CH32X033F8P6 UART Serial Output Not Working with CH340N USB-TTL Adapter

[jagadheeswarivenkata-lgtm]

I am using a CH32X033F8P6 board with the latest WCH Arduino Core.

My goal is to send UART data to a PC through a CH340N USB-to-TTL(UART) converter.

Hardware
MCU: CH32X033F8P6
USB-TTL: CH340N
Arduino IDE: (version)
WCH Arduino Core: (version)
Connections

CH32X033 TX pin → CH340N RX (HERE I USE ALL UART PINS)

CH32X033 RX pin → CH340N TX (HERE I USE ALL UART PINS)

GND → GND

Test Code 1:

HardwareSerial Serial2(USART2);

void setup() {
Serial2.begin(115200);
Serial2.println("CH32X033F8P6 ready");
}

void loop() {
static uint32_t count = 0;
Serial2.print("count: ");
Serial2.println(count++);
delay(1000);
}

Test Code 2:
Serial.begin(115200); / Serial1.begin(115200); / Serial2.begin(115200); with different bard rate also

but no UART data appears on the PC.

I already seen #145, #163, and other also

Verification

Same CH340N adapter works correctly with an Arduino Nano.
Baud rate is set to 115200 on the serial monitor.
TX/RX wiring has been checked multiple times.
GND is common between devices.
** My Question**
Which UART instance (Serial, Serial1, Serial2) is supported on CH32X033F8P6 in the Arduino core?
What are the exact TX/RX pins for each UART?
Is any pin remapping required?
Is there a known issue with UART output on CH32X033F8P6?

Any example code for UART transmission on CH32X033F8P6 would be appreciated.

[maxint-rd]

Have you also applied PR #171?
To get the correct pins working took some effort, but I eventually managed to support both dual and single serial port usage. Note that X035 board definition doesn't support dual ports and also doesn't have proper pinout support for the X033 TSSOP20.
My X033 board definition does some remapping to get things working. You can find a pinout diagram in my PR post and in the readme for the board definition.
I've not yet looked into serial over the USB pins (or anything else USB related).
PR #200 also includes this one, plus a bunch of V002/V006 variants.

So, serial output should work on the X033. 115200 should work fine on both ports, but I've only tested using the LinkE as serial to USB adapter, not with anything else.

[jagadheeswarivenkata-lgtm]

Hi,

I noticed that the CH32X035 is already included as a supported board in the WCH Arduino Core.

Since the CH32X033F8P6 is very similar in architecture, is there any reason it cannot be added in the same way as a fully supported board in the official core?

Would it be possible to integrate X033 support into the main Arduino core (like X035), instead of relying on separate PR-based board definitions and remapping?

We are planning to develop multiple projects using X033, so having official core support would be very helpful for stability and easier development.

Thanks.

[Saandeeparduino]

I noticed the same problem with the CH32X033F8P6 MCU. pinMode(), digitalWrite(), and digitalRead() are working well, but I still need to test the other basic Arduino functions.

I also tried using a CH340C module, but that wasn't possible. If @maxint-rd upgrades the Arduino core, I would be very happy because I really like this powerful chip from WCH. The Arduino core is still a bit limited, so it would be great if the other standard Arduino functions also worked with these boards.

I know this is a difficult task, and I really appreciate the effort involved. We are eagerly waiting for these improvements. Thank you for your hard work and support!

[maxint-rd]

Hello @jagadheeswarivenkata-lgtm

Since the CH32X033F8P6 is very similar in architecture, is there any reason it cannot be added in the same way as a fully supported board in the official core?

No, there is no reason. That "same way" is just what I did in PR #171. If you look into that PR, you can see what I needed to add to get the new board added to the menu. I basically added a variant that was based of the original X035 definition that was provided by WCH, using the vary same mechanism that WCH would use if they were to add another definition for a board variant. (If only WCH would merge that PR...)

We are planning to develop multiple projects using X033, so having official core support would be very helpful for stability and easier development.

Sorry; get ready to be disappointed... While WCH had a great start at this Arduino core; the approach seems to be to leave it up to the community to improve it. As far as I can see no WCH staff is assigned to support this core. The latest merge of a PR was over a year ago. The latest official release is more than 2 1/2 years old.

It seems this core is the product of a few dedicated employees who did this mostly in their spare time. From what I can see this core originates from the STM32 Arduino core, with most of the code just being copied as is. This allowed a very quick release of this OpenWCH Arduino core, right at the moment the 10-cent V003 CPU hype gained some traction. I'm still very thankful for the WCH people to have provided support as long as they did, because otherwise I would be limited to using much fewer and much more expensive MCU's for my Arduino projects.

@Saandeeparduino: I'm no WCH employee, yet fully on your side. Unfortunately, as just a community member I have no authorization to update this core. All I can do is submit PRs and respond to issues. Next to GPIO, I've successfully used other peripherals of the X033. I've added all the missing features for the X033 I needed for my personal projects. Just have a look at PR #171 and PR #200 to see what I've added. Maybe you can post a wish-list of features you still miss?

Personally, for several reasons, I really like the CH32 chip family and the Arduino eco-system. This motivates me to make my purchased chips as much usable as possible. I also like to share my work. (Still I would prefer WCH to either dedicate some staff, or to give active community members some authorization. At the moment all we can do is submit issues and PRs, but no new releases are expected. We can't even close resolved issues submitted by other people).

[jagadheeswarivenkata-lgtm]

Hello @maxint-rd,

Thank you very much for your support and your work on the CH32 Arduino core.

Following @jagadheeswarivenkata-lgtm's suggestion, we tested your CH32 core with the CH32X033F8P6. We successfully verified UART (Serial) communication using a CH340N USB-to-UART adapter at 115200 baud in the Arduino IDE.

Your work has helped us start development with the CH32X033F8P6. We really appreciate the time and effort you have put into adding support for this MCU.

We are planning to develop multiple projects using the CH32X033F8P6, and we would be happy to help by testing new features, reporting issues, and providing feedback whenever needed.

Thank you again for supporting the CH32 community!

[maxint-rd]

Hi @jagadheeswarivenkata-lgtm - You're welcome! Nice to see my name in the serial output!

Also good to see you eventually managed to get the CH340 USB connection working.
I'm still looking forward to do some testing of the direct usb interface. The CH32X033F8P6 has its USB peripheral on pins 5 and 6, so it should be possible to connect those directly to a USB connector without using an external CH340 chip. Unfortunately there are many more things on my wish-list and the amount of time I can spend is limited.

In PR #121 (followed by #127) some support for Adafruit TinyUSB mentions the CH32X035. If you have spare time, perhaps you can take a look at that to see if anything works for the X033 native USB port...

[Saandeeparduino]

T@maxint-rd,

Thank you very much for your continuous support and for all the work you have done on the CH32 Arduino core. Your contributions have been very helpful to the community.

My student @jagadheeswarivenkata-lgtm, his team, and I (@Saandeeparduino) are working together on this project.

We have started developing an Arduino-compatible board based on the CH32X033F8P6, called OpenRICE, by Vishishta Innovators. Our goal is to help school and college students learn embedded systems by building small projects using the OpenRICE board.

We also sincerely thank WCH for creating the CH32 MCU family and for providing the official Arduino core. We hope WCH will continue supporting and improving the Arduino ecosystem, as it will benefit many developers, students, and educators.

We will continue testing, sharing feedback, reporting issues, and contributing whenever possible.

Thank you again to both WCH and @maxint-rd for your valuable support!

[maxint-rd]

Excellent! Sounds like you're doing great work together! When I purchased the X033, my main reasons were because the TSSOP20 package has a similar layout as the V003 and it offers many features for a very affordable price. Compared to the V003 there are still some features that I have not worked with yet (such as USB).

One thing you need to check is the serial number. The first released series of the X033 has a fabrication error that prevents some features to be used. It cost me some headaches before I found out. Below the pinout diagram in PR #171. you can read this note:
*A3, VREF and hardware I2C don't work on CH32X033F8P6 0-series (lot number with the penultimate bit 5 being 0).
Of course I had the luck to receive those. My resolution was to use software I2C and an external voltage reference to determine VREF.

Overall the X033 is still a nice chip, but as with other CH32 family members, there will be some challenges on your way. The Arduino core lacks continued support from WCH, while the MounRiver IDE with the EVT package has a steeper learning curve, The CH32fun project is also interesting.

Another thing that I like to suggest you and your students is the interactive debugger in the Arduino 2.x IDE. Being able to do real time debugging was essential in the making of many of my additions.

For now I wish you all the best of luck. Have fun programming with CH32!

[Saandeeparduino]

Hi,

I have a question about the WCH MCU family.

Which WCH MCU series support UART serial flashing (uploading a .bin or .hex file directly over UART without using a hardware debugger)?

For example, does this work on any of these families?

CH32V003

CH32X033 / CH32X035

CH32V20x

CH32V30x

CH32F10x

If UART flashing is supported, could you please let me know:

Which MCU series support it?

Thank you!

[Saandeeparduino]

Finally, Successfully completed OpenRICE Board (CH32X33 F8P6)

[maxint-rd]

Very nice! Thank you for sharing this image,
I noticed the OpenRisc label. Are you by chance also sharing your designs? If so, perhaps you can post a link here?

[maxint-rd]

Which WCH MCU series support UART serial flashing (uploading a .bin or .hex file directly over UART without using a hardware debugger)?

For example, does this work on any of these families?
CH32V003
CH32X033 / CH32X035
CH32V20x
CH32V30x
CH32F10x
If UART flashing is supported, could you please let me know:

As far as I know, all chips with USB support have a factory bootloader that supports uploading firmware using the WCHISP tool. but I have no experience with it, since I always use the LinkE device.

The table below this Web Serial ISP gives an overview of the various family members and their boot loading capabilities.

I also encountered something called IAP, but haven't done anything with it. Perhaps this thread on EEV-blog gives a bit more information.

[Saandeeparduino]

Very nice! Thank you for sharing this image, I noticed the OpenRisc label. Are you by chance also sharing your designs? If so, perhaps you can post a link here?

Thanks! 😊

The current OpenRICE hardware design is available in my GitHub repository. It is still under active development, so there will be some changes and improvements before the final release.

Repository:
https://github.com/Saandeeparduino/OpenRISC-CH32X033F8P6-/tree/main

We are also planning OpenRICE V2, which will integrate an onboard programmer/serial debugger with the CH32X033, while also providing an external USB-to-UART interface for serial communication and programming.

Special thanks to @maxint-rd for the excellent Arduino core support, and to WCH for developing the CH32 MCU family. We also hope to collaborate with Vishishta Innovators to make OpenRICE a beginner-friendly, open-source development board for students and makers.

[Saandeeparduino]

Which WCH MCU series support UART serial flashing (uploading a .bin or .hex file directly over UART without using a hardware debugger)?
For example, does this work on any of these families?
CH32V003
CH32X033 / CH32X035
CH32V20x
CH32V30x
CH32F10x
If UART flashing is supported, could you please let me know:

As far as I know, all chips with USB support have a factory bootloader that supports uploading firmware using the WCHISP tool. but I have no experience with it, since I always use the LinkE device.

The table below this Web Serial ISP gives an overview of the various family members and their boot loading capabilities.

I also encountered something called IAP, but haven't done anything with it. Perhaps this thread on EEV-blog gives a bit more information.

Thank you! I understand now.

This information is very helpful for building OpenRICE V2. I'll explore the factory bootloader, WCHISP, and IAP options to see which approach is the best fit for making the board easier for beginners to use.

Thanks again for pointing me to these resources!