The figure displays 1-Wire interface analysis window, beneath it there is an image with work screen area containing the timing chart of data channel (DQ), at that the measurement was performed at Fs =200 KHz but the figure displays the timing chart for Fs =50 KHz. Marker 1 is set to start reset pulse and the marker 2 is set to start bytes transmission 0xСС.

The upper part of 1-Wire windows contains an image of typical timing chart of 1-Wire interface. As in the timing chart the red lines imply that bus is moved to logical zero by master, blue ones - by slave and gray ones imply that the bus is moved to logical item by raising resistor. Beneath it there is the panel of the main settings incident to the analyzed interface. Before you start decoding it is recommended to set the names of the interface channels on the panel "Channels" of logical analyzer. If you set the name DQ, then it automatically appears in the field of data channel.

As is known from
1-Wire interface specification, the session starts when master sets the reset signal (low level of more than 480 mcs long) and then confirmation signal is set in 15-60 mcs (low level of 15-60 mcs long) if there is only one slave in the bus. Upon receiving the confirmation signal the master transmits one or more bytes, at that the high-order bits go first, slave responses master as required. As the session starts when DQ line goes from high to low logical level then it is expedient to turn on triggering as to the falling edge. Before you start measuring it may be well to turn off the analyzed device and then press the Start button and turn on the device. If triggering is set correctly then the start of timing chart has to concur with start of communication. For the normal timing charts decoding it is necessary that the sampling frequency is at least 200 KHz.

Upon taking the timing charts it is desirable to set the marker 1 to reset signal otherwise the nearest reset signal right to the marker 1 will be searched and then one session may be skipped. For detailed decoding and description of transmitted bytes you can select one of the standard devices supporting 1-Wire interface, of course if its instruction set is in agreement with the instruction set of analyzed device. There is only one type of devices - thermometers DS18x20/DS18x22 in the dropdown list that can be subsequently added by other devices.

Upon completing all such procedures you can start decoding when pressing the Decode button. Decoding results will be displayed in the table in hexadecimal format (Code) except for start and confirmation signal and in character format (Description). When double clicking on the selected cell with the decoding results the marker 1 goes to start of the corresponding element of 1-Wire interface.

 

< Back