--- In "wrsimpson.alaska" <> wrote:
>
> Hey Charliem_1216-
>
> Thanks for the information. I'm using the 2.4 kernel, so I don't know the
> overcurrent condition in the syslog.
>
> Regarding one or two ports, I see that the USB power on the TS-7260
> schematic is just wired to both of the 5V power pins on the connector, so I
> don't think I get any more power by using two connectors.
OK, I thought the MIC2026 chip was doing the current limiting for two channels.
AFAIK, there are low power devices (never draw more than 100 mA) and high power
devices (up to 500 mA). High power devices are not supposed to exceed 100 mA
draw until the host configures the device, after the host has determined that
it has 500 mA available. You should check with Ocean Optics to see whether the
microcontroller in the spectrometer obeys that restriction.
>
> I don't really have space in the design to fit a USB hub in between the
> devices. Additionally, I'm not sure I like the reliability of using an extra
> device in there. This application is part of an autonomous instrument that
> is deployed for a year at a time.
You probably ought to look at powering the MayaPro separately, via the two +5V
and two ground pins in the 30-pin connector. This would remove the power
negotiations from the USB enumeration, and take the MIC2026 chip (TS-7260 ) out
of the picture.
>
> Do you know if the 2.6 startup behavior might not turn on USB power until
> the drivers are in place?
I think that they don't turn on *high* power until after enumeration. I don't
know how the Cypress or 8051 chip in the MayaPro handles its current draw if it
boots before the ts7260 boots and is ready to enumerate. That might be the
root of your 690 mA / 2.7V condition.
But, looking at the TS-7260 schematic, I don't see how it could make a
distinction between high & low power: there is just one switch (MIC2026) for
USB_5V, which is turned on as soon as EN_USB_5V from the FPGA goes high.
regards, ......... Charlie
>
> --- In "charliem_1216" <charliem_1216@> wrote:
> >
> > --- In "wrsimpson.alaska" <wrsimpson.alaska@>
> > wrote:
> > >
> > > We are using a TS-7260 SBC to control an Ocean Optics spectrometer (a
> > > MayaPro) and are having problems with the USB system. The problem has to
> > > do with the fact that the MayaPro consumes very near the USB limit of
> > > 500mA. It appears to exceed significantly (>600mA) during power-on of
> > > the USB device.
> > >
> > > The first problem I had was that the internal 5V charge pump cannot
> > > deliver this much current. I solved this by plugging the TS-7260 into a
> > > regulated 5V supply and inserting JP7, which then directly puts the
> > > regulated 5V to the USB power. This helped a lot, but didn't solve the
> > > full problem.
> > >
> > > Now, I see the USB device in two different power states. When plugging
> > > in the device or turning on the computer, I sometimes see one or the
> > > other state. One is the "normal" working state, where it draws 470mA and
> > > has a voltage across the USB nominal 5V of 4.6V. I think the voltage
> > > drop is partially on cables, contacts, and possibly the MIC2026 chip on
> > > the TS-7260. The other power state is "high current", where the USB
> > > device draws 690mA, but only has 2.7V voltage across the nominal 5V. I
> > > believe the other 2.2V is dropped in the MIC2026 chip because that chip
> > > becomes very hot in this state. From looking at the MIC2026 data sheet,
> > > I believe that it has gone into overcurrent or thermal shutdown, which
> > > should only happen at 1000mA. It might be that the USB device spiked
> > > that high, but I don't know.
> >
> > Isn't that 500 mA per port?
> >
> > >
> > > Another funny observation is that when I start with the TS-7260 off and
> > > the USB device plugged in, here's what see upon power up. The TS-7260
> > > starts to boot, and the current of the USB device goes in the
> > > high-current state. The MIC2026 gets very hot. The TS-7260 boots fully
> > > into runlevel 3, and then when I load the USB modules, the USB device
> > > suddenly switches into its operational state (normal current). The thing
> > > that fixes the system is the loading of the module "insmod
> > > usb-ohci-ep93xx". The current goes normal right after loading this
> > > module. I have no clue what is happening here. Possibly that module
> > > momentarily interrupts the USB power and resets the USB device? Possibly
> > > the USB device is drawing a high current before it enumerates onto the
> > > USB system?
> >
> > You don't say which kernel you are using, 2.6 or 2.4. After 2.6.10, the
> > USB initialization method changed substantially. Don't know about 2.4, but
> > in 2.6 overcurrent conditions should be in the syslog.
> > >
> > > My question is if anybody has seen this problem before, and figured out a
> > > workaround.
> >
> > No, not myself. I do have a couple of drive enclosures that use two USB
> > ports: one power & communication, and a second for power only. Perhaps
> > that would be an option for you if you're running into a per-port
> > overcurrent. Another option would be to use a powered USB hub between the
> > TS-7260 and your spectrometer if you have space, and room in your power
> > budget. You may still need to use two connectors.
> >
> > regards, ......... Charlie
> >
> > >
> > > Thanks!
> > >
> >
>
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