USBee AX Bus Decoders
I2C Decoder
AX-Plus and AX-Pro Only
This section details the operation of the I2C Decoder
function that is part of the Logic Analyzer application that comes with the
USBee AX. Below you see the application
screen.
I2C Decoder Specifications
|
I2C Clock Speed
|
up to 12MHz
|
|
I2C Data Decoded
|
Start,Stop,Ack,Nak,Data
|
|
Decoder Output Format
|
Text File
|
|
Decoder Location
|
Logic Analyzer and Mixed Signal Scope
|
I2C Decoder Details
The I2C bus decoder is part of the Logic Analyzer or Mixed
Signal Oscilloscope applications. You
can access these through the View menu.
You first must capture a trace of data that contains the
I2C bus signals, SDA and SCL. The I2C
bus is Open Collector, meaning that you must have an external pull-up resistor
on each of the SDA and SCL lines. You
most likely already have one on your circuit design.
Once you have the trace captured, you can then run the
decoder to extract the data. You can
select any of the eight lines for the SDA or SCL lines.
The protocol and data is then extracted to the text
box. You can then select, copy and paste
this data into any other program for formatting or processing.
SPI Decoder
AX-Plus and AX-Pro Only
This section details the operation of the SPI Decoder
function that is part of the Logic Analyzer application that comes with the
USBee AX. Below you see the application
screen.
SPI Decoder Specifications
|
SPI Clock Speed
|
up to 12MHz
|
|
Async Baud Rate
|
up to 12Mbaud in 1baud steps
|
|
Decoder Output Format
|
Text File
|
|
Decoder Location
|
Logic Analyzer and Mixed Signal Scope
|
SPI Decoder Details
The SPI bus decoder is part of the Logic Analyzer or Mixed
Signal Oscilloscope applications. You
can access these through the View menu.
You first must capture a trace of data that contains the SPI
bus signals, SS, SCK, SI and SO. Once
you have the trace captured, you can then run the decoder to extract the
data. You can select any of the eight
lines for the four protocol lines.
You can specify which edge the data lines are to be sampled
on (opposite of the data changing edge). You can also choose the output data format and how many bytes to write
out per line.
The protocol and data is then extracted to the text
box. You can then select, copy and paste
this data into any other program for formatting or processing.
Async Serial Decoder
AX-Plus and AX-Pro Only
This section details the operation of the Async Decoder
function that is part of the Logic Analyzer application that comes with the
USBee AX. Below you see the application
screen.
Async Serial Decoder Specifications
|
Async Baud Rate
|
up to 12Mbaud in 1baud steps
|
|
Decoder Output Format
|
Text File
|
|
Decoder Location
|
Logic Analyzer and Mixed Signal Scope
|
ASYNC Decoder Details
The Async bus
decoder is part of the Logic Analyzer or Mixed Signal Oscilloscope
applications. You can access these
through the View menu.
You first must
capture a trace of data that contains the Async bus signal. Once you have the trace captured, you can
then run the decoder to extract the data.
You can select any of the eight lines for the decode.
You can specify
the baud rate to 1 baud, select msbit or lsbit first, data/parity combinations
and output display format of your choosing.
Once the decode
button is pressed, the protocol and data is then extracted to the text
box. You can then select, copy and paste
this data into any other program for formatting or processing.
USB
Decoders
AX-Plus and AX-Pro Only
This section details the operation of the USB Decoder
functions that are part of the Logic Analyzer and Mixed Signal Oscilloscope application
that comes with the USBee AX.
The USB Decoder that is part of the Logic Analyzer can decode Full
and Low Speed USB. Since Full Speed
USB is 12Mbps signaling, the Logic Analyzer must run at 24Msps for the decoder
to work.
You use the X and O cursors to select the area you want to
decode, select Full or Low Speed and press USB Decode. It will then extract the protocol and show
what is happening on the bus. You can
choose to hide SOFs by unchecking the Show
SOF checkbox. You can also filter
the display to only show a certain Device Address transfers. Enter the device address you want to see in
the Only Show Address box. Nothing or zero in this box show all
transfers.
The time for the start of each of the transfers is shown at
the left of the output screen. This time
correlates to the waveform screen so that you can lineup the events.
Below you see the application screen for the Full and Low
Speed USB Decoder.
The USB Decoder that is part of the Mixed Storage Oscilloscope is limited to the Low Speed USB which runs at 1.5Mbps since the maximum sample rate
of the digital signals is 16Msps. This
is too slow for Full-Speed USB sampling.
The decoding is the same as the above function except that it only
operates at Low Speed USB. Below you see
the application screen.
USB Low Speed Decoder Specifications
|
USB
Bus Speed
|
Low Speed Only
|
|
USB
Data Decoded
|
Setup,Data0,Data1,Ack,Nak,In,Out,Ep,Address
|
|
Decoder
Output Format
|
Text File
|
|
Decoder
Location
|
Mixed Signal Scope
|
|
|
|
USB Full and Low Speed Decoder Specifications
|
USB
Bus Speed
|
Full and Low USB Speed Only
|
|
USB
Data Decoded
|
Setup,Data0,Data1,Ack,Nak,In,Out,Ep,Address, Standard
Device Requests
|
|
Decoder
Output Format
|
Text File
|
|
Decoder
Location
|
Logic Analyzer (Must run at 24Msps for Full Speed USB
decoding)
|
USB Decoder Details
The USB bus decoder is part of the Logic Analyzer or Mixed
Signal Oscilloscope applications. You
can access these through the View menu.
You first must capture a trace of data that contains the
USB bus signals, D+ and D-. Once you
have the trace captured, you can then run the decoder to extract the data. You can select any of the eight lines for the
two protocol lines.
Once you press the Decode button, the protocol and data is
then extracted to the text box. You can
then select, copy and paste this data into any other program for formatting or
processing.
The USB decoder parses out the Endpoints, Data PIDs, Device
ID’s and decodes the standard Endpoint 0 device requests.
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