Differences Between the OV511 and OV511+ Camera-to-USB
UPDATED: New text is in red
As you will see, there are not many differences between the OV511 and
the OV511+. Most of them are rather trivial, except for the new alternate
packet sizes. Anyway, here's what's new in the OV511+...
Compression engine is now claimed to do 8:1 compression, was 7:1 previously.
have heard that the compression engine is exactly the same though.
A framerate of 10-15 FPS in VGA mode is now claimed.
USB transfer rate is now 7.5Mbps vs. 8.0Mbps previously. I suppose this
is due to the change in packet sizes.
Suspend capability is now mandatory
Now has a built-in USB transceiver
A "switching power clock" has been added. It is used
to boost the USB-supplied power from 5V to 10V, but it is not used for
anything at the moment since the current OV511+/OV7620 eval board has a
separate voltage doubler IC that does this on its own. The 10V power is
used to run the 5V voltage regulator for the camera.
Added a "programmable LED control" capability. This allows software to
set a pin high or low, which could be used for an LED, or as the spec hints,
could be used as a programmable I/O pin. Things will get complicated
if manufacturers starts using this pin for things beside just an LED.
The 24MHz USB bus clock has been removed.
30h (ISO FIFO Size): Since the packet sizes of the different alternates
have changed (see below, under Descriptor Differences,) this register now
only goes up to 11110 (960 bytes,) and its allowable values are different.
Note that this value, both with the OV511 and the OV511+ doesn't include
the 1 optional byte packet number, so this would be set to 960 for a packet
size of 960 (without the packet number) or for a packet size of 961 (with
the packet number.)
50h (Reset): Bit 0 has been changed from "Software reset for UDC"
to "Software reset for flush." I don't know what difference this makes,
52h (Snapshot): An extra bit, 3, has been added. It is a read-only
snapshot status bit, whatever that means.
54h (Switching power clock output select): The frequency of the
switching power clock is set here, to 24, 48, 96, or 192 KHz.
55h (LED Control): This switches the pin LEDCTL (79) on or off,
for controlling an LED, or some other nefarious purpose.
idProduct in the Device Descriptor has changed from 0x0511 to 0xA511.
WmaxPacketSize has changed in all of the endpoint descriptors for the different
alternates, except in Alternate 5, where it is still 513. I will use this
to my advantage, since if this alternate is used, there is no significant
change needed to migrate to the OV511+. Here is a summary of the old and
new packet sizes:
|Size with OV511
|Size with OV511+
As you can see, the sizes 33, 129, 385, and 961 have been added, and
the sizes 992, 993, 768, and 512 have been removed. The even sizes were
worthless anyway so good riddance to them, and the new sizes give us a
better variety of data rates. 385 will be perfect for systems with two
cameras running simultaneously.
Copyright © 2000 by Mark McClelland. You have permission
to freely redistribute this document as long as this copyright notice is