arduinointerfaceserialspiusb
I need to send 800 bytes of data from a computer to an arduino board every 20ms (approximately). I began with the serial library which works nicely but it is too slow even at its highest rate (115200 baud) for interfacing with a computer.
What other interfaces are available that can send at a faster rate? Can I use usb or spi? I can't seem to find libraries for these. I need something with about a 320 kBaud rate.
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Are there any shields that might be able to do this? Bluetooth or wifi?
This sounds like you might be having a baud rate mismatch. I have seen many cases where a device or library will default to a particular baud rate and wont be an issue until switching devices or platforms.
The other possibility is using a serial class that only works on linux.
Here is how I would suggest going about debugging this problem:-
Check the connections.. if you've mixed up signal ground and chassis ground (shield) you could get funny behavior just like you describe. Pin 7 on the DB-25 is the one you want to connect to DE-9 pin 5. I'll assume you're using a commercial adapter/cable or have one wired like this.
Maybe check the transmit out line to ensure it's idling at -12 ( < -3 anyway).
Make sure the instrument is set to RS-232, and not current loop (Jumper 7,8 and 1,2).
Try the most common serial port setting (9600/8-N-1), 9600 baud, NO parity, 1 stop bit switch 1, 2, 3 OFF switch 4, 5 ON switch 6 ON switch 7, 8 ON
Make SURE you understand which is 'OFF' and which is 'ON'. Don't laugh, I've seen this happen more than once, and some types of DIP switches are kind of ambiguously marked. If in doubt, an ohmmeter across the switch.. in fact you could check all of the switches to ensure they're working.
I like Realterm as a terminal program. It's free, and easy to change the parameters. Try it on something known working first of course, and look for an online tutorial. Really worth it.
If still gibberish after that, get a scope screen cap or photo and post it.
If you have a continuing need for a logic analyzer, this one is very cheap and relatively useful. Not as good as my Tektronix boat anchor, but this one will fit in a coat pocket. But I'd get a scope first if you don't have one. Even the worst scope is better than nothing.
Best Answer
How about only sending changed bytes each 20 ms? You'd need an additional 9 bits for addressing, but if you stuffed that bit in the empty bit in your 15-bit color data, you could do it with just one extra byte per LED. Depending on how fast your display is changing colors, that might work well. You could make a threshold, so if the color changes by less than X, you wait for the next round to send that data.
Or maybe try interlacing the data? Send even rows and odd rows in alternating sequence?
Or use 4 Arduinos in parallel?
Or control the LEDs through a shift register, and then send 15 bits to 15 Arduino pins via a parallel port (assuming you can find a PC with a parallel port)?