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1  Using Arduino / Project Guidance / Re: Trouble with Serial1 and Digital 2 (pin 2) input on Leonardo on: October 01, 2014, 06:50:29 pm
Ah, the age old problem of having two inputs that cannot find common ground.
2  Using Arduino / Microcontrollers / Re: What's this I found on eBay? on: September 30, 2014, 06:12:16 pm
My Maple-Mini-Clone finally arrived today.  

Anyone else get theirs yet?

My tracking number says "In transit"... I have 3 coming, so work out the bugs! (please)
I have been working with the PSoC 4200 ARM units, so I have about 90 days of beyond-Arduino there.  The 810 guys in another thread have their 8-pin ARM programming under Arduino... Pretty cool.

3  Using Arduino / Sensors / Re: problem with max31855 and multiple thermocouples on: September 29, 2014, 08:01:37 pm
Just as a sanity check, here is test code and schematics for dual and quad 31855 breakouts.
Good luck
4  Using Arduino / Sensors / Re: problem with max31855 and multiple thermocouples on: September 29, 2014, 07:34:38 am
Not to offend you, but your Arduino logic CS logic does recognize that CS is a /CS signal, that is it is active low.  
6 CS Active-Low Chip Select. Set CS low to enable the serial interface.
This would mean, at a minimum, that your CS pin logic must have a pull-up resistor and I'm not sure if internal AVR weak pullup is satisfactory.

Also, this is a 3.3V chip, so how are you buffering the Arduino signals?  Or, are you running an 8MHz 3.3V Arduino?
You stated:
I have also added an on-breadboard level shifter for clk channel and only ic2 works.
but gave no specific details.

You may want to search the forum for 31855 and see if others have had similar issues with connections such as pull-ups and how they have resolved the 5V to 3.3V logic conversion (there are several 'good' ways to approach this.)

5  Using Arduino / Sensors / Re: problem with max31855 and multiple thermocouples on: September 28, 2014, 09:39:25 am
Still only ic2 works.

Without further testing, IC1 would seem suspect.

As I understand,
IC2 always works, with CS1 or CS2.
IC1 nevers works, with CS2 or CS1

Can the 3rd 31855 be wired as if it were CS1?  That would prove or disprove a bad chip.

6  Using Arduino / Sensors / Re: problem with max31855 and multiple thermocouples on: September 27, 2014, 07:05:15 pm
So, if you swap in firmware CS1 and CS2, does the IC1 work on CS2?  Does IC2 work on CS1?

This is a divide-and-conquer opportunity.
7  Using Arduino / General Electronics / Re: Cheap power for LED Night Light. on: September 27, 2014, 06:18:43 pm
Is there any other alternative I should know about?

Amazon sells Wii battery packs w/ the USB cord for cheap.  These are ideal for battery powered projects:
Example under $7 free shipping:

8  Using Arduino / General Electronics / Re: 10mm Ultra Bright LED with no resistor? on: September 27, 2014, 06:07:29 pm
LED voltage drop is a function of design and color (plus age, junction damage, etc)
And the CMOS output driver in the AVR also has a 0.3-0.6 Voltage drop typically based on sink/source connection to the load.  Your (supply voltage - (LED Vd + CMOS Vd) ) / LED desired mA = the proper resistance.

If you are working with a LED that has a Vdrop too great for 3.3V, then a MOSFET transistor can be used to source the LED to a +5 or higher Vc such that you can get the correct current flow for consistent brightness.

In my designs, I often use a buck DC-DC converter to derive the 3.3 uC & sensor voltages but source the LEDs back to +5 or +12 that feed the 3.3V DC buck unit.  Use care in automotive use as the +12 volts can go upwards to 17V during lead-acid battery charging.  In these cases you may wish to consider both +3.3 and +5 voltage regulation.

9  Using Arduino / General Electronics / Re: About LCD compatibility on: September 27, 2014, 05:46:00 pm
which LCD is compatible with Arduino mega? can i use any one type of LCD ?

A bit of research is necessary... Find the display type you need, determine the controller chip (usually in the description or eBay heading), find an appropriate library for the LCD+chip set, then verify the library runs on the Mega2560 without conflicts.  Using the forum search will be helpful...
For example, if I needed color TFT, found it on eBay, identified the chip as ILI9341, then I would search this forum for the ILI9341 and start reading what others were doing.

Of course, you can buy-in to a shield from Adafruit or Spartfun that will guarantee some level of compatibility, but you may still have conflicts down the road with sensors or other peripheral devices.

10  Using Arduino / Microcontrollers / Re: Can't Use an Arduino as ISP on: September 27, 2014, 05:05:25 pm
Let me get this straight.

If I succeed at loading in a sketch to a Leonardo with a Duemilanove ISP to act like a mouse, it will overwrite the bootloader but the Leonardo will nonetheless work like a mouse. If so, at this point I will be happy to have it work. Since the bootloader does me no good, it'll be fine by me to dump it.

Now, about the Duemilanove ISP problem...

Yes, that is my understanding too based upon hiduino's input - there is obviously a full LUFA library that gets automatically linked.  As for the ArduinoISP, maybe this will shed some light:
Regretfully, I am not Linux user.

11  Using Arduino / Programming Questions / Re: Storing Code on an I2C EEPROM on: September 26, 2014, 10:14:13 pm

Just a quick thought... Assuming that I could re-write the boot loader, would you still have access to I2C components? Like an external EEPROM? And the boot loader would have to contain any libraries to access routines you would use?

Existing I2C AVR boot loader:

A little google goes a longggg way.

12  Using Arduino / Programming Questions / Re: Storing Code on an I2C EEPROM on: September 26, 2014, 09:00:18 pm

What I wanted to know is this: Can I store executable code on the EEPROM and load it into my Arduino then call it as a function?

Assume you make a switch-case statement large enough to cover all math operations & transcendals such as sin & cos.  You could read the verb from eeprom/SD, look it up in a table, and use the table pointer to switch-case.  This avoids a BASIC style interpreter but stills requires an offset either through an array search or by entering the offset value directly in the eeprom (short circuit the lookup.)  You can then read the arguments from serial, eeporom, SD, or a pheripheral device.

As an example of how this may be put together, consider this very simple application that parses the serial stream and functions as a calculator:

There really is no limit on how diverse you can build such a machine... You just need to ensure that during the sketch compile that you have linked-in all of the AVR/Arduino functions required to support your interpreter... The switch case construct ensures this, but other implementations must ensure that the compiler "knows" about external references.

13  Topics / Science and Measurement / Re: Arduino 50 Hz sine wave Analog read problem on: September 26, 2014, 07:01:39 pm
this signal is 50 Hz.
 as peak. when i give 5 v to the that pin then it gives 1023 also. what is the problem. Can you help me?
Here i attached the arduino readings and the screen shot of the oscilloscope.

You are misunderstanding what you are measuring w/ the o'scope.
You are simply measuring the power-line 50Hz inducement into the open wire connected to a probe with a 1 megaOhm typical AC/DC impedance.
W/Arduino, the AC hum inducement will be based upon the ADC characteristic DC impedance of approx 100 megaOhm.  But, Atmel indicates that a DC impedance of 10 kiloOhm is desired for accurate ADC measurements:
(23.6.1) Page 257 states: "The ADC is optimized for analog signals with an output impedance of approximately 10 kΩ or less. If such a source is used, the sampling time will be negligible. "

Then there is the whole issue that on the Arduino, you can only measure positive voltage, so the input signal must " ride" a bias voltage to allow the +/- nature of the AC to be DC offset.

So, in American lingo, you are comparing Apples to Oranges.

14  Using Arduino / Microcontrollers / Re: Smaller substitute for Arduino uno on: September 26, 2014, 06:37:05 pm
OK, so I won't feel guilty for hijacking this thread.  Anybody have an opinion as to why I see many suppliers of Pro Minis and Nanos on ebay, but very few suppliers of Micros?  It's just curiosity that makes me ask, as I have bought several Micros from a supplier that is cheaper than the few I saw on ebay.

Opinion: Inventory and profit... Ability to do midnight runs while paying off the night security guards.  I was able to purchase 20 of the Micros recently for ProMini price simply because the antistatic packaging was mismarked.  My guess is a significant quantity of the low-cost boards are coming from "dark" factories.

15  Using Arduino / Microcontrollers / Re: ATMega1284P Bootloader Assistance on: September 26, 2014, 06:24:18 pm
I have worked w/ 1284 a bit, but always have used 16MHz 20ppm crystals and 18pF load caps.  I highly recommend member Crossroads 1284 bare boards for 1284 work.  Well designed and economical.

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