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16  Using Arduino / LEDs and Multiplexing / Re: Driving Multiple WS2801 LED Strands Quickly on: November 25, 2013, 02:47:07 am
It's probably not going to be faster, and not worth pursuing unless you absolutely must have them synchronized. Here's why. The WS2801 is a clocked shift register input, so it's much more relaxed than the WS2811 for bit timing. So you're hoping that you can just present the current bit for all of the strings, possibly as a port write instead of a pin write....that would make sense, if that was all you had to do. In order to prepare the bits for transmission, you still need to increment through each of the output bytes, do the bitshift, grab the bit you want, and store it into a variable that you'll write to the port later. It ends up being almost the same amount of cycles to do all that preprocessing, versus just doing a normal SPI write.

Here's one way to gain a lot of speed. Use the SPI hardware output peripheral, and set up a demux IC to aim the SPI clock output at one of the strips. Then you just drop a byte into the SPI register, let the hardware do the sending, aim the demux at another strip, and fire away. Probably 100% speedup over a software-only approach.
17  Using Arduino / Project Guidance / Re: Serial communication problem on: October 28, 2013, 02:17:16 pm
Please note that the mini-USB port is connected to an FTDI converter, which has RX and TX pins connected to the Arduino's RX and TX pins. So when you attempt to use the Arduino USB serial monitor along with something else on the RX and TX pins, you'll see conflicts. It's absolutely no surprise that code download would be a problem with the motor controller also attached to those pins.
18  Using Arduino / Project Guidance / Re: arduino as serial client? on: October 28, 2013, 02:13:27 pm
The Arduino is currently using serial over USB, but what you want is RS232 (which is more of a communication voltage standard as applied to serial comms). The TTL-serial data from your Arduino needs to be converted to RS232 levels, which is something like +/- 9 to 12 volts. Usually, people use a MAX232 chip (or compatible, they're cheaper) which is designed for this exact purpose. It would require soldering up a PCB with some capacitors etc. But there are premade shields for this, Sparkfun has one: https://www.sparkfun.com/products/11958

However, you'd need to remove that shield in order to program the Arduino through USB. There may be other shields out there that allow you to switch the RS232 connection on and off, or let you tie to other pins and use SoftwareSerial instead of the hardware ports.

Once you have the electrical side of things figured out, the rest is easy...just use some the Arduino serial examples. A "Serial.println("get ip");" might be your start.
19  Using Arduino / General Electronics / Re: Using Microchip MCP2200 instead of FTDI FT232 on: October 18, 2013, 02:09:15 pm
I can see why you would want to be able to control the GP pins from the USB side, for things like MCU hard resets - but to make them uncontrollable from the UART side seems madness...

Madness? THIS. IS. RS232.

It's a byte pipe. USB is able to control the GPIO pins because it sees the FTDI device as a structure with various elements, just one of which is a serial data link. On the uC side, it's just a hose containing bytes, there's no method for out-of-band signaling of other functions. Would you want the FTDI chip to contain some magic sequence of bytes that triggers the GPIO? What if in the course of transferring other data, that magic sequence occurs? Not a good idea.
20  Using Arduino / General Electronics / Re: Using Microchip MCP2200 instead of FTDI FT232 on: October 17, 2013, 03:51:19 pm
I can confirm that the FT230X works fine for Arduino programming, with no configuration needed. DTR support works fine. It's what I use on the LED Shades. Keep in mind that it is a 3.3V part, though.

The last I heard about the MCP2200, it didn't have correct support for the DTR line, at least in the Windows drivers...the Windows CDC driver left much to be desired, and that's what the MCP2200 leverages (the FTDI chips use their own VCP driver). Things may have improved since then.

Edit: Actually, I'm using the RTS line, not the DTR line. That works because so many FTDI adapters (including FTDI's own cables) broke out the RTS line instead of the DTR line. Therefore, avrdude has triggered both DTR and RTS at the same time to reset Arduinos for programming.
21  Using Arduino / LEDs and Multiplexing / Re: Problem with ShiftPWM and RGB LEDs on: October 14, 2013, 05:37:55 pm
Yes, this is thread drift smiley I'm just promoting mental flexibility, people love to box themselves into rules that apply to a specific subset of reality, and then generalize them onto the rest of it.
22  Using Arduino / Project Guidance / Re: Arduino based handsfree/headset for Android on: October 14, 2013, 01:37:26 am
It seems that the best way to do this would be to start with a Bluetooth earpiece. It already has most of the functions you need, you'll simply need the electronics to interface the speakers, ringer, and switch to it. Then just use the built in Bluetooth headset functions on the phone.

Your project is basically a combination of the popular Bluetooth handset hack, and Sparkfun's Port-o-Rotary phone project. You'll find most of the relevant information and electronics in those two projects.
23  Using Arduino / LEDs and Multiplexing / Re: Getting the Teensy to recongize the LED's on: October 14, 2013, 01:31:43 am
You might be able to do this by attempting to read the LED voltage using an ADC, but that may not tell you anything because LEDs are made using various chemistries. The only reliable way to do this would be to use a color sensor chip and aim it at the LED. You'll find that to be a much more expensive and complicated project.
24  Using Arduino / LEDs and Multiplexing / Re: Problem with ShiftPWM and RGB LEDs on: October 13, 2013, 08:29:55 pm
This is the best answer for small electronics systems, but don't file it away as an absolute rule because it'll cause a lot of cognitive dissonance when you see a power system that uses actual dirt as a return line.
25  Using Arduino / LEDs and Multiplexing / Re: 1 Arduino with 6 Neo_Pixel60 on: October 11, 2013, 02:13:17 pm
I'd recommend using a Teensy 3.0 instead. The OctoWS2811 library will drive 8 strips at the same time.
26  Using Arduino / Programming Questions / Re: problems with ds1307 and arduino uno on: October 10, 2013, 03:48:39 am
Perhaps this is a hardware problem? Are you sure that your DS1307 has power, the correct crystal, is running, has I2C pullup resistors, etc?
27  Community / Website and Forum / Re: Bullets not working on: October 10, 2013, 03:26:42 am
This is confirmed, annoying, and needs to be fixed. Bullet points (lists) are a great organizational tool.
28  Using Arduino / LEDs and Multiplexing / Re: Help on: October 10, 2013, 03:21:05 am
Could your question be phrased as below?

Quote
I need 3.3V at 3A, and have a 12V/3A power supply. I have some fixed-voltage 3.3V/1A linear regulators. Can I put them in parallel and get up to 3A at 3.3V from the combination?

If so, then it's highly unlikely. The first problem is that your regulators will not output exactly the same voltage; whichever one has the lowest voltage (even a small amount is enough) will attempt to supply all of the required 3A current. It will overheat and fail quickly.

The second problem is that your regulators are rated for 3.3V/1A under great conditions. First, that they don't have to dissipate too much power, and second that they are heatsinked enough to keep them near room temperature. It's unlikely that you'd even achieve 3.3V/1A from the top circuit. Your regulator will attempt to burn off (12V-3.3V) * 1A = 8.7 watts as heat. In a SOT-223, that's a lot of heat to get rid of somehow. If you look in the datasheet, you should find a table or graph that indicates what current ratings are possible at various junction temperatures. And you should also find a case dissipation rating (degrees per watt) that will help you find the difference between ambient temperature (what your heatsink can manage) and junction temperature at a given amount of dissipated watts. Then, if you're specifying a heatsink, you'll need to find out how many watts it can transfer to the air depending on various ambient temperatures.

Sound like a tough problem? It is...it's an engineering problem, not just plugging parts together and expecting them to work. You can significantly reduce the amount of risk/worry by choosing a different regulation solution:

* Find a premade regulated power supply with the desired amperage. Everything is already handled for you.

* Change the power supply to 3.3V + regulator overhead and not much else, and use a linear regulator that can supply at least 3.3V. This will greatly reduce the amount of heat dissipated from the regulator.

* Instead of linear regulators, choose a switching buck regulator design. This will have much greater efficiency, so not only is heat not a big problem, but you also aren't uselessly wasting twice the power your circuit actually needs. There are simple switching regulator designs like the LM2576 that don't require many external parts.

* Find a premade switching step-down regulator board or DC-DC converter that can supply the voltage and current you need.
29  Using Arduino / LEDs and Multiplexing / Re: Problem with ShiftPWM and RGB LEDs on: October 10, 2013, 02:46:17 am
How are you connecting the bench power supply to your circuit? Specifically...what exact pins on which parts of the circuit and Arduino are you connecting to the bench supply?
30  Using Arduino / Project Guidance / Re: USB extender on: April 24, 2013, 01:27:45 am
No. Just buy your extremely cheap and long distance USB extender: http://www.monoprice.com/products/subdepartment.asp?c_id=102&cp_id=10303&cs_id=1030312

They have HDMI ones too http://www.monoprice.com/products/subdepartment.asp?c_id=109&cp_id=10110&cs_id=1011012
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