JTAG to Tag Connect

This PCB is an adapter that converts the 20 pin JLink connector to a 6-pin Tag Connect, much like this board. Ours, however, additionally contains an onboard LDO that can supply 3.3V to the attached device and the VTRef pin on the J-Link programmer so that it can program boards that are not self powered.

This most recent (nLine) version allows you to additionally power the target board with 5V and also select the whether to keep the I/O at the supply voltage or divide it down from 5V to 3V3. This allows powering higher voltage boards while still operating the MCU at 3V3 without on-board level shifters.

Interface

• Switch 1, labeled VSupply: Set to 5V to connect teh VCC pin on the TagConnect header (and the attached board) to the 5VC output from the JLink. Set to 3V3 to connect the VCC pin on the TagConnect header (and the attached board to be programmed) and the VTRef pin from the Segger JLink to the 3.3 V output from the regulator. Set to DEV to directly connect the VTRef pin on the JLink to the TagConnect VCC pin. This sets the I/O voltage for the JLink, but does not power the target board.

• Switch 2, labeled SWDIO: This switch can connect the SWDIO and !RESET signals, which is needed on some ICs. To leave the signals disconnected, leave the switch in the empty (down) position.

• Switch 3 labeled VIO: Set to Supply to use with I/O voltage same as VSupply. Set to 5V->3V3 to divide a 5V supply down to 3V3 for 3V3 I/O operation.

Troubleshooting

1. Blue LED does not come on when attached to JLink. You need to enable the 5 V output on the JLink:

    $ JlinkExe
    power on perm