Blink Sketch seems to Uploads, but on-board LED has random behavior

Hello

I start experimenting with an Arduino Pro-Mini. So I connected a FTDI to my PC and upload the blink sketch, via PORT 3 (I have confirmed that this is the corresponding PORT).

The think is that the on-board LED behaves randomly. For example, I upload the default 1000 msec delay, and I can see the LED blinking, with a period of 2 secs. When I change that value, making it smaller or bigger, the led is flickering and the light is very dim. Sometimes, if I disconnect the arduino board and reconnect it, the LED will work (with the "new" delay value), but after a while it "crashes" again and starts behaving strangely.

Any ideas on what causes this?

“the light is very dim” can have at least two reasons
1)
missing pinMode to set pin 13 as output; this however does not explain the flickering
2)
delay too short so it acts as a PWM and give reduced intensity; this could also explain the flickering

Neither of those reasons explains why it sometimes works and sometimes not and I don’t have an explanantion for that.

For example, I upload the default 1000 msec delay, and I can see the LED blinking, with a period of 2 secs.

That is normal for the blink sketch. The LED will be ON for 1 second, then OFF for 1 second.

When I change that value, making it smaller or bigger, the led is flickering and the light is very dim.

Can you post the modified code? There are two delay() instructions in the blink sketch, to change the blink time you need to change both of them to the new delay time, unless you want the ON and OFF time of the LED to be different.

I thought that maybe the current was too much for the usb hub that I am using, so I connect the FTDI directly to the motherboard. I tried to upload the default code of blink sketch and get the following error message

Arduino: 1.8.9 (Windows 10), Board: "Arduino Pro or Pro Mini, ATmega328P (5V, 16 MHz)"

Sketch uses 930 bytes (3%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x30
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x20
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x30
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x20
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x30
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x20
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x30
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x20
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x30
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x20
An error occurred while uploading the sketch

Now, I cannot even upload the code. It doesn't matter if I connect it to the MB or to the usb hub...

Check under Tools>Port in the IDE and see if you have selected the correct usb port, the port will change when you move the arduino to a different usb connector.

david_2018:
Check under Tools>Port in the IDE and see if you have selected the correct usb port, the port will change when you move the arduino to a different usb connector.

I have verified that port 3 is the right one with device manager - see attachment.
I am not sure that the port changes if I connect FTDI to a different usb connector.

Still I cannot upload anything and I get the same error message.

Now I am getting another message

Arduino: 1.8.9 (Windows 10), Board: "Arduino Pro or Pro Mini, ATmega328P (5V, 16 MHz)"

Sketch uses 930 bytes (3%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x0d
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x0d
Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

Capture.PNG

Just to close the topic.

It seems that I was unfortunate and the arduino was faulty out of the package. While trying to reestablish the connection with the pc I tried many different things and finally I switched to a new pro-mini and voilà, everything worked as it was suppose to.

I am not sure which exact component was faulty, but since I bought it for cheap it does not deserve any more time for fixing it.

Thanks

I'm glad to hear you have a working Arduino now. I would suspect a problem in the LED, or its drive circuit. I agree with you that it's sometimes best to move on with the fun and learning instead of getting bogged down trying to get a cheap board working. If you ever do feel like investigating it again, I would recommend connecting an external LED or multimeter to the pin 13 and seeing whether the "random behavior" also occurs there, or is limited to the onboard LED.