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Pt.3: By Mauro Grassi Multi-Purpose Car Scrolling Display User Software Instructions & Features Descriptions In Pt.3 this month, we describe how the MultiPurpose Car Scrolling Display is connected to the car and used. It’s driven using a simple command-line program. W HEN YOU HAVE built and tested the PC boards and installed the driver and software as explained in last month’s article, you will then need to use the host program for calibration, to change preferences and to set up the features of the display. This is done using a PC (a laptop is preferable if the device is already installed in a car), a USB cable and the command line program for Windows: cardisplay.exe (downloadable from the SILICON CHIP website at www. siliconchip.com.au). 78  Silicon Chip There are many user-changeable settings but the software is organised into multiple-choice menus which should make it clear to use. We should point out that in most cases, the default values will not need changing – you can use them as they are. Aside from the main features described in the December 2008 issue of SILICON CHIP, there are several other features. These are battery protection (if using a car’s battery as the power source), dependent variables and limit condition messages. The latter are messages that, in the two scrolling display modes, will alert you when a variable is too low or too high. As previously mentioned, in Static Display mode, flashing and reversed modes indicate the limit conditions. With dependent variables, you can display temperature in both degrees Celsius and Fahrenheit. More generally, you can display the same reading in different units, or show a corrected speed reading, for example. When using the display in a car, with the car’s battery supplying power, you can enable battery protection to switch off the display when the battery level drops below a set minimum. The display will then go into standby mode with a current drain typically around 10mA. This mode is also recommended if siliconchip.com.au you want to use running totals that persist over many on/off cycles. Connecting Sensors The Car Scrolling Display can monitor up to six different sensors. For a Voltage/Resistance sensor, connect the output of the sensor to one of the four input channels on CON3 (referred to as AN0-AN3). For a sensor with a varying voltage (eg, oxygen sensor), you should connect its ground reference to pin 6 of CON3. For a sensor with a varying resistance (eg, thermistors), you should connect its other end to pin 1 of CON3 (+5V rail). For a Frequency/Duty Cycle sensor, connect the output of the sensor to one of the two input channels on CON2 (referred to as FQ0-FQ1). You should also connect the ground reference to pin 1 of CON2. If you want to measure fuel injector duty cycle, for example, connect the fuel injector signal to one of the input pins of CON2 – see Table 1. Connecting Relays & Buzzers If you plan on using at least one of the two digital output channels for switching a relay or buzzer on a limit condition (a reading that is too high or too low), you should connect the relay or buzzer to CON4. Note that if you are powering the Car Scrolling Display solely from USB power (+5V) then neither relays nor buzzers will work on the output channels, because they take their positive supply from pin 4 of CON1 (the power supply input pin). Using USB power only does allow you to do everything else though, including data logging and powering the display. There are two relay/buzzer outputs, referred to here as Output 0 and Output 1. Output 0 corresponds to pins 1 (-) and 2 (+) of CON4 while Output 1 corresponds to pins 3 (+) and 4 (-) of CON4. For relays, which are not polarised, the coil is connected across pins 1 & 2 or across pins 3 & 4. You should connect buzzers with the correct polarity, however. Connecting The Supply There are two options when connecting power. One way is to connect the ignition-switched +12V supply from your car’s battery to pin 4 of CON1 while connecting the negative terminal of the battery to either pin 2 or 3 of CON1 (it is immaterial which). siliconchip.com.au Physical Channel Physical Input Pin Measurement Type 0 (AN0) Pin 5 of CON3 Voltage/Resistance 1 (AN1) Pin 4 of CON3 Voltage/Resistance 2 (AN2) Pin 3 of CON3 Voltage/Resistance 3 (AN3) Pin 2 of CON3 Voltage/Resistance 4 (FQ0) Pin 2 of CON2 Frequency/Duty Cycle 5 (FQ1) Pin 3 of CON2 Frequency/Duty Cycle Table.1: this table shows the pin-outs of the six channels. You connect the output of your sensor to either CON2 or CON3, depending on whether it is a voltage/ resistance sensor or a frequency/duty cycle sensor – see text. You then connect the positive battery terminal to pin 1 of CON1 (for battery level measurements). With this configuration, the “off” state current drain (the current drain when the Car Scrolling Display has shut down) is very small and is essentially determined by the 66kΩ loading on the battery sense input (the input impedance of the ADC input, which is very high, is in parallel with the 10kΩ resistor). It works out to be roughly 200μA. Unfortunately, with this power supply connection, three features of the Car Scrolling Display will not be available: battery protection, automatic shutdown and wake-up, and persistent running totals (see below for explanations of these features). For cars that are driven frequently, say at least once a week, and to ensure all features of the Car Scrolling Display will function correctly, you should reverse the positive supply connections. In other words, connect the (unswitched) +12V battery line to pin 4 of CON1 and the ignition-switched +12V to pin 1 of CON1. The only penalty is that when the Car Scrolling Display shuts down (for example, when you switch off the ignition), the display will still draw standby current – around 10mA. If that is a problem, you will need to connect the display to the car’s battery in the alternative way described above. Connecting A Computer The next thing to do is to connect the Car Scrolling Display to a computer running Windows, using a USB cable. You can do this at any time to change settings, calibrate the sensors and to do real-time data-logging. In last month’s article, we guided you through the installation of the Windows Driver, and the PC host program. You may want to create a short- Fig.1: this screen grab from Windows XP shows the properties of the command prompt shortcut used with the program cardisplay.exe. We suggest you use size 16 Lucida Console font, while the window width should be 125 and the height 58. cut to the command window to go on your Windows Desktop. The guggested settings are shown in Fig.1. Change these by right clicking on the shortcut icon and going to “Properties”. The line width should be at least 120 characters, as the program can output some very long lines, which will otherwise wrap around and be difficult to read. When cardisplay.exe is run without command line options, it will display the help message listing the available options. The full list of command line options is shown in Table.2. Setting Name & Unit Strings Each of the four values of each variable has an associated name and unit string. The default name strings are of the form VarD(N) where D is the February 2009  79 Fig.2: typical limit condition messages in the two scrolling modes. When a reading is below the minimum or above the maximum, you will periodically be warned about this. You set the minimum and maximum values by running the command cardisplay -v and choosing the “Change the Minimum & Maximum Values & Hysteresis” option. variable number (0-5) and N is the value number (0-3). For example, the default name of reading 2 of variable 3 is Var3(2). The default unit strings are similarly of the form UnitD(N). For example, if you are measuring engine RPM, you could choose the name “Engine Revs” and the unit “RPM”. To do this, run the command: cardisplay -v and choose the “Change the Name and Unit of the Variable”. Once you’ve chosen the variable name and its units, select the “Exit and Save” option and they will be saved to nonvolatile memory. Remember that you will also need to add the reading to the display queue as explained in the section titled “Changing The Displayed Readings & Their Order” (see below), for it to be displayed. Setting Minimum & Maximum Values Fig.3: this screen grab was obtained by running the command cardisplay -o. It shows the output configuration menu and this is used to set up the two digital outputs to drive buzzers or relays, depending on limit conditions. In this example, the second output is disabled, while the first output controls a relay that will switch off when the battery voltage drops below 11.0V. Fig.4: how to use the command cardisplay -o to set up a relay connected to Output 1. In this example, we have followed the prompts to set up the relay to switch on when the battery voltage exceeds the set maximum value of 13.8V. The choices are made at each step by pressing the appropriate key (we’ve selected options b, b, a, g & d here). Choose “Exit & Save” for the changes to take effect. 80  Silicon Chip Next, you can also set the minimum and maximum values for the reading, by running the command cardisplay -v and choosing the “Change the Minimum and Maximum Values & Hysteresis” option. Visible cues depend on the minimum and maximum values you enter. Recall from the first part of the article, that in the Static Display mode, the readings will flash when below the minimum and flash reversed when above the maximum. In the other two scrolling display modes, there will be periodic warning messages as shown in Fig.2. If you are also planning to use one of the two digital outputs to monitor a reading and have a relay switch on or off or a buzzer sound on the extremes, these are also the values that determine the on/off switching of the relay or buzzer. For example, for a 12V car battery, a typical minimum value would be 11V and a typical maximum would be 13.8V. For cabin temperature, you might choose 16°C for the minimum and 32°C as a maximum. If you would like to monitor a reading and have a relay switch on or off on a limit condition, or have a buzzer beep, you should configure one of the two digital outputs as follows. Setting Up A Relay Setting up a relay to switch on or off on a limit condition is easy. Run the command cardisplay -o to enter the output configuration menu as siliconchip.com.au Command cardisplay or cardisplay –h cardisplay –x:N or cardisplay –q:N cardisplay –v (‘v’ is for variable) Function Example Show all available command line options (help). View real time information from variable number N, where N is in the range 0-5. The –x option is useful for troubleshooting cardisplay The available command line options will be shown. cardisplay -q:0 Shows information on variable 0 including all real time readings. Go to the variable setup menu. cardisplay –d (‘d’ is for display) Go to the display menu. cardisplay –v cardisplay –d Result You can change all variable settings, like minimum and maximum values, enable or disable averaging mode, change the name and unit strings for the variable, among others. You can change which readings are displayed and in what order, among other things. The menu options are listed in Fig.6. cardisplay –i (‘i’ is for information) Display Information about the Car Scrolling Display, including system settings cardisplay –i Displays the current values of the settings, including system settings. cardisplay –e (‘e’ is for extended) Display extended information about the Car Scrolling Display. cardisplay –e Displays extended information including internal settings useful for troubleshooting, if needed. cardisplay –c (‘c’ is for calibration) Go to the calibration menu. cardisplay –c Follow the on screen prompts. cardisplay –o (‘o’ is for outputs) Go to the output configuration menu. cardisplay –o Start real-time data logging up to N samples or until interrupted by the user. Start real-time data logging up cardisplay –l:N:<filename> to N samples and store as file <filename> in .csv format. to the system settings cardisplay –s (‘s’ is for system) Go menu. Write all settings to a file for cardisplay –w:<filename> later recall. Read all settings from a cardisplay –r:<filename> previously created file. Reset the Car Scrolling Display cardisplay –r and restore all default values. cardisplay –u:N cardisplay –u:100 Cardisplay “–l:2000:my Data Log” cardisplay –s Allows you to configure the two digital outputs for connecting relays or buzzers. The menu options are listed in Fig.4. Capture 100 samples in real time at the set logging frequency and dump the data to a .csv file – see Fig.9. Capture 2000 samples in real time at the set logging frequency and dump the data to a file. Change any system settings. The menu options are shown in Fig.5. cardisplay “-w:mySettings” Saves all settings to the file mySettings. cardisplay “-r:mySettings” Restores all settings from the file mySettings. Resets the car scrolling display and restores cardisplay –r all default values. Table.2: this table shows the command line options for the PC program “cardisplay.exe” running on your Windows OS. You can use a laptop to connect to the Car Scrolling Display if it is already installed in your car. You will need a USB cable and the PC host program will allow you to log your car’s signals in real time. shown in Fig.3. Note that the current settings of the two digital outputs will be shown. Choose the “Set Up a Relay” option. Then choose the digital output connected to the relay you wish to control. You then select one of the four operating modes: (a) Relay switches on at a maximum condition. (b) Relay switches off at a maximum condition. (c) Relay switches on at a minimum condition. (d) Relay switches off at a minimum condition. You then choose the variable to monitor and the relay output will be set up. A complete procedure is shown in the screen grab of Fig.4. siliconchip.com.au Note that each variable has its own hysteresis value (shown as a percentage) which is settable by running the command cardisplay -v and choosing the “Change the Minimum and Maximum values & Hysteresis” option. A typical value will be 10%. This affects how a relay connected to one of the two digital outputs is switched on or off. Suppose for example, that the minimum and maximum values for the battery voltage are set at 11.0V and 13.8V respectively, with the hysteresis at 5%. If the relay is set to switch on at a maximum condition, then the relay will switch on whenever the battery voltage is above 13.8V and switch off whenever the battery voltage is below 95% of the maximum value, ie, below 13.1V. Setting Up A Buzzer Again, run the command cardisplay -o. This time, select the “Set Up a Buzzer” option, then choose one of the two digital outputs and the variable the buzzer applies to. Remember that the buzzer will emit two short beeps when the reading is below the minimum and one long beep when the reading is above the maximum. Recall also that beeping is only enabled in the Static Display mode. Changing System Settings There are a few system settings which can be set by running the command cardisplay -s. You will be given February 2009  81 Fig.5: this shows the result of running the command cardisplay -s to change system settings. The value of the setting is shown and you are prompted to enter a new value. In each case, pressing ENTER retains the old value. For the Enable/ Disable settings, you press either e (for Enable) or d (for Disable). When the settings have been entered, the new settings are displayed. in Static Display mode when a limit condition occurs. The smaller the number, the shorter the time that the reading will be seen. (c) Readings Rounding Off Mode: you can enable or disable rounding off of readings. If enabled, rounding will be applied to all readings, depending on how many digits after the decimal point are set for that variable. For example, if a variable is set to show two digits after the decimal point and the reading is 123.5565, the display will show 123.56 (with rounding enabled) rather than 123.55 (with rounding disabled). (d) Zero Accumulators at Power On: you can enable or disable setting all accumulators to 0.0 when the display is powered on. Disabling is useful if you want persistent running totals, ie, totals that retain their value when you switch off the ignition. (e) Automatic Wake-Up On Battery Sense: enable this to have the display turn on automatically when power is detected at the battery sense input. (f) Readings’ Update Frequency (Log­ ged): you can set the readings’ update frequency for data logging from 0.2Hz to 8Hz. Note that the readings’ update frequency for normal display mode is always half of this value. Display Settings Menu Fig.6: by running the command cardisplay -d, you can enter the display settings menu. Here you can add readings you want to show or hide readings you no longer want to display. You can also change the order of the displayed readings, the scrolling speed of the display and the minimum and maximum brightness levels. the current value of each system setting and prompted to enter a new value. In all cases, pressing ENTER retains the current value. Again, in most cases, the default system settings probably will not need to be changed. A typical screen grab is shown in Fig.5. Note that some are Enable/DisFig.7: this is the message that will scroll when the battery level drops below the set minimum. The Car Scrolling Display will protect the battery by shutting down to standby mode. 82  Silicon Chip able settings and you simply type ‘e’ or ‘d’ to enable or disable respectively. The system settings are: (a) Minor delay: this is a number in multiples of 16ms that sets the delay for flashing and reverse flashing in Static Display mode. The smaller the number, the shorter the time that the readings will be off (if flashing to indicate minimum condition) or reversed (if flashing in reverse to indicate a maximum condition). (b) Major delay: this is a number in multiples of 16ms that sets the time that the actual reading is displayed Once you’ve set up a variable, you can select which readings to display using the display settings menu. You can also select the order in which the readings are displayed, the minimum and maximum display brightness and the scrolling speed. Ambient Light Level Response The ambient light level is used to automatically dim the display when the light level drops. This can be overridden by setting the minimum and maximum brightness levels. The higher the number, the brighter is the display. If you set the minimum to be equal to the maximum, then the brightness will be fixed. If, for example, you set the minimum to 100 and the maximum to 250, the brightness will vary between these extremes, depending on the ambient light level. It is usually desirable to have a dimmer display when the am- siliconchip.com.au bient level drops. It will also result in lower current drain. The scrolling speed (applicable to the two scrolling display modes) can be varied. The lower the scrolling delay (measured in milliseconds), the faster the scrolling will be. To set the minimum and maximum brightness as well as the scrolling speed, run the command cardisplay -d and choose the “Change Display Settings” option. Changing the Displayed Readings & Their Order The display menu also allows you to select up to 10 readings to display and choose the order in which they appear. Note that the first reading cannot be hidden, so there will always be at least one reading to display. The accumulator of each variable can also be displayed. When the accumulator is displayed in any of the two scrolling modes, the name string will be that of the value which it is summing with a ‘(+)’ suffixed to indicate that the accumulator rather than the value is being displayed. To change which readings are displayed and in what order, or to hide or add a reading, run the command cardisplay -d and choose the appropriate options as shown in the screen grab in Fig.6. For example, choose “Change Order of Display Object” and select an object from the list of currently displayed readings. Then use the arrow keys to move the reading up or down in order. Battery Protection, Automatic Wake-Up On Battery Sense With the correct power supply connection, you can enable automatic wake-up on battery sense and battery protection. Recall that the Car Scrolling Display will go into standby mode (drawing only very small currents) when it detects that the battery voltage has dropped below the minimum (it will, however, not go into standby mode if USB power is available). The delay from detecting the low battery condition to the Car Scrolling Display shutting down (with a message as shown in Fig.7) can be set by running the command cardisplay -s. siliconchip.com.au The setting to change is the “Battery Protection Delay”. This delay is useful, for example, if you are running a cooling pump from a relay on the digital outputs and you want it to operate for a while after the ignition key has been switched off. When you enable automatic wakeup on battery sense, the Car Scrolling Display will turn on when it detects that the battery level is above the minimum. You can enable or disable this by running the command cardisplay -s. The setting to change is “Automatic Wake Up on Battery Sense”. Note that when you see the message in Fig.7 and the Car Scrolling Display goes into standby mode, you can manually force the display to wake up by pressing the pushbutton on the front panel. Keep it pressed for 10 seconds or so and the display will turn on. System Messages From time to time, you will see a number of messages scroll by on the display which are generated by the firmware in response to a number of events. These are shown in Fig.8. Real Time Data Logging For data logging, run the command: cardisplay -u:<N> or cardisplay -l:<N>:<filename>, where <N> is the number of samples and <filename> is the name of the file to save the data to. Fig.9 shows an example screen grab. Note that when specifying a command line option with spaces, you use double quotes to enclose the argument. For example, to collect 2000 samples and store the result to a file called “My Output Log” you would type at the command prompt cardisplay Fig.8: these are some system messages, which begin with a “>” character. “Wait” appears when the display is busy; “Logging” when entering data logging mode; “USB On!” when a USB cable is connected; “USB Off!” when a USB cable is disconnected; and “Reset” when a reset has occurred. “Off” indicates that you have scrolled past the last reading and that the display is about to turn off (but not go into standby mode yet). “-l:2000:my Output Log”, enclosing the argument in double quotes. The produced file will be a .csv (comma separated values) file which can be opened with any spreadsheet. Only values which have been made loggable will be logged at the set logging frequency. To change the loggable values of a variable, run the command: cardisplay -v and choose the “Set the Logging Parameters For the Variable”. You Fig.9: this screen grab was taken after running cardisplay -u:100 to collect 100 samples in real time. The battery level and the ambient light level are being logged at the logging frequency of 5.6Hz. When using the -u option rather than the -l option, the filename is generated automatically from the PC’s date and time. In this case, the log was saved to dataWedDec171647472008.csv. February 2009  83 Fig.13: In the Static Display Mode, overflow is indicated by 4 ‘+’ signs, while 4 ‘-‘ signs indicate that the reading is not ready to be displayed. In the scrolling modes, the value will appear as ‘N/A’ when the reading is not ready to be displayed. running the command: cardisplay -v and choosing the “Change Welcome Message” option. Saving & Restoring Settings To A File Fig.10: this shows the result of importing the log file into the spreadsheet application Microsoft Excel. We’ve also created a graph of the battery voltage level. This shows that the battery voltage was switched on around 4s after the start of logging and switched off again at about the 15s mark. can choose to toggle whether each of the four values of the variable will be logged. If at least one value is made loggable, you can further choose to log the accumulator for the variable and to log the limit conditions. A screen shot showing a log file that has been imported into Microsoft Excel is shown in Fig.10. Here, the battery level has been logged and a graph has also been created. Out Of Range Values In Static Display Mode, out of range values will be shown as four “+” signs. When a displayed value comes from a variable that has not been updated since being last displayed, the value will appear as “N/A” in the two scrolling modes and as four “–” signs in the Static Display mode (see Fig.11). Changing The Welcome Message When the Car Scrolling Display first powers on, a welcome message is shown. The default welcome message includes the firmware version. You can change the welcome message by To write settings to a file for later restoring, run the command cardisplay -w:<filename>. You can restore settings by running the command cardisplay -r:<filename>. Restoring Default Values To restore all default values, as well as clearing all strings, you run the command cardisplay -r. That completes our presentation of this project in the magazine. To obtain more detailed information about the operation of the software and the calibration procedure, as well as how to change the variables’ settings, you can access a PDF file entitled “Car Scrolling Display User Guide” on our SC website. 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