User's Manual for Kritzel
Contents
1. eee WPT ye GEA tras i Gr 2073 titi sr 21 At time stamp 0x1E2 the scanner has detected more than one event on probe 6 This means the level on this probe changed at least two times In this example at least from 1 at time stamp 0x1CA to 0 back to 1 and again to 0 the final state at time stamp 0x1E2 There are different reasons for this to occur e The report interval is to long for the frequency on the probe lines e The USB FIFO was full While the firmware waits for new space in the FIFO it continues to collect events 1 12 2 Check Data Consistency This tool is only useful for the stored data set It was very helpful during the development of this project It could become helpful again when someone has trouble while using programs of this project kreitzel heck lt itille nane krt gt Reachime carca krom iile tese Likit Data file contains 214661 datasets No obvious errors detected 1 12 3 Display specific Reports This tool was developed to check the realtime capabilities of the current Linux RT Preempt patch To find specific reports showing for example a timing violation kritzel_select can be used With the help of kritzel_select you can set up two event sources and trigger results into raw data display if these events violates a given timing Run kritzel select help for the possible options 1 12 4 Creating a Histogram This tool was developed to check the realtime capabil2. From signal stimul 1 falling edge to signal answer 2 both edges Data sets over all 214662 Counted events 23733 Erroneous events 0 r Plese Collunas Tine ia lns second collium Count 8000 112 9500 291 10000 301 10500 S16 11500 198 12500 191 13000 154 15000 85 17500 69 20500 12 24500 2 The worst case in this example is about 25 us The graphical histogram can be found in figure 7 counts 400 375 350 325 300 275 250 225 200 175 i t ee NON ON n o onono 8000 9500 10000 10500 11500 12500 13250 15000 17500 20150 24550 time ns Figure 7 Histogram 1 13 Visualizing with gtkwave The application gtkwave can be used to visualize the data set in a more convenient way than kritzel_raw can do it To get a dataset in a file format that gtkwave can handle use the f vca option and redirection when running the measurement kritzel s 500 f ved gt test vcd Page 9 of 10 Note The file test vca will grow quickly and can be very huge To visualize this dataset run gtkwave and simply load the test vcd file Page 10 of 10
3. 1 1 2 tare loz2 wee CCl kreiczel l 1 2 f kritzal 1 1 2 configure a kritze Cimi mak kritzel 1 1 2 sudo make install Most things are done automatically by configure but there are some parameters that can control how to build the kritzel executable e enable debug Be more noisy and do more runtime checking Enabled by default You should disable this feature when you only use this program e enable krt_format This is the native format kritzel uses when it outputs data to stdout Don t mistake it with the compressed data format This is valid only for stdout e enable vcd_format This is a industrial format used by other tools and also by gtkwave Support of this format is enabled by default 1 5 Preparation on the Host s Side The FirstGeneration Kritzel works with a parallel to USB converter from the vendor FTDI The device is an FT245BM refer to http Awww ftdichip com This kind of device is supported since the Linux kernel 2 4 days When it integrates itself into the system it emulates a simple serial connection so every tool that supports tty communications can work with it When running udev on the host it creates for each connected FT245BM a device node in this form dev ttyUSBx The x part in this device node name will be a number starting at 0 It s possible to connect more than one device at the same time The FTDI device uses a 16 ms timeout value as d
4. here E Start button Pressing this button starts a measurement in interactive mode F Stop button Pressing this button stops a measurement in interactive mode G Data Loss LED Lights yellow when more events happen than reports can be transferred through the USB line e H USB connector 1 3 Man Page Run the program with kritzel options lt device name gt Options are e s lt value gt Define scan interval unit ns Default is 10 000 000 10 ms i lt value gt Define stimulus interval unit ns Disabled by default a lt value gt Define stimulus active time unit ns Default is 1 000 000 1 ms lt value gt Define stimulus active level 0 1 Default is 1 active high o lt basename gt Use this basename for all output files Default is test_ file t lt text gt Define the measurement title Default is Measuring r Start scan immediately else wait for the scanner s local start action f lt format gt Select the data format on stdout lt format gt could be e krt Kritzel s native format e vcd Industrial VCD format e lt no gt lt name gt Define a probe name lt no gt from 1 to 8 lt device name gt depends on the device node name udev gives your device If it is the only serial device usually it will be dev ttyUSBO 1 4 Installation To install the package ensure ibz is already installed on your system Page 2 of 10 wie je ie sar ikiesiew l
5. 1 User s Manual This chapter should help any new user to get his her FirstGeneration Kritzel to run 1 1 What is Kritzel Kritzel is a simple scanner for general purpose measuring of digital signals up to about 500 kHz It is host based so any data processing occurs at the host side Kritze only reports what is happening on the probe leads and when Figure 1 Building Blocks Visualizing with gtkwave Other features e Fullspeed USB USB powered no additional power supply required 7 input only probes 1 bidirectional probe PWM for stimulus application on external devices under test Two 3 3 V level probes 5 V tolerant six 5 V level probes Kritzel supports the VCD Value Change Dump data format so the results can be processed and visualized with gtkwave http gtkwave sourceforge net or similar applications 1 2 Device Controls Kritzel can be controlled by the host but also a measurement can be started and stopped locally at the device A few LEDs are showing the current state of the device Figure 2 shows the locations of these control items Page 1 of 10 G F E Figure 2 Controls and Connectors e A On LED Lights green when USB power is active B Ready LED Lights green when device is ready to be used and the start button E and stop buttons F can be used C Busy LED Lights red when a measurement is running D 8 Probe connectors plus one ground connector not shown
6. ach probe Other data processing applications can use this information kritzel s 4000 t This is a specific title dev ttyUSBO There is no length restriction for the title You only should avoid characters like and If you use them they will get replaced by _ and This restriction exists as these characters are used to separate fields in Kritzel s data files To define a name for each probed signal you can extend the command line like this kritzel s 4000 1 trigger 2 answer 8 interrupt dev ttyUSBO This will assign the name trigger to probe 1 answer to probe 2 and interrupt to probe 8 Probes 3 7 are still using their default names There is no length restriction for each name but you should avoid the same characters in the name as for the measurement title Each run of kritzel will store the event data into test file krt andtest file info If you are using the o command line option you can select a different basename than test file kritzel will extend this basename with krt and info by itself 1 10 Probe Protection USB Probe Kritzel Figure 5 Protection Scheme Page 5 of 10 All inputs are protected against electrostatic discharge ESD with a serial resistor and clamping diodes refer to figure 5 This will also clamp 5 V input signals at probe 1 and probe 2 But avoid to connect any low impedance source
7. andling large data sets It can start to display with an data set offset This option is n lt value gt lt value gt is a simple number When given kritzel_raw skips the first number reports before starting to display How to read its output F L 24 eS E Graal 149 2 24 G2 G25 E F95 24 F96D r2 F985 24 ie 1660 IST 342 ere First column is the time stamp It s displayed in hex format It s always 16 bit wide and overflows at OxFFFF The next columns are showing the states of the 8 probe signals at this time stamp from left to right Probe 1 to 8 The character represents a 0 low the represents a 1 high The third column in the example above is empty description see below The fourth column shows the times tamp difference to the previous report Note The time stamp is always in relation to the selected time resolution while scanning So if the time stamp value advances by one this could mean 500 ns 4 us and so on Lets explain the second row in the example above The report was generated at the time stamp 0x131 It happens 21 counts later than the previous report Probe 1 4 5 6 7 and 8 do not change their state Probe 2 changes from 1 to 0 while probe 3 changes from 0 to 1 Sometimes a row contains the third column mentioned above Page 7 of 10
8. efault to transfer data from its FIFO to the host if there are less than 64 bytes in it To speed things up this value should be decreased to 1 ms This can be done with a echo 1 gt sys class tty ttyUSB device latency timer Note Replace the with the correct number udev has given your Kritzel 1 6 How to measure Up to eight probes can be used to measure digital signals Two types of levels are currently supported e Probes 1 and 2 are using input stages with 3 3 V power supply So they are reporting levels below 1 0 V as 0 and levels above 1 5 V as 7 e Probes 3 to 8 are using input stages with 5 0 V power supply They are reporting levels below 1 2 V as 0 and levels above 2 1 V as 7 Connect as much probes as you want to observe signals and don t forget the GND probe Do not connect the GND probe to a low impedance source other than ground This may destroy your target Kritzel and your host immediately Connect Kritzel through the USB to your host A device like dev ttyUSBO should now should show up 1 7 Physical Connections If you prepare the probe cables in the same way as me you can do the connections in two ways Directly through header pins or through any kind of clip contact The micro clip contacts are very cool but also expensive Page 3 of 10 Figure 3 Direct connection through header pins left and through micro clips right 1 8 Start Measuring To start a measurement run at lea
9. ities of the current Linux RT Preempt patch While the scanner generates a stimulus at a specific rate for a target it scans the target s answers on a second probe If the stimulus is connected to an interrupt input the target can answer interrupt recognition on the second probe Based on this dataset you can create a histogram to measure the realtime capabilities of the target while running various loads on it The tool kritzel_histogram creates a histogram in ASCII format that can be used with gnu plot to get nice graphical histograms Example e The scanner outputs a 1 kHz signal on probe 1 This signal is fed into an interrupt input of our target The interrupt input is active low e The target s interrupt routine outputs an answer on a separate GPIO It toggles the GPIO whenever it received the interrupt and entered the handler routine This GPIO is connected to the scanner s probe 2 Start the test with kiiczel 500 i LOOOWOG a 200000 1 0 L timul 2 answer t Niesalliesims dev ttyUSBO Now run various loads on your target to measure its realtime capabilities When the measurement is done you can build the histogram for this test We are interested in the timing Page 8 of 10 starting with the falling edge of probe 1 interrupt and ending with both edge of the answer signal on probe 2 i Keiiczel Inisicog am b l 2 esit_tile lance Histogram realtime Reporting interval 500 ns
10. o granularity in parentheses 16 us 62 5 ns 128 us 500 ns 512 us 2 us 1 024 ms 4 us 2 048 ms 8 us 4 096 ms 16 us 16 384 ms 64 us After selecting the best stimulus interval the firmware searches for the nearest possible active time Refer to the values in parentheses for the granularity in each stimulus interval Based on these values the firmware will calculate the possible active time within the stimulus interval Example For the 16 384 ms stimulus interval it means the shortest possible active time will be 64 us Longer active times will be always multiples of 64 us 1 12 Data Processing The kritzel main program generates up to two data streams from the reports the scanner sends One Page 6 of 10 stream is a compressed one and always generated The filename is test file krt ora different basename when using the command line option o A second stream will be generated if kritzel found its stdout redirected This stream can be used to work live on the data All other data processing programs in this archive can work with the compressed file or the redirected stream 1 12 1 Simple Data Display kritzel_ raw displays the scanner data in a primitive way You can run this program on life data or on an already stored krt file Display life data kritzel dev ttyUSBO kritzel raw Display stored data keitzel raw lt iile mame krt gt kritzel_raw has an useful option when h
11. st the kritzel program on your host It needs only one parameter all other settings are using default values in this case The device node to get a connection to the Kritzel system kritzel dev ttyUSBO This will use a reporting cycle of 10 ms and stores all data into file test_ file krt and in addition some human readable info about this measurement in test_file info The Kritzel application doesn t do any data processing It only collects all events reported by the scanner and stores them to a file For any further data processing other applications are required that can work on the stored data To select another reporting interval than the default extend the command line options with s To geta reporting interval of 4 us change the command line to kritzel s 4000 dev ttyUSBO The reporting interval depends on hardware capabilities Not every interval is possible Kritzel selects the nearest possible interval automatically For the FirstGeneration Kritze these intervals are possible 500 ns 4 us 16 us 64 us Note The 500 ns interval is an internal interval only This means Kritze can detect events with this timing resolution But after an event detection the firmware needs 2 us to generate a report and forward it to the USB FIFO So the maximum external frequency is about 500 kHz Note also Kritze cannot generate reports permanently at this rate Because each report contains 4 bytes this would result in a 2 MiB s data ra
12. te which a full speed USB device cannot handle This means a short burst of a 500 kHz signal Kritze can handle until the FIFO is full The average external frequency Kritzel can handle permanently is about 250 kHz Page 4 of 10 1 9 What a Reporting Interval Means Each reporting interval has a time stamp and all events within this interval are collected and reported at the end of that reporting interval refer to figure 4 All events means all events on all signals and it includes if one or more signals change their level more than once in the same reporting interval If the latter case happens Kritze uses an event loss mark for these signals in this report If there was no event within a single reporting interval there will also be no report This keeps the data amount small in the cases where events happen at a low rate Time Time Time Time stamp stamp stamp stamp reporting interval reporting interval reporting interval A i event 2 Ai sAn PS s event ee LE a ee iN Ereta 3 22e oo Aa event 1 and 2 nothing gets event 3 gets get reported reported reported Figure 4 Reporting Intervals Note Due to hardware restrictions the reporting interval 500 ns will generate a report whenever a single event was detected no collection The hardware is not fast enough to detect more than one event in this short interval To distinguish all measurements later on you can give each a title and a name for e
13. to any of the probe inputs that will force the clamping diodes to do their work This will destroy at least the serial resistors If the input voltage is above 7 V all active devices will be damaged and as the last member in this chain your host computer 1 11 How to Stimulate When you set up the stimulus generation Kritze will enable its output buffer on probe 1 Note Currently only probe 1 can be a stimulus output All other probes are input only As probe 1 continues to be an input too the stimulus data will be part of the data set If there is something to measure in relation to the stimulus always select probe 1 as one of the edges to be used for the calculation Note Stimulus generation depends on the capabilities of the underlying hardware The FirstGeneration Kritzel uses an internal 8 bit timer generating the output stimulus So the stimulus interval and the active time depend on each other Active Level o Active Level 1 Active Time Stimulation Interva Figure 6 Stimulus Generation Overview You can define the stimulus interval with the i command line parameter the active time with a and the active level with 1 The stimulus signal is a simple PWM signal generated by an 8 bit counter with compare capability To set up the nearest value to the given one Kritzel s firmware first tries to find the best stimulus interval Due to only a few internal clock dividers the intervals are limited t
Download Pdf Manuals
Related Search