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Topic: Differences between ARM3 and Microcontrollers (Read 3 times) previous topic - next topic

funkyguy4000

Okay, I'm going AVR.  That is probably the best article I've ever read!
One question, I was hoping that I could have the leds kinda dimly fade in and out when the whole thing is in power save mode but then be controllable by a TLC5940 when it isn't in power save, but rather being used.  Is there a way I could send the 5940 fade data and just have it loop while the ATmega is in power save mode? (I guess what I'm asking is once the data has been shifted into the 5940's register, could I just supply it with power, put the ATmega to sleep, and have the fades still loop?)
Accelerate to 88 miles per hour.

Grumpy_Mike

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(I guess what I'm asking is once the data has been shifted into the 5940's register, could I just supply it with power, put the ATmega to sleep, and have the fades still loop?)

No, because the TLC5940 needs a external clock from the processor. If it goes to sleep the clock stops.

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You aren't helping one bit.  Stop post farming or help.

Ah, not come across that term before, you are certainly right.

funkyguy4000

#17
Dec 14, 2012, 11:07 pm Last Edit: Dec 14, 2012, 11:09 pm by funkyguy4000 Reason: 1
I just made the term up, I used to play a lot of video games and that was the general term for actions such as that. (action) - farming

Anyway, I know this topic is called anything related to the TLC5940 or lighting, but is there something I could use that would be able to fade all 3 leds of 4 RGB leds that can do what I need?  I've done quite a lot of looking around in my spare time, and although I've never looked specifically  for an IC that doesn't need the clock signal, i've never seen one.
Accelerate to 88 miles per hour.

fungus


I won't be doing visual processing at all.  Its just a few leds and sensing capabilities.  The thing that gets me still is the power consumption, like the guy said earlier, I could use interrupts to solve that, although I will then run into another problem with clock speed.  This will be powered by a LiPo battery (3.7v) and to get the ATmega32u4 or 328p up to 16MHz clock speed, I need the full 5v.  I've never done a buck-boost application or basic transistor stuff.  Is there a simple solution that can solve that or would an 8MHz clock speed be okay for just sensing with gyro, megneto, and accel sensors?


Does anything else need 5V? Boosting is easy - just buy a 5V boost board.

OTOH you're trying to use as little power as possible so running at 8mHz is best if nothing else needs 5V. 8mHz is plenty fast enough for reading a few sensors.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

funkyguy4000

Actually, nothing will be running on 5v.
The whole thing will be powered by a 3.7v LiPo.

I remember I once tried to burn a bootloader for an ATmega328p on a breadboard for 3.3v use at 8MHz and I couldn't get the darn thing to work.  Since then, I haven't figured it out. 
Accelerate to 88 miles per hour.

retrolefty


Actually, nothing will be running on 5v.
The whole thing will be powered by a 3.7v LiPo.

I remember I once tried to burn a bootloader for an ATmega328p on a breadboard for 3.3v use at 8MHz and I couldn't get the darn thing to work.  Since then, I haven't figured it out.  


3.7 vdc is just a nominal voltage value stated for a Lipo cell. Note that a Lipo cell's terminal voltage varies with it's state of charge from 4.2vdc full charged to 3.0 to fully discharged and any further discharging can damage the cell if unprotected. Be sure whatever you are powering is rated for up to +4.2 vdc or higher.

Lefty

funkyguy4000

Thats a good point.  I could still boost things up if needed, but nothing needs to be at 5v.
I understand what you mean by unprotected but I don't quite get how I would become protected.  What components would I need to make sure I didn't discharge too much?
Accelerate to 88 miles per hour.

retrolefty


Thats a good point.  I could still boost things up if needed, but nothing needs to be at 5v.
I understand what you mean by unprotected but I don't quite get how I would become protected.  What components would I need to make sure I didn't discharge too much?



Some Lipo cells (more expensive for sure) have small embedded electronic module to protect the cell from over-discharge and overcharging. Most Lipo chargers also handle the over charging problem, but over discharging (if not built into the cell, check it's datasheet to see if it states having such protection) is up to the user by either continuously monitoring the cell voltage and switching off the load when the lower voltage limit is reached.

Lefty

funkyguy4000

Hmm, well the cells i'm using are actually cell phone batteries.
I once opened one up (the connector, not the actual battery) because I destroyed its terminals by accident and I there was a rectangular circuit board it it, which I happen to still have.
It has a B+ and B- soldering points, a TSSOP package with the code 8205A on it, a chip that looks like an sot, maybe SOT23-6 (it has 6 pins) with the code DW012 or DW01E, and then 2 resistors and a capacitor, and then 4 soldering joints for the pieces of metal that made the connecting points to the cell phone.

EDIT: oh and on the backside, there is a silk screen, describing the 4 soldering joints. P- P- HT P+
Accelerate to 88 miles per hour.

Grumpy_Mike

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although I've never looked specifically  for an IC that doesn't need the clock signal, i've never seen one.

TLC 5945 or TLC 5947 ( I think )

funkyguy4000

Okay, I'll look in to those!
Thanks a bunch!
Accelerate to 88 miles per hour.

Grumpy_Mike

The PCA9685 is an I2C interface, and that will keep going in the absence of any input signal from the arduino as well.

funkyguy4000

Hmm, I like how there is a specific dedicated library for it although the TLC5947 is a 24 channel, which is exactly how many I need.  And seeing as How I have no issues with surface mount soldering of any kind, I was thinking about that one.  I'm left wondering if it could be controlled by the TLC 5940 library.
Accelerate to 88 miles per hour.

Grumpy_Mike

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I'm left wondering if it could be controlled by the TLC 5940 library.

I would not think so because that library provides a clock to synchronise the data transfer.

funkyguy4000

But isn't that okay?
The functional diagram on the TLC5947 page shows it has a connection for serial clock

The tlc5947 datasheet says its data transfer rate is 30 MHz
The tlc5940 datasheet says its data transfer rate is also 30 MHz

Hm, wait. the 5940 sclk pulse is 16 ns long where as the 5947 is 12ns long.  Well that would be an edit I could do in the 5940 library to make it work for the 5947, right?
Accelerate to 88 miles per hour.

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