It just cost me more than an hour of troubleshooting when I tried to run the Serial1 connection of a MEGA 2560 China clone for the first time. It worked perfectly in a loopback mode (TX1-RX1 connected), but it didn't communicate with another modul as it should. I finally found the reason and I want to tell everyone who has the same problem with the same module to avoid my mistake:
My China MEGA 2560 simply has a wrong board labelling for the RX1 and TX1 pins! All other ports are labelled correctly, only the RX1 and TX1 labelling is interchanged, so that I did wrong connections.
The board I'm talking about is one of those they sell at AliExpress for some 6$, like this one: http://arduino-project.net/wp-content/uploads/2014/09/IMG-20140922-00441.jpg
Hope that helps someone!
That is interesting, looks like a defect in the labeling. That sort of thing may have had me pulling my hair out for more than an hour if I had that board!
I'm using a Chinese Mega and UNO, the RX and TX LEDS for USB COM port have their labels swapped as well. Simple program with Serial.print has the RX light flashing.
The problem is worse than just wrong labeling. I have an adafruit fona here, and trying to communicate over Serial1.
With a noname chinese "MEGA 2560" with ch340 USBchip and wrong labelling, it doesn't work at all. I have 2 of them, and both don't work.
With a chinese DCcduino MEGA 2560 with ch340 chip and wrong labelling, it works flakey. A lot of lost connections (every few seconds or so)
With a chinese sunfounder MEGA 2560 with mega16u2 USB chip and correct labelling, everything works fine.
Maybe the problem has to do with the ch340 chip?
Or bad routing on the PCB?
Or some undocumenteed pullup resistors or diodes?
Or bad soldering?
Enabling the internal pullup resistor on the arduino Rx pin with
pinMode( 19, INPUT_PULLUP );
does not make a difference.
Bad jumper cables are not the reason, because both the arduino mega and the fona are plugged into a adapter shield.
I've swapped the mega boards several times to make sure my results are consistent.
The power source is also not the reason - I've tried 2 different 5V sources.
Also the on board 5V regulator is not the reason, because I'm powering the arduino directly with 5V.
Does anybody have similar experiences?
Whatever the reason is - I don't have the time and resources at the moment to do the beta testing/quality check for the cheap chinese manufacturers. I will pay a bit more for the original megas in the future.
I'm also have USB download issues with my Cheap Chinese Mega 2560 clones. They were so cheap (~$10) I bought 5 of them.
I don't have any issues using the ICSP port to download them but of the two I've checked. One will sometimes download from the USB port (maybe 1 in 5 attempts). The other one will always fails a USB download (I think the USB->Serial is completely non-functional on the second one.
I've noticed these boards have the RX and TX LED's mislabeled. They have no brand name only "Made in China".
I've read somewhere that some Chinese clones have trouble resetting due to a missing capacitor from pin 13 of the CH340 to the 2560. The boards I have don't even have a trace that leads to anywhere from pin 13 of the CH340 which is likely why they have such trouble downloading.
It seems some companies are selling non-functional (or barely functional) boards for a really cheap price. I wouldn't be surprised if they know they are boards with problems; thus the extra cheap price.
Anybody know of some name brand Chinese clone Arduino's that work well?