Pages: [1]   Go Down
Author Topic: Arduino freezes if blinkm is not connected to pwr  (Read 383 times)
0 Members and 1 Guest are viewing this topic.
0
Offline Offline
Newbie
*
Karma: 0
Posts: 23
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hello,

I just found out some strange behaviour between arduino and BlinkM.
In my setup I use external psu to power the BlinkM MaxM.
This power will be triggered via arduino.

The strange thing is... When I start up the arduino, it freezes if a BlinkM is connected via the C&D wire, but doesn't have power.
If I disconnect the Clock&Data wire, the blinkm continues running the program like nothing happend (until I cut the power to the blinkm, then arduino freezes again).

I have to remove the Clock AND data wire, removing only one doesn't change a thing.

It took me a while to get here and hope there is some logical explanation for this. I've send an email to BlinkM hopefully they
can explain what happens.

See my other thread about my project and code:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1245352480
« Last Edit: June 23, 2009, 04:59:25 pm by boomy » Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 23
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Just mailing with ThingM and I came up with some other findings:

I've read the following: http://datasheet.digchip.com/000/000-1-PCF8571.pdf
Both data and clock remain high when the bus is not busy.

This is true. When I don't connect a blinkm and start the l2c bus command BlinkM_stopScript(blinkm_addr); I measure +4,5v

But if I do this with a blinkm connected without power to the blinkm the bus is 0v and will be "bussy".

I think this happens because the blinkm shortens the C & D if it's not powered. I measure 1.4 Mohm between C&D without power to the blinkm. This changes to infinity when the blinkm gets powered.

As this is my measure result, I'm trying to find this information because I also would like to read it in the factsheets of the protocol.
Logged

SF Bay Area
Offline Offline
Edison Member
*
Karma: 11
Posts: 1244
Arduino Ninja
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

That's correct, the BlinkM is based on an ATTiny and the internal clamping diodes on the pins will pull the signal low when the device is not powered. Not a good idea to do this because those diodes aren't designed to handle much current.
Logged

Unique RGB LED Modules and Arduino shields: http://www.macetech.com/store

Pages: [1]   Go Up
Jump to: