Re: Re: Turtle Art sensor xo 1.75 range voltage
Testing on SKU199 and SKU204, the impedance has gone from 1k to 4k and the calibration is all wrong on 204 Possibility of damage? How are you measuring this, so that I can reproduce on units that I believe are undamaged? Are you measuring DC impedance with laptop power off, or on? With the microphone bias off or on? With the DC mode off or on? Thanks James Testing is with Turtle Art V140, ie I am letting TA do the ALSA stuff, setting up bias, gain etc The turtle code is forever print voltage To check voltage calibration for +ve voltages and measure impedance I use the existing bias (however the turtle code and ALSA have set that up) and a variable resistor on the mic input. I estimate input impedance by setting the variable resistor that results in half voltage (1.5V) as measured with a multimeter. I check voltage calibration by measuring V across the variable resistor with the multimeter. I can see a possible error in my method, SKU204 OS12 may be changing the bias conditions briefly during the measurement. This does not have any effect however on the calibration for 0V which is changed - in this case the source impedance is zero. If the kernel is running, are you measuring with the same kernel? Quite possibly not. SKU199 is running OS32 and SKU204 is running OS12 which I think has kernel version issues. I updated OS12 with olpc-update, I presume that does the kernel too. There are some differences against 1.5, in that there are two channels, on the tip and ring of the connector respectively. Please make sure you are using a stereo plug with correct manufacturing tolerances. Test for shorting between the left and right channel pins after the plug is inserted. I thought the 1.5 was stereo too? Just the XO-1 mono? I am not getting channel shorting, different results on the 2 channels. After the socket, there is a 470 ohm series resistor on each channel. After that, reverse diodes to ground and +3.3. Thanks for confirming Tony ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: Turtle Art sensor xo 1.75 range voltage
On Sat, Jun 02, 2012 at 12:36:08PM +1000, fors...@ozonline.com.au wrote: Testing on SKU199 and SKU204, the impedance has gone from 1k to 4k and the calibration is all wrong on 204 Possibility of damage? How are you measuring this, so that I can reproduce on units that I believe are undamaged? Are you measuring DC impedance with laptop power off, or on? With the microphone bias off or on? With the DC mode off or on? Thanks James Testing is with Turtle Art V140, ie I am letting TA do the ALSA stuff, setting up bias, gain etc The turtle code is forever print voltage Could you please explain how to do this? I've not used Turtle Art, so don't presume any foreknowledge. Or, could you use alsactl store in the test state, and provide the file it generates. I can then use it on alsactl restore and be sure of the same ALSA mixer configuration. To check voltage calibration for +ve voltages and measure impedance I use the existing bias (however the turtle code and ALSA have set that up) and a variable resistor on the mic input. I estimate input impedance by setting the variable resistor that results in half voltage (1.5V) as measured with a multimeter. I check voltage calibration by measuring V across the variable resistor with the multimeter. I can see a possible error in my method, SKU204 OS12 may be changing the bias conditions briefly during the measurement. This does not have any effect however on the calibration for 0V which is changed - in this case the source impedance is zero. If the kernel is running, are you measuring with the same kernel? Quite possibly not. SKU199 is running OS32 and SKU204 is running OS12 which I think has kernel version issues. I updated OS12 with olpc-update, I presume that does the kernel too. Okay, please compare with identical kernels. There has been a bit of change in the audio driver. Use uname -a to check the kernel revision. There are some differences against 1.5, in that there are two channels, on the tip and ring of the connector respectively. Please make sure you are using a stereo plug with correct manufacturing tolerances. Test for shorting between the left and right channel pins after the plug is inserted. I thought the 1.5 was stereo too? Just the XO-1 mono? My mistake. I've been working on XO-1 all week. ;-} I am not getting channel shorting, different results on the 2 channels. After the socket, there is a 470 ohm series resistor on each channel. After that, reverse diodes to ground and +3.3. Thanks for confirming I'm not sure about the wattage of the 470 ohm resistor though, I'll leave that to someone else to confirm. -- James Cameron http://quozl.linux.org.au/ ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: Re: Turtle Art sensor xo 1.75 range voltage
Thanks The turtle code is forever print voltage Could you please explain how to do this? I've not used Turtle Art, so don't presume any foreknowledge. look at the blocks submenu, the 4th item from the left in the main menu look at the 'flow operators' pallette the 5th item in the submenu, icon is circular arrows drag 'forever' onto the canvas from the extras pallette, 9th in the submenu, icon is cog drag 'print' and dock it under the RHS of forever from the sensors pallette, 7th in the submenu, icon is plug drag 'voltage' and dock it to the right of print click on the forever block to run (I have just discovered a bug in the stereo channel selection, sometimes the left channel is voltage and the right voltage1, sometimes they swap) Or, could you use alsactl store in the test state, and provide the file it generates. I can then use it on alsactl restore and be sure of the same ALSA mixer configuration. is alsactl store fails, cannot open /etc/asound/state for writing: permission denied Okay, please compare with identical kernels. There has been a bit of change in the audio driver. Use uname -a to check the kernel revision. How do I interpret the output? Tony ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: Re: Turtle Art sensor xo 1.75 range voltage
James I think I have eliminated software differences. Both laptops reflashed to OS8 (12.1.0) Turtle Blocks V141 ( a new version is just released) Phono plug with left-right-ground all shorted forever print voltage displays: 0VSKU199 -1.3V SKU204 Tony ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: Turtle Art sensor xo 1.75 range voltage
Wad, thanks, Tony On Jun 1, 2012, at 9:24 PM, fors...@ozonline.com.au wrote: We should test the calibration again. Walter, Guzman Testing with TA140 It looks like the 1.75 audio circuit was changed between the preproduction and the ramp unit 1.75's Testing on SKU199 and SKU204, the impedance has gone from 1k to 4k and the calibration is all wrong on 204 (TA calibration should be OK for the moment on preproduction SKU199) Can laptop.org please confirm that there was an audio redesign between SKU199 and SKU204? Is the SKU204 design now stable or can we expect further changes? Yes, there was a redesign which increased the resistance between the Mic voltage source and the mic jack from roughly 1K to roughly 3K for improved microphone performance.All production XO-1.75s use the SKU204 circuitry. Is the input protection the same as the 1.5: The XO-1.5 is protected by a resistor,(1/16W 470 ohm SMD0402) and a pair of diodes to ground and to +3.3V which should protect -6V to +9V continuously, and up to higher voltages for shorter periods of time. http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Specifications Yes, the protection circuitry is the same as used on 1.5. Chers, wad _ This mail has been virus scanned by Australia On Line see http://www.australiaonline.net.au/mailscanning ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
