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broken

PostPosted: Sat Dec 14, 2013 3:14 pm
by markt12
I hooked up a test circuit to the 5volt pin 2 and ground pin 1. I was using the USB connection to my computer for the 5 volt source. Something was wrong with my test circuit and it was drawing too much current through the 2.2 ohm resistor. I smelled that smell and unplugged the USB connector, but the 2.2 ohm resistor burnt out like a fuse. No other connections were made to the EZSBC board. I replaced the 2.2 ohm resistor with a 5 ohm resistor, the closest value I could find. With nothing connedted to the EZSBC board except the USB connector, the board does not run. Before my accident, I could plug in just the USB connector, the serial port was detected, and teraterm would display the command menu. I could Run (R) a program and the 4 led's would blink on and off. This has happened twice, but most times now when I connect the USB connector to any USB port on my computer, the serial port is detected (port 7) the red LED blinks one time, and nothing happens on tera term no mater what keys I press.
Any ideas what I can try? Do you repair boards? The voltage on the USB port is 5 volts and the voltage on pin 2 is 4.68 volts.

Re: broken

PostPosted: Sat Dec 14, 2013 6:28 pm
by Daniel
Hi Mark

Sorry to hear about the misfortune on the board. Yes, I repair them if they died and the PCB is OK. Please measure the voltage on pin 40 and see if you find 3.3V and measure the voltage on pin 3, also 3.3V. If you have a scope, see that pin 40 is clean, no oscillation. I don't know if 5 Ohm is low enough. If you see a voltage below 3.3V on pin 40, hold down the Reset button and see if it increases. If it does then I will try adding another 5 Ohm on top of the one already on the board, that should fix things. If you are unsuccessful send me email and I will tell you how to return the unit. The fact that the USB is not detected by the PC is a bit worrying since it doesn't depend on the 3.3V regulator. Normally it is the last thing to die.

I read you post again and the fact that the red LED blinks when you plug the USB into the EzSBC1 is a good sign. It means that it passed its internal sanity check and that EzMon gained control. So I suspect you may have killed your USB cable. Try another one and look to see if the pins in the USB connector on the module. The USB to serial converter needs 5V to work properly and if the voltage drop over the 5V resistor is too large then the USB interface wont work. Measure both sides of the resistor that you replaced and let me know what you get.

The fact that the PC detects the serial port may mean that TeraTerm lost is configuration. Try reconfiguring the terminal as described in the 'Getting Started' doc.

Daniel

Re: broken

PostPosted: Sat Dec 14, 2013 7:25 pm
by markt12
Tera term flow control was none not x-on x-off as Getting Started showed. I changed that and saved the setup and everything seems to be working fine again!
Thank you!
Mark