Significant FM radio interference

[splite]

@John, I tried several power supply. One based on a LM338K a 5 A adjustable voltage regulators witch I set on 5V, the other one, the Ipod power supply was tested with board only, so I think it can handle it!

I tried to have a look at UART0 to debug the startup but I can't see anything wrong, BOOTP was one time looping...

I can't understand why the 5V/5A power supply could not power the board correctly...The green light light a few second then stop, even the Ethernet port stopped.

What could it means ?

[jmyreen]

There are limits to how much power a USB device can draw from the bus. A USB device playing by the rules (like the Olimex boards) must refuse to break the limit no matter how powerful the power supply is. Because the board needs more power than it is allowed to use, the AXP209 circuit shuts down the board.

For more details, see this post:

https://www.olimex.com/forum/index.php?topic=4058.msg17333#msg17333

(For the LIME2, but it applies to the MICRO too.)

[splite]

@jmyreen thank for the explanations.

I understood the AXP209 can't give much power through USB_OTG, you meant the AXP209 is also working when we use USB_OTG as an imput for power supply ?

I powered the card with no peripherals, screen, only one micro-sd card and it's still not working.
The doc says :

Note that when powering the board from the USB_OTG, the power provided might be insufficient
to also power a bigger LCD connected to the LCD_con. However, this power option is capable of
driving the board when using external display connected to the HDMI connector.

Just for reminder, LIPO_BAT and 6v-16v barrel are working fine, but the in board power supply is noisy, that's why i'm looking for an other way of powering the board.

[jmyreen]

I understood the AXP209 can't give much power through USB_OTG, you meant the AXP209 is also working when we use USB_OTG as an imput for power supply ?

Yes, the AXP209 has three separate power source inputs: VBUS (from USB OTG), ACIN (external "A/C") and BAT (battery). It automatically chooses where it draws power from, depending on what's available to it. It can even mix USB and battery power, drawing as much as it is allowed from USB and the rest from the battery.

The APX209 does a lot more, too: is intended to be a complete solution for a battery powered device like, for instance, a tablet. The circuit also contains several voltage regulators producing the voltages the CPU and DRAM need, it functions as a battery charger, and it protects against over/under voltages.

I powered the card with no peripherals, screen, only one micro-sd card and it's still not working.

Well, I suppose it should work off USB power. I don't know why it's not.

On the other hand, looking at the schematic, I also don't understand where +5V for the peripherals is coming from when the board is only powered from USB OTG. Maybe I missed something...

[splite]

Thank you for the explanations about the AXP209. I understand a bit more how this chip works.

I'm thinking I damaged something but I don't understand what and where, every single chip looks fine on the board...

I planned to power all the peripherals (mostly on usb) with the USB hub.

I have been doing a little test:
- Powering through USB_OTG nothing much is happening (not enough power ??)
- Powering through USB_OTG plus serial debug plugged on UART0, I can see the board starting up, looking for an DHCP server with BOOTP, taking an IP address, then try to load a register then stop and start again...Don't know why. But what I could observer, USB_OTG + serial debug is going farther than USB_OTG only.

Does the USB_OTG needs more than 5V to power the card ?

[jmyreen]

Does the USB_OTG needs more than 5V to power the card ?

No, the USB OTG is designed to to use standard USB bus power, which is +5V.

What I really wonder is: is anybody actually using the OTG port to power the board? There seem to be serious drawbacks to using only this way to power the board. Everything on the board that needs +5V gets it either from U14, a step-down regulator that is connected to the power jack, or U16, a step-up regulator that is connected to the LiPo battery. If the board does not get power from either of these, +5V is not available. Yes, +5V comes in on the OTG port, but it is only fed to the AXP209, and the AXP209 does not output +5V.

What this means is that the board's SATA power port does not provide +5V, nor do the GPIO and LCD extension connectors. The VGA HSYNC and VSYNC signals are pulled up to +5V, which is not there. The same applies to the HSCL and HSDA signals on the HDMI connector. The USB host ports do not work.

When you also take into account the current limit on the OTG port discussed earlier, I wouldn't recommend using the OTG port to power the board. Of course, this is only how I see it, based on my reading of the circuit diagram. I would be glad to have somebody from Olimex prove me wrong.

Edit: Never mind, I see it now. U16 works as a step-up regulator providing +5V from the AXP209 output. (And U14 is not a regulator at all. What was I thinking...)

[splite]

@jmyreen thank a lot for all this explanation. True ! It would be really nice to have some info from olimex as well!

So what I can understand so far, is either the USB_OTG or LIPO_BAT are definitely not the best way to power the board.

I wonder how can I manage then to reduce the radio interference while powering the board with 12V.
I would love to have some info from @woodward who started this topic !

Still looking for a better solution...

[JohnS]

For testing why not put a decent 5V power supply into the OTG.  You want a good supply, not a cheap nasty one as otherwise you're wasting your time.  A USB hub is not a good choice because you are wanting deliberately to take far too much power from a USB.

This still may not do what you want - reading the schematic and datasheets is the way to go.  These boards are for developers!  They expect to and need to read such things   I know it's hard work but there it is.

I do hope you are SURE about grounding, shielding, where the noise is going / getting in as you're going to have yet more grief if you're wrong.

John

[robert.w]

Hello

i just test using spectrum analyzer and i see also noise.
(my setup isn't proff - antenna it is a few cm wire near to power supply in olinuxino micro)

see video:
https://www.dropbox.com/s/a8wy76natvobskl/20150810_141357.mp4?dl=0

i must do some more test to confirm this.

Best Regards
Robert

PCB rev is F

Freq on spectrum analyzer is 85 - 115 MHz
You cen see signals from FM local radio stations when olinuxino is OFF


UPDATE 11.08.2015

video:

https://www.dropbox.com/s/lp1aih7yvp1d2k7/20150811_122602%5B1%5D.mp4?dl=0

olinuxino is powered from 5 V ext power supply via 5V_PWR connector (near the serial ata)
I solder 5V_E pad but when i add voltage to  5V_PWR connector i obserwe that voltage pulisng from 5V to 0V and micro can't start (red diode also pulsing)

after this i desolder L19 ad R80 and now it working.

I can't see now any noise on spectrum analyzer after first tests.

work in progress

UPDATE 17.08.2015

I just test rev G of the board and is much better. (without board modification from +12V)