J-Link-OB-K22-SiFive
This article describes specifics of the J-Link OB K22 SiFive.
Contents
Debug interface
VCOM support
The J-Link-OB-K22-SiFive supports 2 VCOM ports that are accessible from the host (PC) side.
Pin usage
On the J-Link OB side, the following pins are used for VCOM:
VCOM0
- PTB16 (J-Link Rx)
- PTB17 (J-Link Tx)
VCOM1
- PTC1 (J-Link RTS)
- PTC3 (J-Link Rx)
- PTC4 (J-Link Tx)
- PTC5 (J-Link DTR)
RTS behavior
The RTS line of J-Link is used to reset the ESP32 WiFi device on the eval board the OB is mounted on. It has an active LOW logic. The pin may be controlled from the host side for example via Python calls. The following behavior was explicitly requested by SiFive to make the J-Link OB mimic the behavior of simple USB to serial dapaters:
| Python call | Physical RTS level |
|---|---|
| xxx | xxx |
| xxx | xxx |
TBD
DTR behavor
TBD
WebUSB support
The J-Link OB K22 SiFive supports WebUSB for firmware build compiled Jul 30 2019 12:24:12 (delivered with V6.48a of the J-Link software) and later. By default, WebUSB support is not enabled on the Ob and needs to be enabled per one-time setup. In the following, it is assumed that it is already known what WebUSB is and what it can be used for. For more information, please refer to the WebUSB wiki article.
Enabling WebUSB
In order to enable WebUSB, J-Link Commander needs to be started and the "WebUSBEnable" command needs to be executed:
After power-cycling the J-Link OB, it will be listed as a WinUSB device in the device manager:
