Hey Charlie-
Thanks very much for the replies. I think that we will probably try to
supply power to the spectrometer on the external connector under the control of
a digital output from the TS-7260 SBC so that we can keep the spectrometer off
until the SBC's USB drivers are fully loaded. It is a kind of hacked solution,
but may solve the issue. I have inquired with the manufacturer with regard to
both the USB specification compliance and the possibility of supplying power
externally.
Thanks again,
Bill
--- In "charliem_1216" <> wrote:
>
> --- In "wrsimpson.alaska" <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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