Good day.
I recently bought this kit—it's an interesting product. I enjoyed soldering and assembling my own board. Unfortunately, the joy lasted only until I connected the board to the computer. The first problem: the board wasn't detected as a COM port, even via USB -unknown device. I solved this by installing the driver from the official Atmel website. Then, using Flip, I flashed the controller 16U2 with the original file from the Arduino folder—now the board is visible as a COM port. However, when trying to upload a sketch (a very simple Blink sketch), I got synchronization errors. Guided by the Arduino documentation, I ran a LoopBack test—the echo returns. I burned the bootloader to 328P using a second UNO R3—I thought maybe that was the problem. But no. The sketch uploads fine in IPS mode, it runs—everything works. I can't figure out where to dig next? Can anyone suggest anything?
I assume one of the LEDs is connected to D13 , so does it blink 3 times when you push the reset button?
If not then the bootloader is not there.
What type of USB cable are you using, USB-C to A or USB-C to C
Yes, 3 times blink is present when you push reset.
I used usb C to C and C to A - no difference (cable comes with UNO R4 wi-fi).
Remove the 328 from the socket and place a wire jumper between pins 2 and 3 of the socket, that will connect RX/TX right at the socket. Then run the loopback test again.
thank you in advance, I will try
Some additional info: I swapped 328P between two my UNO boards.. board with NOW issues (other UNO) works perfect with 328P (UNO DIY kit), but DIY one got the same issue.
Both the 328P and the 16U2 should have already been programmed.
Assuming you used the bootloader for the Uno, one possibility is that the RX/TX signals are not making it to the processor, possibly do to a bad solder joint or bad connecion in the socket. The test I described should eliminate that possibility.
Got, I will do it in 1 hour
One more thing : RX/TX channel LEDs show no signs of life at all when trying to upload a sketch.
Also, trying this code:
void setup() {
pinMode(13, OUTPUT);
Serial.begin(115200);
}
void loop() {
if (Serial.available()) {
int c = Serial.read();
digitalWrite(13, HIGH);
delay(30);
digitalWrite(13, LOW);
Serial.write((uint8_t)c);
}
}
D13LED was blinking very weakly... only if you looked closely, you could notice a weaker flicker.
Could be a whole diferent issue. If the loopback test worked and the booloader is there and NOT corrupted then it should work.
D13LED was blinking very weakly
It's only on for 30ms so it will appear dim.
Remember that when you use ICSP to upload a program, you wipeout the bootloader and it need to be re-burned
Hi @serhii13th.
Great work overcoming this problem!
When you perform an "Upload Using Programmer" operation, the bootloader is erased from the flash memory of the microcontroller. The bootloader is required in order to upload sketches to the board via a direct USB cable connection to your computer. Attempting to upload a sketch via the direct USB connection to the board when a bootloader is not present on the microcontroller is one of the possible causes of the upload failing with that error message you encountered.
For this reason, If you perform an "Upload Using Programmer" operation at some point and then later decide you want to go back to normal uploading to the boards, you must first perform a "Burn Bootloader" operation in order to be able to do so.
So try this:
- Connect the ISP programmer to the target board, just as you did before.
- Select Tools > Burn Bootloader from the Arduino IDE menus.
- Wait for the "Burn Bootloader" operation to finish successfully.
- Disconnect the ISP programmer from the target board.
- Connect the target board to your computer with a USB cable.
- Select Sketch > Upload from the Arduino IDE menus.
The upload should now finish successfully.
Thank you 
I will try now
Other than re-burning the bootloader and trying again, I'm out of suggestions for debugging.
Please provide a picture of the bottom of the board which is suitable to allow us to check the solder joints.
I checked via multimeter RX/TX from 328P to 16U2 -- looks like Ok..
Really have no clue what to check next
Maybe the 16u2 is not resetting the 328.
Does the L LED blink when you try to do an upload?
yes, but super weak blink if compare to manual reset (button)
also, I tried manual reset: capacitor between reset - ground, then button press when it starts uploading
