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This tutorial is designed to help you build a bare metal debugging and development environment for Sipeed Maix Bit (Kendryte 210).

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Tutorial of Building Bare Metal Debugging & Development Environment for Maix Bit (K210)

Notice that the Environment here is for C/C++, Assembly, Bare metal, not for MaixPy.

English | 简体中文

Objective for the Tutorial

This tutorial is designed to help you build a bare metal debugging and development environment for Sipeed Maix Bit (Kendryte 210). The tutorial will guide you step by step without basic knowledge of embedded system and try to reduce uncontrollable bugs.

Advices

Please strictly follow every step of the tutorial since every step of the tutorial has a quite reasonable reason to avoid some crazy mistakes.
Please ensure that you have basic knowledge of electronic circuit, Linux (operating system), GCC & GDB (C/C++) before starting the tutorial.

Hareware Preparation

Connection

The pin layout of debugger:

The pin layout of Maix Bit:

Connection table:

Debugger Maix Bit
GND GND
RXD TX
TXD RX
5V 5V
3V3 3V3
TDI TDI
RST RST
TMS TMS
TDO TDO
TCK TCK

Notice that Debugger's RX pin should be connected to Board's TXD pin, and Debugger's TX pin should be connected to Board's RXD pin. This is important for UART for Serial Communication.

Development Environment

Host: Windows 10 Build 19042.685
Virtual Machine: VMware Workstation 16 Player (VirtualBox has some tricky things on USB)
System image: ubuntu-20.04.1-desktop-amd64.iso (Use desktop version to use multiple terminals and VS Code easily)

We did not choose WSL2 here because of WSL #2195. WSL2 is using Hyper-V, but Hyper-V does not support USB pass-through.
Alternative Solutions:
1. OpenOCD on Windows, ToolChain on WSL2
2. Use usbip-win, OpenOCD use IP access USB device
3. Similar to 2, usbipd-win has provided an "official" workaround, see Connecting USB devices to WSL
Just do yourself a favor, use VM :)

Prepare Development Environment Steps

Recommend Step for creating a working directory (optional):
mkdir k210 && cd k210

ToolChain Installation

  1. Download Kendryte ToolChain Release v8.2.0
  2. tar -xvzf kendryte-toolchain-ubuntu-amd64-8.2.0-20190213.tar.gz
  3. cd kendryte-toolchain-ubuntu-amd64-8.2.0-20190213/kendryte-toolchain
  4. sudo cp -a ./. /opt/riscv-toolchain, the ToolChain is copied to /opt/riscv-toolchain, notice that the folder name is riscv-toolchain instead of kendryte-toolchain !
  5. export k210toolchain=/opt/riscv-toolchain/bin, export PATH="$k210toolchain:$PATH", add ToolChain to path.
    Now, ToolChain Installation has finished.

About ToolChain: https://metalcode.eu/2019-11-16-gnu-toolchain.html

SDK Installation

  1. Download Kendryte SDK Release v0.5.6
  2. tar -xvzf kendryte-standalone-sdk-0.5.6.tar.gz
  3. cd kendryte-standalone-sdk-0.5.6
  4. mkdir build && cd build
  5. cmake .. -DPROJ=<ProjectName> -DTOOLCHAIN=/opt/riscv-toolchain/bin && make
    Notice that <ProjectName> needed to be replaced by real Project Name (hello_world).
    Now, SDK Installation has finished, and hello_world should be compiled successfully in build.

If riscv64-unknown-elf-gcc: error trying to exec 'cc1': execvp: No such file or directory occurs, recheck ToolChain Installation steps to make sure (1) you have /opt/riscv-toolchain & (2) you have added ToolChain location to $PATH.

OpenOCD Debug

Notice that Maix Bit uses CH552 chip to implement USB-Serial without JTAG. (K210 supports JTAG, but the CH552 on Maix Bit has no JTAG function) (https://wiki.sipeed.com/soft/maixpy/en/get_started/install_driver/bit.html)
CH552 emulates FT2232 chip, which is the same as the debugger chip (FT2232C) and causing conflict if they are used at the same time.

ONLY connect the debugger to your VM to avoid conflict!

  1. Download Kendryte OpenOCD Relaese v0.2.3
  2. tar -xvzf kendryte-openocd-0.2.3-ubuntu64.tar.gz
  3. cd kendryte-openocd-0.2.3-ubuntu64/kendryte-openocd
  4. cd bin
  5. ./openocd -f ../tcl/kendryte.cfg

If ./openocd: error while loading shared libraries: libusb-0.1.so.4: cannot open shared object file: No such file or directory occurs, run sudo apt-get install libusb-0.1 ;
If ./openocd: error while loading shared libraries: libftdi.so.1: cannot open shared object file: No such file or directory occurs, run sudo apt-get install libftdi-dev ;
If ./openocd: error while loading shared libraries: libhidapi-hidraw.so.0: cannot open shared object file: No such file or directory, run sudo apt-get install libhidapi-hidraw0 .
See https://github.com/ntfreak/openocd/blob/0dd3b7fa6c7930446967772832a351e90c426d69/README#L221

  1. Then, you should see

     _  __              _            _     
    | |/ /___ _ __   __| |_ __ _   _| |_ ___  
    | ' // _ \ '_ \ / _` | '__| | | | __/ _ \ 
    | . \  __/ | | | (_| | |  | |_| | ||  __/ 
    |_|\_\___|_| |_|\__,_|_|   \__, |\__\___| 
                               |___/          
    Kendryte Open On-Chip Debugger For RISC-V v0.2.3 (2019-02-21)
    Licensed under GNU GPL v2
    adapter speed: 3000 kHz
    Error: No J-Link device found.
    

    If you are not using J-Link Debugger, you will see the error. It is okay, we just check the correctness of OpenOCD installation here. You can Ctrl+C to exit.

  2. By https://steward-fu.github.io/website/mcu/k210/openocd.htm & https://metalcode.eu/2019-11-19-k210-debugging.html & https://mensi.ch/blog/articles/using-the-sipeed-jtag-debugger-with-a-blue-pill,

    first, cd ../tcl

    • create file ft2232c.cfg
    interface ftdi
    ftdi_vid_pid 0x0403 0x6010
    
    # [3:0] = [TMS 1, TDO 0, TDI 1, TCK 1]
    # [7:4] = GPOPL0-3
    # [11:8] = GPOPH0-3
    # 0xfff8 = 1111 1111 1111 1000
    # 0xfffb = 1111 1111 1111 1011
    ftdi_layout_init 0xfff8 0xfffb
    
    ftdi_layout_signal nTRST -data 0x0100 -oe 0x0100
    ftdi_layout_signal nSRST -data 0x0200 -oe 0x0200
    • create file k210.cfg
    # debug adapter
    source [find ft2232c.cfg]
    
    transport select jtag
    adapter_khz 10000
    
    # server port
    gdb_port 3333
    telnet_port 4444
    
    # add cpu target
    set _CHIPNAME riscv
    
    jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x04e4796b
    
    set _TARGETNAME $_CHIPNAME.cpu
    target create $_TARGETNAME riscv -chain-position $_TARGETNAME
    
    # command
    init
    halt
  3. cd ../bin
    Again, confirm you are in kendryte-openocd/bin.
    Just run ./openocd -f ../tcl/k210.cfg. (Debug -d)
    If

    Error: libusb_open() failed with LIBUSB_ERROR_ACCESS
    Error: libusb_open() failed with LIBUSB_ERROR_ACCESS
    Error: no device found
    Error: unable to open ftdi device with vid 0403, pid 6010, description '*', serial '*' at bus location '*'
    

    occurs, run sudo ./openocd -f ../tcl/k210.cfg.

    Now, OpenOCD will connect successfully and shows something like:

     _  __              _            _     
    | |/ /___ _ __   __| |_ __ _   _| |_ ___  
    | ' // _ \ '_ \ / _` | '__| | | | __/ _ \ 
    | . \  __/ | | | (_| | |  | |_| | ||  __/ 
    |_|\_\___|_| |_|\__,_|_|   \__, |\__\___| 
                               |___/          
    Kendryte Open On-Chip Debugger For RISC-V v0.2.3 (2019-02-21)
    Licensed under GNU GPL v2
    adapter speed: 10000 kHz
    Info : ftdi: if you experience problems at higher adapter clocks, try the command   "ftdi_tdo_sample_edge falling"
    Info : clock speed 10000 kHz
    Info : JTAG tap: riscv.cpu tap/device found: 0x04e4796b (mfg: 0x4b5 (<unknown>), part: 0x4e47,  ver: 0x0)
    Core [0] halted at 0x8000b434 due to debug interrupt
    Info : Examined RISCV core; found 2 harts
    Info : Listening on port 3333 for gdb connections
    Core [1] halted at 0x8000bf8e due to debug interrupt
    Core [0] halted at 0x8000b434 due to debug interrupt
    Info : Listening on port 6666 for tcl connections
    Info : Listening on port 4444 for telnet connections
    

    be sure there is Core [0] and Core [1] . Also, notice that we will use port 3333 in GDB for debugging later.

GDB from ToolChain for Debug

Start a new terminal here and keep the old OpenOCD terminal!

  1. cd kendryte-toolchain/bin

  2. ./riscv64-unknown-elf-gdb ../../kendryte-standalone-sdk-0.5.6/build/hello_world

  3. In (gdb):

    1. set print pretty on (optional)
    2. target remote localhost:3333
    3. monitor reset halt
    4. load
      Debug: tb (tbreak) main
    5. c (continue)
      Debug: s (step) (step into) n (next) (step over)

    (If hello_world is debugging, the program will be stuck in scanf() and will not print anything by printf(). To solve this issue, we need to use UART for Serial Communication)

  4. Any time, Ctrl+C will stop current debugging. Then, q (quit) in (gdb) can quit gdb.

About OpenOCD and GDB debug:
https://stackoverflow.com/questions/38033130/how-to-use-the-gdb-gnu-debugger-and-openocd-for-microcontroller-debugging-fr

UART for Serial Communication

Start a new terminal here and keep OpenOCD terminal and GDB terminal alive!

Arguments are from k210 UART Doc p118:

Arguments for UART:  
    Baud Rate(Bps): 115200 (9600 no working!)  
    Parity: None  
    Data bits: 8  
    Stop bit: 1

If you are in Linux, you do NOT need a driver. If you are in Windows, download CDM21228_Setup.zip for Win10, download FTDI_Win7.zip for Win7 from https://dl.sipeed.com/MAIX/tools/ftdi_vcp_driver.

If you are following OpenOCD Debug and only connecting debugger to your VM, just go to Step 1.

If you are using Maix Bit's ft2232c chip for USB-UART (on your host):
Notice that Maix BiT's CH552T chip only use ONE serial interface of K210 to implement USB-Serial.
Thus, two serial interfaces will be shown in device management, but only one can be used for UART so you need to try both! (https://wiki.sipeed.com/soft/maixpy/en/get_started/upgrade_maixpy_firmware.html)

  1. sudo apt-get install minicom
  2. ls /dev/ttyUSB* -la
    remember the device name: (for example) ttyUSB1

    When the debugger is just connected to VM, there may be two ttyUSBs (like ttyUSB0 and ttyUSB1). If OpenOCD is running, there should be only one ttyUSB available.

  3. sudo minicom -s -con (Colorful screen -con)
  4. select Serial port setup
  5. press A, change device to the device in 1. , for example, /dev/ttyUSB1
    press F, set to No (Important!)
    press Enter
  6. select Modem and dialing
    press the corresponding keys and set 9 strings Init string, Reset string, Dialing prefix #1, Dialing suffix #1, Dialing prefix #2, Dialing suffix #2, Dialing prefix #3, Dialing suffix #3, Hang-up string to nothing.
    press Enter
  7. select Screen and keyboard
    press B, set to DEL
    press R, set to Yes
    press Enter
  8. select Save setup as dfl (Save the current setup as default)
  9. select Exit from Minicom
  10. sudo minicom
    Now, you should see
    Welcome to minicom 2.7.1
    
    OPTIONS: I18n 
    Compiled on Dec 23 2019, 02:06:26.
    Port /dev/ttyUSB1, 08:31:02
    
    
    Port /dev/ttyUSB1 is connected.
    Notice that press Ctrl+A first, then Z for help or any key for other function, not press them simultaneously.
  11. If you are debugging hello_world in gdb with OpenOCD, and type 6 in minicom.
    Then, you should see
    Welcome to minicom 2.7.1                                               
                                                                   
    OPTIONS: I18n                                                          
    Compiled on Dec 23 2019, 02:06:26.                                     
    Port /dev/ttyUSB1, 03:12:01                                            
    
    Press CTRL-A Z for help on special keys                                    
    
    Core 0 Hello world                                                         
                      Core 1 Hello world                                       
                                        6                                      
    Data is 6                                                              
    
    
    Now, UART should work well.

MaixPy bin should be burned to Maix Bit by default. If Maix Bit's UART is connected correctly, press the RESET button on Maix Bit, and you should see something like

About Minicom setup:
https://maixpy.sipeed.com/en/get_started/serial_tools.html?h=115200
https://wiki.emacinc.com/wiki/Getting_Started_With_Minicom

About

This tutorial is written when I only have the experience of using development board but have no knowledge of embedded development. In fact, it is mainly for building an on-chip verification environment for my compiler project about RISC-V assembly.

Now (2020.12), there are not many resources of RISC-V development board, which means we need some exploration during development, especially for non-MaixPy development environment of Maix Bit. I hope this tutorial can help more people enjoy the fun of RISC-V bare metal development :)

Acknowledgement

@steward-fu (Steward Fu):
https://steward-fu.github.io/website/mcu/k210/openocd.htm
@metalcode-eu (Metalcode):
https://metalcode.eu/2019-11-19-k210-debugging.html
@mensi (Manuel Stocker):
https://mensi.ch/blog/articles/using-the-sipeed-jtag-debugger-with-a-blue-pill

License

Copyright (C) 2020-2021 Qingpeng Li
This work is licensed under a Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License.