FTDI/usb connection not working

[eriknauman]

I can’t upload sketches to the backpack. The backpack and 16X32 matrix are working, running the preloaded sketch. I have the FTDI cable from Tinkersphere, and I rearranged the pins to match the Adafruit cable, so from 1-6 they go GND, CTS, 5V, TX, RX, RTS. I already had the most recent FTDI VCP driver but reinstalled it anyway. I’m on Mac OS 10.10.5, using Arduino IDE 1.6.4. In Tools I have selected Arduino UNO and the USB serial port. The matrix turns off when I start uploading, then resets and the error is avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
I don’t know what else to try, any ideas?
Thanks, Erik

[Michael]

Your wiring sounds right. If the board is running, then the Uno bootloader is definitely there. And it sounds like the reset is working. It must be an issue with the cable or your driver. I use a Mac, though, and have no issues.

In my experience, when it comes to FTDI cables, the cheap ones are no good. I have experienced 50% failure rate when sourcing cheap or “oddball” ones (wrong pinouts!). This is why I ONLY sell genuine FTDI manufactured cables or adapters that I know work (e.g. the Adafruit FTDI friend). There are many counterfeit FTDI chips in the world, and they are installed in cheap cables.

[eriknauman]

I just did some tests on the cable, following this http://www.ladyada.net/wiki/ftditest, and all pins checked out good except the TX pin measured 2.7v instead of 3.3v. Could that cause a problem with the serial comm?

[Michael]

Yes, that could certainly cause a problem. The voltage is not high enough to register with the 5V logic on the ATmega328 microcontroller.

You could also check the soldering connections to make sure the RX and TX pins on the header are connected to the microcontroller. See this image for the traces:
http://nootropicdesign.com/matrixbackpack/design.html

[eriknauman]

So I ended up using this serial adapter from Tinkersphere: http://tinkersphere.com/electronic-components/803-ft232-serial-module-ftdi-helper.html. It was weird I checked the voltage level on the TX pin on a number of their FTDI cables and all were in the range 2.8-3.0 and wouldn’t successfully upload a sketch. But this adapter works so I’m happy.

[Michael]

OK, good to hear. When it comes to FTDI cables and adapters, it really does pay to use more expensive, official devices. Cheap stuff fails a lot.

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