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| author | Uwe Hermann <uwe@hermann-uwe.de> | 2012-06-15 15:21:06 +0200 |
|---|---|---|
| committer | Uwe Hermann <uwe@hermann-uwe.de> | 2012-06-21 00:05:20 +0200 |
| commit | 3cf771a5179d94a156bef1aa95d7e05411dc82e2 (patch) | |
| tree | 2908e133f8070821afb7f18dbe32d36a519bca6e /decoders/usb/__init__.py | |
| parent | c2937021535a0ef11f2905e47447da3b589c65e3 (diff) | |
| download | libsigrokdecode-3cf771a5179d94a156bef1aa95d7e05411dc82e2.tar.gz libsigrokdecode-3cf771a5179d94a156bef1aa95d7e05411dc82e2.zip | |
srd: usb: Add long description of the PIDs.
Also, add missing ones which are mentioned in the USB spec. However, not
all may be relevant for LS/FS signalling. But they're still useful to
have in the table, so we can output warnings like
"Warning: HS PID encountered, but device is FS???"
Diffstat (limited to 'decoders/usb/__init__.py')
| -rw-r--r-- | decoders/usb/__init__.py | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/decoders/usb/__init__.py b/decoders/usb/__init__.py index 1a16f8f..313c495 100644 --- a/decoders/usb/__init__.py +++ b/decoders/usb/__init__.py @@ -21,6 +21,8 @@ ''' USB (low-speed and full-speed) protocol decoder. +Electrical/signalling layer (USB spec, chapter 7): + USB signalling consists of two signal lines, both driven at 3.3V logic levels. The signals are DP (D+) and DM (D-), and normally operate in differential mode. @@ -41,6 +43,8 @@ Data is transferred at a rate of 1.5Mbit/s (low-speed) / 12Mbit/s (full-speed). The SE0 transmitted to signal an end-of-packet is two bit intervals long (low-speed: 1.25uS - 1.50uS, full-speed: 160ns - 175ns). +Protocol layer (USB spec, chapter 8): + Bit/byte ordering: Bits are sent onto the bus LSB-first. Multibyte fields are transmitted in little-endian order (i.e., LSB to MSB). |