Re: [LAU] Raspberry Pi and real-time, low-latency audio

2013/4/17 Jeremy Jongepier <jeremy@email-addr-hidden>:
> On 04/17/2013 09:49 AM, Carlos sanchiavedraz wrote:
>>
>> 2013/4/15 Jeremy Jongepier <jeremy@email-addr-hidden>:
>>>
>>> On 04/15/2013 10:39 AM, Carlos sanchiavedraz wrote:
>>>>
>>>>
>>>> Just a USB cable from RPi to an A/C to USB adapter, and UA25EX
>>>> connected direct to the USB on RPi.
>>>
>>>
>>>
>>> Check the current of the adapter, if it's somewhere around 1A you might
>>> need
>>> a more powerful adapter as the RPi already draws 700mA IIRC.
>>
>>
>> The adapter is the same as that ones to charge mobile phones, just an
>> adapter from USB to a switch. I thought it would be enough to plug the
>> UA to the RPi and not having to plug it to an USB powered hub, because
>> then it may occur problems with other devices plugged in it, and this
>> would probably increase problems with audio latency and such.
>>
>
> I haven't had any problems with audio latency and using a powered hub.
>
>

Good to know. I've had some problems before testing some other touch
device with USB, but maybe it had to do with the hub was not powered.

>>>
>>>
>>>> IIRC, when configuring using raspi-config, the Modest preset for
>>>> overclocking just increases the CPU freq from 700MHz to 800MHz. I
>>>> didn't want to risk my SD because I red that issue you mention, but it
>>>> seems that anyway I've left without my SD.
>>>>
>>>
>>> What kind of SD are you using? I've used different SD cards with
>>> different
>>> results. I'm now using a cheap OEM class 10 SD card that does get
>>> corrupted
>>> quickly but performance is better than other SD cards I've used. Whenever
>>> I
>>> change something I make a backup now.
>>
>>
>> I'm using a SanDisk 2GB microSD on a SD adapter for the RPi slot. I
>> never had any problem until now.
>>
>
> And that while SanDisk SD's are being recommended for use with the RPi. What
> core_freq are you using?

I chose the Modest preset, so it should be just 800MHz and with no
other modification on other freqs.

>
>
>> Do you still can use yours once it is corrupted? I plug it, you can
>> see the two partitions mounted for a moment but then it unmount
>> itself. I made a backup copy with dd once I configured some
>> parameters. I've and tried several times to transfer it to the SD with
>> dd again but at about 840MB transfered it stops with a corruption
>> error; I only can modify the scripts and config on the first partition
>> (boot partition) when it stays mounted for some time.
>
>
> First thing I do when a SD becomes corrupted is wipe all partitions and then
> restore an image with dd.

I tried it, but when I try to wipe partitions with gparted or any
other it unmount itself or say that it's not possible.

> If you run into corruption errors the SD might be
> defective?

At least not until now, never had a problem. I wonder if the reboot
cause a physical damage on the SD, but in a reboot it shouldn't happen
a peak of voltage to cause that.

>
>
>>
>> This could allow me to maybe boot a system in a USB stick, but then I
>> waste one USB slot, and I'm afraid that if I buy another SD card it
>> could be corrupted again and then it would be wasted money.
>
>
> You can boot from an USB stick connected to a hub. I've tested this when
> trying to run a RT kernel on the RPi. But either my USB stick or the RPi
> itself has issues with the throughput because I had the idea the RPi was a
> lot less responsive and audio was completely distorted.
>

In worst case, I could plug a USB stick on one slot and in the other
the USB hub with the UA and mouse/keyboard/midi-usb..., but I would
like to control what happen with SDs cards and when they get
unusable/broken because of some corruption.

>
> Jeremy
>
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-- 
Carlos sanchiavedraz
* Musix GNU+Linux
  http://www.musix.es
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