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61  Using Arduino / Project Guidance / Re: Can I use Arduino MEGA Serial1 TX as output pin while receiving on Serial1 RX? on: April 02, 2014, 10:18:41 am
Resetting the bit seems to work. After reading the atmel document, I felt a bit more confident with this method. Any confirmation this IS the correct method is still very welcome.
62  Using Arduino / Project Guidance / Re: Arduino with processing (which card ?) on: April 02, 2014, 09:59:39 am
In your pictures, your LED was blinking, so what issues do you still have? I'm willing to help. But point to your issue, like "This part should do X but it is doing Y or doing nothing".
63  Using Arduino / Project Guidance / Can I use Arduino MEGA Serial1 TX as output pin while receiving on Serial1 RX? on: April 02, 2014, 02:23:25 am
I am trying to retrofit a project with a enable pin and at the moment the least difficult way is to use pin 18 (serial1 TX) as an output pin to enable/disable a sensor output. I am using Serial1 RX to receive the sensor output so I can't just entirely remove the serial function of Serial1.

I tried to set pin 18 as output and set it to LOW. It didn't work. It must be driven by something else when it's used as TTL serial.

Then I realized that I should dig into the library code. What I found there, combined with doc2549 is that I can reset the register bit that enables the TX. This way I can use the pin again as gpio.

cbi(UCSR1B,TXEN1);

Is the above the correct way to do this?

BTW, is there any difference in value of TXEN1 and TXEN2, etc? Are they just trying to make things more general so in other MCU if the different TX enable pins are NOT the same bit location, they still work?

Thanks for reading!
64  Using Arduino / Project Guidance / Re: Arduino+XBee how to monitor the power supply on: March 31, 2014, 07:16:50 pm
OK, here is a diagram:

http://liudr.wordpress.com/?attachment_id=1809

You can sense battery voltage up to 15V.
65  Using Arduino / Project Guidance / Re: Arduino+XBee how to monitor the power supply on: March 31, 2014, 09:34:37 am
I usually just use a voltage divider to monitor car battery voltage, dropping them from 15V to 5V range. What type of battery do you use? To save power, you may need a switching regulator and study some power schemes on Xbee maybe?
66  Using Arduino / Project Guidance / Re: How to make a waveform generator with frequency of 20hz-20Mhz on: March 31, 2014, 09:31:57 am
0-40Mhz, Sine wave generator for $25 using the AD9850 which is a Direct Digital Synthesis sine wave generator able to control by Arduino Uno.

Thanks BillHo. I'm sure I can use this for some projects or teaching apparatus. Can't believe how easy and cheap.
67  Using Arduino / Project Guidance / Re: Vehicle with proximity detection. on: March 29, 2014, 01:18:12 am
If both theta and delta are integers and you may lose a lot of accuracy when you do the division (THETA-reading)/DELTA

Instead, do this
(THETA-reading)/(float)DELTA

Since you are assigning the result to a float already. This prevents unnecessary loss of accuracy. You should try this.
68  Development / Other Hardware Development / Re: SD card voltage level converter suggestions? on: March 29, 2014, 01:11:40 am
OK, the 74HC4050 has 6 outputs, seems overkill. I just need 3 pins. Strangely, when I googled "quad high to low level shifter", I only got pages and pages of quad low to high. I found one quad high-to-low or low-to-high, but it is just open drain and needs additional pull-up resistor:

http://www.futureelectronics.com/en/technologies/semiconductors/logic/gates/quad-gate/Pages/4848529-74HC03N,652.aspx?IM=0

Does anyone know a quad high to low level shifter that I can use?

CR, if you're reading this, do you use an EAGLE library part? I found a part "4050" and it seems to have SO16 package. But it's weird. I have to add 6 parts (logic symbol of follower) instead of like one part with 6 followers. Not sure what the logic behind this.
69  Using Arduino / Project Guidance / Re: I need some help with my project on: March 28, 2014, 01:03:17 pm
My death ray also comes with 4 wires. Please post where you purchased your load cell. You didn't provide anything useful, do better next time.
70  Using Arduino / Installation & Troubleshooting / Re: WARNING: PL2303 USB TTL chip has NO driver for win 8 DON'T buy! on: March 27, 2014, 07:58:05 pm
I haven't tried but I have used that way to install some old drivers. I don't think it is a hardware limitation, it might be something like chineses cloned that chip too much that prolific stopped supporting these old versions or something like that.

That was in my thoughts too. Make it obsolete. If you have the driver, can you tell me the file name. I just couldn't find where the install program unzipped the driver so I can't specify where to find driver smiley-sad
71  Using Arduino / Project Guidance / Re: Vehicle with proximity detection. on: March 27, 2014, 07:53:15 pm
The real problem doesn't lie in my code,
...
THETA and DELTA are ints.

I am not sure if I can agree with you on where your problem lies. At least you gave some answers to my question. So what are the values of these two integers and what is the range of values that proxL gets, from nothing in sight to object very close?

Not posting the complete code is frowned upon. You need help. The least you should do is to provide all you can on a post. Leave the worry of wasted space and long reading to the rest of us.
72  Using Arduino / Installation & Troubleshooting / Re: WARNING: PL2303 USB TTL chip has NO driver for win 8 DON'T buy! on: March 27, 2014, 05:40:00 pm
I can't even find where the pl2303 driver install program unzipped the drivers. A PL2303 driver IS installed after I plugged in the Nano but it shows error messages. The manufacturer specifically says PL2303 HXA is obsolete and has no win8 driver. Have you tried it yourself?
73  Development / Other Hardware Development / Re: SD card voltage level converter suggestions? on: March 27, 2014, 01:18:25 pm
Thank you CR! From the first paragraph I was assured that HC4050 is designed to do the job (high-voltage logic to low, and input can take 15V when supply voltage is low). I may have to make an EAGLE part. I'll check sparkfun library. They have some errors with digikey part number in their library.

So I was wondering, is it possible to save a pin by tying the CS to gnd? I'm using ATMEGA328P-AU, actually just a nano cause they are so darn cheap. How can I resist a complete package with TTL USB at $7? The downside is the one I got has PL2303 chip that the manufacturer has stopped supporting, so no win 8 drivers. I'll have to hunt down some cheap ones with FTDI chip instead.
74  Using Arduino / Project Guidance / Re: Hi new to this wonderful new World of Arduino. on: March 27, 2014, 11:40:45 am
You can start with one arduino and one servo, no buttons, and try driving the servo and reading a pot value. Then if successful, try to determine the pot value and do the variable delay. I recommend wireless solution. It saves you from having to deal with a long cable and all the problems it brings to the table. Easiest wireless is RF modules. You use one arduino to Serial.print with the RF module on the serial port, then use the other arduino to Serial.read.
75  Using Arduino / Project Guidance / Re: Vehicle with proximity detection. on: March 27, 2014, 11:29:00 am
What are the data types of theta_prox_L and delta_prox_L?
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