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1  Using Arduino / Motors, Mechanics, and Power / Re: Power Protection on: September 05, 2014, 06:21:28 pm
If you're worried about spikes put 0.1 uF caps on your arduino 5V lines and use a large Electrolytic (1000 uF or greater across the 5V line. ) That will suppress any spikes and keep the logic voltage stable.
Wow: 1000uF is a big cap!  Did you mean on the 4.5V battery supply?

I'm mostly concerned about some kind of motor-generated transient frying the boost regulator circuit.
2  Using Arduino / Motors, Mechanics, and Power / Power Protection on: September 05, 2014, 04:03:34 pm
I'm building a robot wall-racer car.

I'm powering the motors with a 4.5v battery pack and at present I have the logic circuit powered by a separate voltage regulator and 9v battery.  The logic draws about 50ma.  I don't really know the draw of the motors.  I'm using a pololu MD08A motor driver

I have a pololu 5V boost regulator which would easily supply the 5V for the logic from the car's battery pack but I'm nervous about spikes.  Is the circuit below safe?  Can I improve it by putting a diode before the motor driver?  I don't want to do this if I don't have to because it will waste motor voltage.
3  Using Arduino / General Electronics / 5V External Supply on: August 31, 2014, 02:27:08 pm
My circuit does not have a built-in power supply, it's normally fed direct from computer USB or a wall-wart, but now I want to be able to run it from an external battery.  I  need something like 60-100ma

I bought a USB portable power bank  but I find that it drops its output briefly to 3.5V every 10 or 11 seconds.  Needless to say, that's not ok!

This sounds like the problem described by Paul on dorkbotPDX if the circuit doesn't draw enough power.  He solves it with a circuit that keeps the USB supply alive with a dummy load that kicks in  briefly every 1.4 seconds.  I would prefer to avoid the clutter if I could.

I could try another brand or I could roll my own with a 9V battery and a 7805.  I wondered if the mintyboost type of supply would have the same problem.
4  Using Arduino / Networking, Protocols, and Devices / FT245 Automatic Reset on: June 19, 2014, 06:33:53 am
I'm working on PC communications for a micro(an RCA 1802)  that doesn't have its own uart.  My current solution uses an FTDI cable and a big AVR as a bridge but it takes up a lot of room and is generally ugly.  The setup is arduino-like in that avrdude can send code to the 1802 thru the avr.  The avr resets the 1802 when it is reset by avrdude opening the port.

I was thinking about an FT245RL.  I could interface it easily enough directly to the 1802, then code in the 1802 ROM could do the bootloader function but I don't see a way to do an automatic reset when the "port" is opened by the PC.  There is a pin called PWREN#  which sounds like tells you when the USB is plugged in but not when a port is opened.
PWREN# goes low after the device is configured by USB, then high during USB suspend.
Can be used to control power to external logic P-Channel logic level MOSFET
switch. Enable the interface pull-down option when using the PWREN# pin in this
way. Should be pulled to VCCIO with 10kΩ resistor.

Anybody have any direct experience with behaviour of PWREN or any other ideas?

Bill Rowe
Olduino - An Arduino For the First of Us
5  Community / Bar Sport / Re: RBBB's are more expensive now, NOOOOOOOOOOO on: April 25, 2014, 05:42:49 pm
I really like the RBBB. I use mine all the time and I've used the schematic a bunch as the basis for my own work.
6  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 10, 2014, 11:31:06 am
Thanks again for the help, software serial works fine at 57600 - now on to the spi bridge and memory challenges.  For one thing I need a 256 byte input buffer!
7  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 12:37:35 pm
ok, thanks again.  I got the 2313 working and i've now got the '84 working, I understand software serial works there so I'll be using that.

8  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 10:45:23 am
This is the entry in programmers.txt  I used when I used the pololu programmer

Code: USB AVR Programmer

and in boards.txt uncomment pololu programmer

# The following DO work (pick one)...
# attiny85at16e.upload.protocol=avrispv2

Thank you VERY much.
9  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 10:22:22 am
And I can get it to load by manually issuing the same command the ide was using changing its -c parameter from -cstk500v1 to -cavrispv2 based on reading the pololu programmer web site.

-CH:\apps\arduino-1.05\arduino-1.0.5\hardware/tools/avr/etc/avrdude.conf -pattin
y2313 -cavrispv2 -P\\.\COM4 -Uflash:w:C:\Users\Bill\AppData\Local\Temp\build4423

That led me to try changing the boards.txt to "attiny2313at8.upload.using=pololu" but nope, that wants a usb connection.

I wonder if "programmers.txt" is still a thing.
10  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 10:13:45 am
You can find the pin asignment in pins_arduino.c

This is for ATtiny2313:

//                   +-\/-+
//      (D 17) PA2  1|    |29  VCC
// RX   (D  0) PD0  2|    |19  PB7 (D  16)
// TX   (D  1) PD1  3|    |18  PB6 (D  15)
//      (D  2) PA1  4|    |17  PB5 (D  14)
//      (D  3) PA0  5|    |16  PB4 (D  13)*
// INT0 (D  4) PD2  6|    |15  PB3 (D  12)*
// INT1 (D  5) PD3  7|    |14  PB2 (D  11)*
//      (D  6) PD4  8|    |13  PB1 (D  10)
//     *(D  7) PD5  9|    |12  PB0 (D  9)
//             GND 10|    |11  PD6 (D  8)
//                   +----+
// * indicates PWM port
Brilliant - thanks.  I foolishly looked in pins.arduino.h thinking they'd be in a header file.
11  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 09:59:06 am
well here's a bunch of no fun - it compiles but it won't load.  I know it works in studio with avrisp on com4 so I've selected "attiny2313at8.upload.protocol=avrispv2"  and port com 4.  I get the first set of gibberish.  Tried using "upload using programmer" with programmer set to avrisp and i get the second set of gibberish - which looks a bit more informative at least.
12  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 09:54:27 am
The Serial class in tiny cores is ouput only, so you'll need to use another serial library to receive.

thanks: is this true for the 2313 as well?  It might just be easier for me to use avr studio.  I have a good sized arduino program that I want to port though so I'd much rather stick with the IDE.

also: how do i map which pin is where for the various processors?
13  Using Arduino / Microcontrollers / Re: Where to start: arduino-tiny on: January 09, 2014, 09:35:42 am
Ok, I've switched to a 2313 and I have my breadboard setup working to do a blink under avr studio 4.

next step: the IDE with @ 8 MHz

14  Using Arduino / Microcontrollers / Where to start: arduino-tiny on: January 09, 2014, 07:58:21 am
I have another project where I would like to include an attiny - right now it's an attiny84.  It would be an spi slave on one side connected to PC-serial on the other side - needs to be bidirectional.  

-downloaded the latest 1.0-type library from here 0018 from google code

-put it in the sketch folder and copied the " @ 8 MHz  (internal oscillator; BOD disabled)" board type to a new boards.txt

-cobble up a breadboard connection for the '84 and start playing with code

Is there a worked example or tutorial somewhere?

I bet a lot of people would appreciate it if there was a sticky at the head of this forum that would point to the latest stable tiny cores and tutorials/examples of use.

Edit: And the sticky should tell you how to track which pin is which and what is supported e.g. serial in/out
15  Using Arduino / Networking, Protocols, and Devices / Re: Could an AVR SPI slave bit-bang its own clock with another pin? on: January 01, 2014, 01:28:14 pm
So you want it to generate the burst of 8 clocks once it sees it's chip select line go low?
I suppose you could turn on a PWM output and then back off again with some assembly level code to do it quick; if your SPI is at 4MHz tho you may not have time.
Yes, it wouldn't be checking its chip select line, it would be a different pin because it might not be the active slave in the conversation but that is the idea.  In my current implementation another attiny is watching the trigger pin and generating the 8 clocks.

As I think about it though, I have to turn interrupts off in the clock-generator attiny not to miss trigger events  and that would make it tough to use the uart and spi hardware.

so... overall dumb idea.  Thanks though.
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