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Powering SEQ with USB Hub problem

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Normally I power my SEQ with a 5V, 2,5A power supply connected to J2. I also have J17 closed to provide power to USB gear connected to the USB socket in host mode.

I would like to use it with my computer, and power it over USB, of course without the PSU connected to J2.

I have a STM32F4 core with 2 x MIDI I/O, 2 x IICx4, BLM 16x4, TPD and AOUT_NG.

I have not measured how much current this all draws.

When I connect it to my computer with a Belkin  USB 2.0 Hub with external PSU, the SEQ starts up, and runs but the LCD's are very dim, I can only see very little text, and only in the dark.

I assume that the USB Hub does not provide enough current, and that the LCD's are suffering from that.

I can't find any specific info about current per port for this Belkin Hub, but I assume it has some sort of limiter set to the 500mA standard. It has 7 ports, and a 2,5A PSU.

Can anybody suggest a solution for this? Do you know of a specific USB Hub with external PSU and ports without current limiting?

Cheers, Hal


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I have now tried with a Y cable straight to the computer, but it didn't help.

Also tried with a new USB 3.0 Hub, which in theory should provide 900mA per port, and with a new USB 3.0 cable and the USB 3.0 Y cable from 2 ports which then should provide 1,8A, but still not lighting up properly :(

I guess I need to power it with my 5V PSU, and connect a switch to J17.

Or maybe a USB cable without the power wires? Don't know if that exists or will work even ??????

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It should be possible to transport 2 amps through a micro USB connector, if the cables and connectors are good (many chargers deliver this for "medium quick" charging phones). Can you measure current draw with the setup when the LCDs are dimly lit?

Second step: can you try to power the setup with a high quality USB charger or powerbank and a high quality cable? I have an Anker 10000mAh powerbank, that came with a high quality micro usb cable - this combination powers my "flatsequencer" (2x OLEDs, full MBSEQ CS + TPD) without troubles - the same cannot be said by some of the USB hubs here. On paper, they should be able to do it, too, but they fail rather spectacularly ;-), i don't know why that is. A lot really also depends also on the cable used.

Finally, it may also be a problem on the core connector side - I managed to break off two connectors already, they are very flimsy on the discovery boards and the traces are hair-thin. If that is the case, you could try to directly power via J2 and rejumpering J17, it would be possible to split a usb cable and put power to J2 while soldering the data pins to the protection resistors on the discovery board. I did this lately, because i broke another connector, now i have a USB cable directly soldered to the core ;-).

Many greets and good luck!

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I have now tried with my SONY phone charger that provides 1,5 A, and still no change.

The sequencer is running fine, and all the LEDs are bright, it's only the LCDs

I wonder if is has to do with the way I power them. I have modified the Core like you Altitude. I use the Kyocera LCDs



I can't see how it would be different. It's the same 5V on the same rail.???

I have read about a Data only USB cable, some people use for their audio interfaces.

I might try it. I would like to avoid having a switch on J17 that I could forget to turn off, and fry my computer. 



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Are you using the Micro-USB or the Mini-USB port for powering your SEQ?

The 5V of the Micro-USB port is directly connected to PA9 which is then connected via the jumper J17 to the board. Exactly the same as you power your setup via J2. Should be no difference.

The 5V of the Mini-USB port goes through a BAT60J diode to the board. It has a voltage drop of 0.28V... 0.58V depending on the current flowing through it. 


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On 17.9.2017 at 2:00 AM, Altitude said:

I think that there is something else pulling it down, I run mine on USB power all the time when I'm flashing it, check resistance between +5 and gnd and +3.3 and ground

Resistance between 5V and G is 938 Ohm, and between 3V and G it's 1,9 K

On 17.9.2017 at 9:54 PM, CJ55 said:

Are you using the Micro-USB or the Mini-USB port for powering your SEQ?

I am using the Micro-USB

I think it's down to bad cables, because when I connect my 1,5A phone charger with Micro-USB directly to the Discovery board, it lights up fine.

I have an ebay panel mount female USB A socket connected to a Micro-USB cable where I have soldered a cable to Pin 4 so I can pull it to G for USB Host mode. I think this together with a cheap USB 2.0 A to A cable is the problem.


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On 19.9.2017 at 8:26 AM, latigid on said:

What's the total resistance between the +5V on the Disco board and the far end of the out USB? All of the connectors will add up. 

It's only about 0,7 Ohm,

I have taken it apart an checked the socket and cable etc, can't find anything.

Then I thought it could be a ground loop through the USB socket since it touches the alu panel, but after clearing them by adding a spacer, no difference.

I have tested with different types of cables, directly to the Disco board, and there is a difference, so it could have something to do with the quality/length of the cable.

Anyway, I have given up and made a "Data-only-USB-cable" so I can power it with my trusty 5V PSU, and connect it to my computer with that. That way I can keep my "USB Host Mode" wiring  :)


Thanks for the troubleshooting support guys :happy:


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