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JeeNode Programming with CP2102

Added by DannyRitiu over 6 years ago

Hello, I have bought this cheap CP2102 USB to Serial converter: http://www.aliexpress.com/store/product/CP2102-Serial-Converter-USB-2-0-To-TTL-UART-6PIN-Module/812021\_569920657.html
The problem is that I can’t make them work.
I did the following things:
- I connected the CP2012’s DTR pin to the JeeNode’s DTR
- I removed (short circuited) the capacitor between the DTR pin and the Atmel328P’s pin no.1 (C1 on JeeNode)
But it still doesn’t work. I tried many baud rates and many configurations.

Do you think the programmer is broken or is it not compatible? Or should I do anything else to make it work?

Help me figure this out and I promise to make a complete tutorial if I succeed.

Thank you!


Replies (8)

RE: JeeNode Programming with CP2102 - Added by martynj over 6 years ago

Have you checked the output voltage levels (from the convertor to the JeeNode)? USB power is 5v, the Jeenode expects 3.3v for logic ‘High’. Without some limiting resistor, you risk damaging I/O pins on the AtMega if that convertor is set to 0-5v logic levels.
There is some mention of this issue in the Wiki for the USB-BUB II http://shop.moderndevice.com/products/bub\_ii

RE: JeeNode Programming with CP2102 - Added by DannyRitiu over 6 years ago

Yes, I have checked. The voltage level on the USB/TTL adapter’s RX and TX pin is 3.3V constant. It doesn’t change. I tried to open Arduino Serial Monitor and tried to send some data, but nothing changes. The voltage level is always 3.3V.

So I’m guessing the IC is damaged. What do you think?

RE: JeeNode Programming with CP2102 - Added by martynj over 6 years ago

The adapter RX & TX pins are constant 3.3v with the JeeNode disconnected?

RE: JeeNode Programming with CP2102 - Added by DannyRitiu over 6 years ago

Yes, that’s correct

RE: JeeNode Programming with CP2102 - Added by martynj over 6 years ago

It is difficult to diagnose the problem further without a schematic of the board.
Note that the DTR signal is needed - it passes via the capacitor on the JeeNode to the RESET pin. Without that signal, the JeeNode bootstrap process will not start.  For testing, you can temporarily ground the reset pin with a jumper to get the same effect.

RE: JeeNode Programming with CP2102 - Added by DannyRitiu over 6 years ago

Hello, yes, I know that the DTR signal is needed, but still I can’t program the JeeNode. I can program it with an USBasp but not with CP2102.

I checked the schematic with the CP2102 manufacturer and it is correct. My biggest question is that is it normal to have constant 3.3V on the RX/TX pins? Even if there is only small amount of communication I shouldn’t have 3.3V, should I? Specially on RX pin… it is really disturbing.

If a schematic can help you, you can find my converter’s schematic in this PDF: http://www.silabs.com/Support%20Documents/TechnicalDocs/CP2102-9.pdf
on page 14.

Thank you for trying to help me… Best regards,

RE: JeeNode Programming with CP2102 - Added by martynj over 6 years ago

Hopefully the PCB traces are visible on the adapter. Since the CP2102 implements a full set of UART control signals, some of these need forcing to “TRUE” before RX/TX can become active. (DCD, DSR, CTS).   These pins may be hardwired “HIGH” and/or appear at the edge connector.  

RE: JeeNode Programming with CP2102 - Added by dzach over 6 years ago

I have a CP2102 running with a JeeNode fine. Mine was even cheaper than the one in your link; the DTR signal was not brought out and I had to solder a wire to that tiny SMD IC, as shown in the first picture. You can see how I have them connected by following the wire colors in the pictures. To make room for the DTR wire I disconnected the RST signal from the C2102 connector and connected the DTR instead (yellow color).

To answer your question, yes, the combination of JeeNode and CP2102 works fine with only the 3.3V pin connected. As you can see in the pictures, the 5V pin (blue color) is not connected on the C2102 connector.

EDIT:
RXD and TXD are connected straight, not crossed.

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