alternative for Supply Voltage if the terminal block is not used. A custom cable is needed.
8CTSoutputConnect with CTS from PC.
9GNDPC (jumper)

1.3.3D-Sub9 K-Line / RS485 (male)

PinK-LineDirectionRS485Direction
1VBatinputTxpoutput
2LinputRxpinput
3Kinput/outputRTSpoutput
4GNDCTSpinput
5GNDGND
6VBatinputTxnoutput
7GNDRxninput
8GNDRTSnoutput
9GNDCTSninput

1.4Jumper configuration

1.4.1General

It is possible to use a custom RS232 cable with wires for VSupply (Pin 4 and 7) and GNDPC (Pin 9) to supply the PCB. To be able to use the Pins on the D-Sub9, the jumpers J1, J2 and J3 have to be set.

JumperNameComment
J1GNDPCPin 9 on RS232 D-Sub9
J2VS3Pin 4 on RS232 D-Sub9
J3VS2Pin 7 on RS232 D-Sub9. This is for backward compatibility only. Please use J2 if possible. The RTS signal is on this pin and may be used for the RS485 variant.

1.4.2K-Line

JumperNameComment
J1UBatt / VCCConfiguration for the pull-up voltage at the communication line. UBAT: Pull-up voltage is UBAT from the DUT. VCC: Pull-up voltage is 5V from the interface.
J2Single / DoubleConfiguration for single wire communication (send and receive on K-Line) or double wire communication (send on K-Line and receive on L-Line)

1.4.3RS485

JumperNameComment
J1180R terminating resistor from TxP to Txn
J2180R terminating resistor from RxP to Rxn
J3180R terminating resistor from RTSP to RTSn
J4180R terminating resistor from CTSP to CTSn
J510k resistor from RTSP to VCC
J610k resistor from RTSn to GND

1.5Order information

1.5.1PCB mounted on angle plate

  • Overall dimensions: 267mm x 36mm x 18mm
VariantOrder Number
Level Converter V5.0 variant K-Line118354
Level Converter V5.0 variant RS485118355

1.5.2PCB in the box

  • Dimensions of the box: 150mm x 80mm x 30mm
  • Overall dimensions: 154mm x 80mm x 30mm
VariantOrder Number
Level Converter V5.0 variant K-Line118229
Level Converter V5.0 variant RS485118353
Chapter 2

Signal Curves

2.1K-Line

Settings: VSupply = 12V; J4 to Single; J7 to VCC (5V); K bridged to L; transmission = 0x55

Oscilloscope capture: 256 KBaud on K
Image 1: 256 KBaud on K
Oscilloscope capture: 256 KBaud on RS232 Rx
Image 2: 256 KBaud on RS232 Rx
Oscilloscope capture: 500 KBaud on K
Image 3: 500 KBaud on K
Oscilloscope capture: 500 KBaud on RS232 Rx
Image 4: 500 KBaud on RS232 Rx
Oscilloscope capture: 1 MBaud on K
Image 5: 1 MBaud on K
Oscilloscope capture: 1 MBaud on RS232 Rx
Image 6: 1 MBaud on RS232 Rx

2.2RS485

Settings: VSupply = 12V; jumper on J8 and J9; Txp and Txn bridged to Rxp and Rxn; transmission = 0x55

Oscilloscope capture: 1 MBaud on RS485 Tx
Image 7: 1 MBaud on RS485 Tx
Oscilloscope capture: 1 MBaud on RS232 Rx
Image 8: 1 MBaud on RS232 Rx
Oscilloscope capture: 2 MBaud on RS485 Tx
Image 9: 2 MBaud on RS485 Tx
Oscilloscope capture: 2 MBaud on RS232 Rx
Image 10: 2 MBaud on RS232 Rx
Oscilloscope capture: 3 MBaud on RS485 Tx
Image 11: 3 MBaud on RS485 Tx
Oscilloscope capture: 3 MBaud on RS232 Rx
Image 12: 3 MBaud on RS232 Rx

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