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February 21, 2010
News - Enginursday: The RedBot/M…
about 6 years ago
This $99 home use thing deserves a bump! Thanks Paul and Toni.
about 6 years ago
It wasn't this component's fault. It was the 3.3V line connected to the AREF pin of the Arduino. I didn't have the AREF pin set to EXTERNAL in the sketch, and so it was at 5V by default and actually driving my 3.3V bus up to 5V. The problem didn't occur until I ran a sketch that required this level converter, thus implicating the level converter, but the level converter is innocent.
This is a great little level converter. I'd pay twice the cost to have MOSFETs on the RX channels too. There's are also plenty of level shifter components that can handle many more channels; I would definitely pay for one of those on a breakout!
about 6 years ago
I had a high-current device on the same bus. Interestingly, a separate mistake was drawing the 3.3V bus to 5V, but when the high-current device was on the line, it was pulling too much current and bringing the bus back down closer to 3.3V. When I used the battery, which delivered more current, this didn't happen, and so the OpenLog would reset. Nasty problem. Fixed with a separate bus for that current-hungry component.
Somehow, this component is dragging my entire 3.3V bus up to 5V. Here’s the setup:
I’m only using one TX channel. The high side is 5V, and the low side is 3.3V. I bring the reset pin from an Arduino into the TXO channel on the high side (it should be held at 5V except to reset). I haven’t yet connected the TXI on the low side to anything. When I power on, my 3.3V bus is brought up to 5V! I’ve tested for a short; there is none. If I remove the component, my 3.3V bus is in fact 3.3V. Further, if I tie the TXI on the low side to ground via a 1kOhm resistor, I find that my 3.3V bus returns to 3.3V. I’ve also tested all of my connections; they’re good.
Does anyone have any idea what’s going on? Leakage current? Directionality?
This is working when using USB power, but not battery power. Setup:
5V Arduino's TX -> logic level shifter -> OpenLog's RX
OpenLog's TX -> resistor -> Arduino RX
Arduino's reset pin -> logic level shifter -> OpenLog's reset pin
The result is that, when the Arduino is powered off of USB, this logs fine. When it's powered off of a 11.1V LiPo battery (full charge) via the Arduino's barrel jack, the logger resets somewhat randomly about four times per second.
Can anyone see why this would happen?
For reference, the logic level shifter is the SparkFun BOB-08745.
I'm having a related problem. My code base is fairly large (47KB) and takes longer than 2 seconds to upload to the Arduino. The Arduino bootloader keeps RX held low during the upload, and therefore if my logger is attached to the board while I'm uploading to the Arduino, it goes into "emergency mode" and resets everything, even overwriting the config file stored on the disk! So now it's overwritten my config file back to 9600, my Arduino communicates with it at a different rate, so as a result of uploading new code to my Arduino, my disk is now storing files full of junk. To get around this, I'd have detach the Arduino from USB, remove the logger, attach to the Arduino and upload, detach USB, put the logger back in, and re-attach USB. And if I get it wrong? Now I have to add "manually edit the config file" to this list! The factory reset feature results in a lot of problems in completely normal use cases.
So now is my only other option to flash the OpenLog with new firmware?
about 6 years ago
I got it! Whew! Check this out: Nothing looked wrong, so I just started probing things. Turns out the terminal of R2 that should connect to pin 9 of the Venus (BOOT SELECT) was very slightly askew and was touching the capacitor next to it, unintentionally grounding it and pin 9. The data sheet says that's bad. I straightened it out with a solder iron and checked that pin 9 was no longer grounded. Then, I popped it back into a breadboard, and there was the serial output I had been waiting for! Seems to work fine now. It's getting a lock and reporting it correctly, and all is well in the world.
Thanks again for your support here, Mike. Other than this tiny manufacturing defect, this is an easy and much appreciated board.
Hi Mike. Thanks. I know it won't get a stable lock through the FTDI, but all I'm looking for at this point is some kind of serial output, even just empty NMEA sentences (I'll have a beefier power supply for the actual application). The LED is on (solid), the COM port is correct (I can talk to other things), and the TX->RX lines are going both ways. I contacted tech support as well. Any ideas what to try next?
Hi all. I'm having trouble getting any serial output from this board at all. Straight out of the box, I connected GND, 3.3V, TX0, and RX0 to a 3.3V FTDI, and I see no incoming serial at any baud rate. When I use the GPS Viewer, I set the appropriate port, 9600 baud, and click "Connect". However, nothing happens after this. If I click on any of the commands, it says, "Please connect to sky traq gps." Any ideas?
I just soldered up a TTL logic level shifter (the Sparkfun one), taking my 5V TTL on the Arduino side down to 3.3V on the OpenLog side, and now it's working. It looks like the 5V serial signal in fact is unacceptable to the ATMEGA, despite that the datasheet suggests it can accept 6V. Big debugging nightmare! Does anyone know any better way to do this?
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