RV-LINK

RV-LINK--emulator, the GD32VF chip becomes an emulator after burning the RV-LINK firmware, and can be connected to the external chip through the JTAG pin

Official related address: https://gitee.com/zoomdy/RV-LINK

Next, we will introduce the emulator, its circuit and firmware download steps. All relevant information will be placed in the attachment.

brief introduction:

• The goal of RV-LINK is to make a RISC-V emulator, but the RV-LINK project does not include hardware. RV-LINK writes firmware for existing RISC-V development boards. Development boards with RV-LINK firmware burned can be used as Emulator usage

What is different from other emulators is that RV-LINK interacts directly with GDB through the USB serial port and does not require an intermediary such as OpenOCD.

• Among the hardware officially provided by RV-LINK, the smallest one is Longan Nano, which is the smallest system board with GD32VF103 chip, as shown in the figure below:

        It is used to learn the GD32VF series with RISC-V as the core. It can also be used as an emulator after burning RV-LINK firmware. Of course, the chips it can debug are limited to the GD32VF series.

        As a minimal system, Longan Nano is small and exquisite, including LCD, SD card, etc., and is fully equipped. However, if used as an emulator, it is slightly complex, contains relatively many components, and is large in size. Looking at its schematic diagram, it not only contains the components required for the minimum system, but also includes the FPC socket, SD card slot, and an extra LDO circuit to power the LCD. These are relatively a waste of resources. .

        In terms of price, you can buy it on Taobao for about 25 yuan. If you make one yourself, thanks to Jialichuang’s 5 yuan advantage in making boards, about 10 yuan is enough.

• In terms of application, the purpose of making it is to apply it to a small GD32VF development board I made, which will be open sourced later. The Longan Nano is larger than the desired range, so I made one myself.
• Of course, in actual production, only the power supply, minimum system circuit, buttons, indicator lights, pin headers, etc. need to be retained. The schematic diagram can directly use part of the Longan Nano schematic diagram with slight changes. Let’s briefly talk about the circuit content. :

• The interface still uses type-c. It inputs 5V and reduces the voltage to power the board. At the same time, it is connected to the USB pin of the chip to transmit signals. Since no external clock is needed, the 8MHz crystal oscillator can be retained. It contains two buttons: BOOT0 & NRST. Control the chip operating mode, use the status indicator light for status indication, and lead out the required pins. The Longan Nano schematic will be placed in the attachment.

Firmware burning steps:

In the link given at the beginning, the official has given a detailed description, and I intend to re-explain it here:

• First, you need to download a GD32 MCU Dfu Tool. Its download link is in the document given above, but what I encountered is that the link cannot be opened and can only be obtained through other methods. For convenience, I will place it in In the attachment, unzip it after downloading. There are two directories in it:

1. GD32 MCU Dfu Drivers
2. GD32 MCU Dfu Tool

Depending on whether your system is 32-bit or 64-bit, select x86 or x64 in the GD32 MCU Dfu Drivers directory. Our computers are generally 64-bit, so just select X64. To install GD32 MCU Dfu Drivers.exe, you must open it with administrator rights . Otherwise, the installation will fail.

Click Install to install. GD32 MCU Dfu Tool does not require installation.

• Then download the firmware applied to the Longan Nano development board: longan-nano-xxx.hex and put it in the attachment.
• Press and hold the BOOT0 button, then press the RESET button, release the RESET button, and finally release the BOOT0 button to enter DFU mode
• Open the GD32 MCU Dfu Tool/GD32 MCU Dfu Tool.exe software. This does not require installation. Click the open button, select the RV-LINK firmware (longan-nano-xxx.hex) downloaded earlier, and then click the OK button to start updating the firmware.

• After the firmware update is completed, press the reset button to reset. You can observe that the LED emits short pulses (on for 100ms, off for 900ms), waiting for GDB to connect, and you can start debugging.