Fullscreen HTML5Med Res (??MB)HTML4

Universal USB Data Logger; Pt.3 In this third and final article on the USB Data Logger, we describe how to use the accompanying Windows host software. This software allows you to edit and test scripts, upload them to the logger and change its settings. By MAURO GRASSI A S EXPLAINED previously, scripts are used tell the Data Logger which sensor(s) are attached, how to query them, what the readings mean, how often to log the data and the data format to use. If you have not already prepared a memory card, you can format it with a FAT or FAT32 file system (a quick format is OK) before plugging it into the Data Logger, with the power off. Having installed the host software and driver (see Pt.2), plug the Data Logger into your PC and launch the software by double-clicking the .exe file. What the software does Essentially, the Windows host software is a “development environment” which allows you to write scripts, upload them to the Data Logger and test them. It also allows you to monitor scripts as they run and download logged data over the USB interface. In addition, you can change the Data Logger’s settings from the host software. Since complex scripts can be difficult to debug when running on the Data Logger itself, the software allows you to “simulate” the scripts, running them on the host PC to see what they 76  Silicon Chip do. Scripts can be simulated at an accelerated rate which is useful for those scripts which involve long delays. Note that because simulated scripts are run on the host PC, they can not access the sensors as they can on the Data Logger. For example, if a simulated script reads from an analog input, the result is always zero. User interface The interface for the Windowsbased host software is shown in Fig.11. When plugged into a USB port, the Data Logger is detected automatically. Its firmware version and the connection status are shown in the window title bar, at top. The main window has a number of sub-windows. The script editor sub-window is at upper left and this is where scripts can be created or modified. The log sub-window below it allows you to keep track of program actions as they take place. There are some buttons between the two which clear the log window and perform other common actions. At lower right is the console subwindow, which has a grey background. It allows you to see what a script is log- ging as it runs or is simulated, which is useful for testing complex scripts (more on that later). Above the console are several buttons, used to control the simulation. At far upper right are the Data Logger settings and below them the Host Settings, which apply to the PC host software. To the left of the settings are four additional sub-windows (two red, two green) which allow you to see the files and scripts stored on the Data Logger and on your host computer (respectively). They also allow you to manage scripts, including transferring them to and from the Data Logger. Settings The device settings (at upper right of Fig.11) are stored on the Data Logger, both in a file on the memory card and in its internal FLASH memory. If the file on the memory card becomes corrupted or the card is removed, the Logger relies on its internally stored settings. Otherwise, the settings on the memory card are used. You can copy the settings between the Data Logger and the host PC via the Host and Device menus. It is also siliconchip.com.au Fig.11: this is the user interface for the PC host software. This lets you edit, compile and upload scripts to the USB Data Logger via the USB interface. It also allows you to change settings and to download log files. possible to restore the settings to the defaults using these menus. They work as follows: Auto Time: when enabled, the PC host automatically sets the real-time clock in the Data Logger whenever they are connected. Without this option you can synchronise the time manually via the “Time” menu. System Log: when enabled, the Data Logger will note special events in a log file on the memory card (syslog. txt). This is useful for troubleshooting but slows the Data Logger down and increases its power consumption. The contents of this file can be read or cleared through the host software via the Device menu when the Data Logger is plugged in. System Log USB: when enabled, as well as logging to the “syslog.txt” file on the memory card, the Data Logger also sends system log messages over the USB serial interface and the host software diplays them in the console sub-window. Undervoltage: when this is enabled and the battery voltage drops below the specified level, the Data Logger goes into sleep mode, minimising power consumption. This is recommended siliconchip.com.au in order to avoid over-discharging the battery. Remember that this voltage does not take into account the voltage drop across the Schottky diode from the battery (the default setting is 1.8V as shown). menu to provide the best legibility with your display. If you are using a third-party text editor, the easiest way to upload the script is to paste it into the text editor window and then proceed from there. Editor window File browser You can use any text editor you like to write scripts but for convenience, the host software has a built-in editor, allowing small script changes to be made and then immediately simulated or uploaded to the Data Logger for testing. The script is shown in the upper left window and most of the associated commands are located in the “File” menu above it. The editor font size can be changed via the “Window” As mentioned, the two red and two green sub-windows towards the upper right are the file and script browsers. The red windows show directories, log files and scripts on the Data Logger while the green windows show the same information for the host computer. Using these windows, you can browse the contents of both devices and transfer files between the two. In each case the left-most window Where To Buy Kits & PC Boards A complete kit of parts for the USB Data Logger is being produced by Altronics and should be available shortly after this issue appears. In addition, readers will be able to purchase the PC board from SILICON CHIP. This board is double sided, with plated through-holes and features a solder mask, FR-4 fibreglass substrate, tinning and 1oz copper tracks. The PC boards are available for $A25 (including GST) plus $A10 postage per order. Postage is $A12 to NZ or $A18 elsewhere. February 2011  77 Fig.12: this interface appears if the PC host software is launched with the bootloader running. This then allows you to update the firmware in the USB Data Logger. shows the file system directory structure and files (including log files) while the right-most window shows the loaded scripts (more on that later). Up to eight script files at a time can be loaded on the Data Logger and each is assigned a unique number, which is also shown. Local files are stored in the same directory as the host software. In both cases, the file lists are sorted alphabetically. Directories are shown in square brackets and directories and files can be opened by double-clicking them. Scripts are opened in the editor window. Right-clicking on a file gives a context menu with additional options. This includes options to initiate file transfers between the Data Logger and host PC. Note that while this is a very convenient way to access log files on the Data Logger, for large log files (15MB or more) it can be faster to remove the memory card from the Data Logger and use a USB card reader to transfer them instead. This is because the Data Logger’s USB transfer speed is limited by the PIC18F2753’s small amount of RAM (Random Access Memory) and modest clock speed. Compiling scripts Before a script can be tested or 78  Silicon Chip Fig.13: after selecting a hex file and clicking “Yes” (see Fig.12), the new firmware is uploaded to the logger and a progress bar is displayed at the bottom of the window. used, it must be loaded into the editor window and then compiled. When it is compiled, the software checks that the script is valid. If there is anything wrong with it, the Compile button turns red, one or more error entries appear in the log window and compilation is aborted. If errors are reported, the first invalid line in the script code is highlighted. The location of the error is also shown in the log sub-window, as a line and column reference. Once the problem has been fixed, you can attempt to compile the script again. The compiler can also generate “warnings”. As with errors, these are noted in the log sub-window but they do not prevent successful compilation. If present, these warnings indicate possible errors in the script but they can sometimes appear when the script is correct. If the script is correct (ie, there are no errors), the Compile button turns green and the script is added to the list of available local scripts. Rather than pressing the “Compile” button you can also press the F10 key on your keyboard. The compiled script can be transferred to the USB Data Logger by right-clicking on it in the green “Host Scripts” window and selecting “Send PC Script”. For con- venience, you can press F11 instead which compiles the script and then automatically sends it to the Data Logger, assuming the compilation was successful. You can also send all local scripts to the USB Data Logger by pressing Shift+F11. There is a handy help window at the right of the user interface (with a grey background) which lists all defined constants, global functions and global variables in the script. Each global function is listed with a number in parentheses indicating the number of arguments that the global function takes. Global define constants are shown with their values, while global variables are shown with their size. The “Optimize Code” option, above the log window, is enabled by default. This allows the compiler to remove any redundant portions of the script or simplify it where possible. This reduces the memory and processing required to run a script on the USB Data Logger. Simulating scripts Once a script is compiled, it can be simulated in the console sub-window (lower right of Fig.11) using the Run, Stop, Reset and Step buttons. Pressing Run begins the simulation and the script output is shown in the console siliconchip.com.au window (this would normally be stored in the log file on the memory card). If you click Stop, the script pauses and the next line about to be executed is highlighted in the editor window. You can then use the Step button to proceed through the script, one line at a time. This is good for debugging since you can observe the program flow and see the log output from each individual line in the script. The Reset button can be used to start the script from scratch and the Clear Console button blanks the console sub-window. During simulation, the Scale Time option can be adjusted (upper right) to change the speed at which the simulation runs. For example, if Scale Time is enabled and set to 10, a scripted delay of 25 seconds actually takes 2.5 seconds. This makes debugging scripts with long logging periods far less tedious. You can also use the console subwindow to observe data being logged to the memory card in the Data Logger as it occurs. This is useful for the final test of a script, with the actual sensors attached. Status bar The status bar, at the bottom of the window, indicates what the host software is doing at any given time. This shows USB data transfers, the time from the Data Logger and so on. At the right of the status bar are two flexible displays which can show various statistics, which are selected by clicking on that portion of the status bar. The first (left-most) flexible display shows information about time synchronisation while the second shows various voltages from the Data Logger, including the supply and battery voltages. Updating the firmware The Data Logger’s firmware (the software running on the microcontroller) can be updated from the host computer over USB. To do this, first you must activate the bootloader by holding down S2 on the USB Data Logger while applying power (normally from USB). To do this, the battery must be removed as there is no way to switch it off. With the bootloader activated and the Data Logger plugged into the host PC via the USB port, launching the host software will display the bootloader interface instead of the siliconchip.com.au Tips For Installing The USB Driver Here’s a tip for installing the USB driver. The USB Data Logger will go into standby (and detach from the host PC’s USB interface) when there are no custom scripts loaded. This is done to save power and since initially there are no scripts loaded, this will be the state of the USB Data Logger after it is first switched on. As this can affect the installation of the driver (since the USB connection may be lost during the driver installation), it is advisable to install the driver with no memory card inserted in the socket. When switched on, if no memory card is present, the USB Data Logger does not enter standby as quickly as it does when a card is present. This gives you around two minutes to plug it in and install the driver, which should be long enough in most cases. If not, you can always press S2 to keep it out of standby for another five seconds. This feature is provided as a fail-safe feature in case the USB Data Logger is used with a very old system. usual development environment (see Fig.12). In bootloader mode, the blue LED (LED3) flashes at around 1Hz. Once the USB interface has been recognised, the flash rate increases slightly and is faster again when the firmware is being read or written. Typically, firmware updates are supplied as a hex file (.hex file extension). You can then use the “Write HEX” option to transfer this file’s contents contents into the microcontroller’s FLASH memory (Fig.13). It will check that the file is valid, then ask you to confirm that you want to overwrite the existing firmware. After rewriting the program memory, a verify operation is automatically performed to ensure that it was successful. Note that if you subsequently use the Data Logger and then attempt to verify the firmware manually using the Verify Memory button, the verification will fail because the Data Logger also uses the FLASH memory to store its settings. This also means that updating the firmware resets the Data Logger’s settings to its defaults. Using the logger When operating, pushbutton S2 and blue LED3 are used to control logging and provide feedback. A short press of S2 tells you the logging status: LED3 will flash once if at least one script is running or three times if there are no scripts running (and therefore no logging is taking place). A longer press of S2 pauses all scripts, in which case the logger flashes its LED three times to confirm that logging is paused. A second long press results in a single flash and logging resumes. The blue LED also flashes to indicate USB activity when the USB interface is in use by the host software. Standby mode The logger automatically goes into standby mode under the following circumstances: (1) When there are no custom scripts loaded. (2) When all the custom scripts that are loaded are paused or not running. (3) When there is a time delay of at least five seconds, during which no custom scripts need to run. (4) When the under-voltage protection is enabled and the battery voltage is below the set threshold. In standby mode, the Data Logger’s USB interface shuts down (the PC host will show it as being “disconnected”) and the LED glows dimly but does not flash. As mentioned in Pt.1 (December 2010), the full power savings will not be made unless the minimum logging period of all executing scripts is above the threshold for going into standby (five seconds). Below this threshold, the microcontroller does not switch off power to certain components, including the memory card, because otherwise the initialisation sequence would take too long. You will therefore get the best battery life if your logging scripts execute sleep periods of greater than or equal to this time. In standby mode, the current drain from the battery is around 560-850µA. If the battery voltage is very low, the PIC enters sleep mode which is at the February 2011  79 Errata Sample Excerpt From Syslog.txt Time Unavailable: USB Data Logger Version: 9.60. Global PORs: 4. Local PORs: 1. Time Unavailable: Memory Card Detected, Total Size: 2.0 GB Free Size: 2.0 GB. Time Unavailable: VM(s) Running: 1 of 2. Time Unavailable: The Following VM(s) Are Loaded: { oneScript, csvScript } lower end of this range (560µA) and it stays in sleep mode until the device is power cycled. This does not include the current consumed by any sensors powered from the Data Logger. Typically, sensors will not consume much power when they are idle but for long-term logging, even a small amount of additional power can reduce battery life. If the Data Logger goes into standby mode while plugged into USB, it will disconnect from the host PC (it won’t do this if the host program is running). Pressing S2 or inserting a memory card brings the Data Logger out of standby mode. While writing to the SD card, instantaneous power consumption from the battery can be 25mA or more but if the scripts have long sleep periods, this averages out to a much lower value in the long term. System log As mentioned earlier, the Data Logger can store events in a system log for troubleshooting purposes. A sample excerpt from the syslog.txt file, as created when the Data Logger is switched on, is shown in the accompanying panel. The first line shows the Data Logger firmware version and the number of power cycles (Power On Resets or PORs) that the USB Data Logger has undergone. The Global reading indicates full resets while the local reading shows the number of times the scripts have been reset by the software. This can happen if the memory card is removed. The second line shows information on the memory card while the third shows how many virtual machines (VMs) are actively running scripts (there are up to eight). The fourth line shows the names of the scripts that are loaded. Here are some more example system log entries: Thu 23 Dec 2010 05:42:01: Destroy 2 VM(s). Thu 23 Dec 2010 05:42:11: Holding. The first line indicates that two scripts were reset, resulting in their virtual machines being “Destroyed”. The second indicates that script execution has been paused by a long press on pushbutton S2. Digital sensor requirements When using an input for frequency or event counting, you must make sure the signal is within 0-5V (for D0-D3) or 0-3.6V (for D4 & D5). For I2C sensors, their SCL (clock) line must be connected to D0 and the SDA (data) line to D1. While the pin connections for the I2C bus are fixed, multiple scripts can access sensors on the one bus. One Wire sensors can connect to any of the six digital pins D0-D5. You must configure the correct pin number in the script. The same applies to the serial port; you specify the Transmit and Receive pin numbers, the baud rate and the mode. The serial port supports baud rates up to 0.5Mbps. Multiplexed peripherals While the PIC18F27J53 microcontroller has just two serial peripherals, each of the eight possible scripts can configure its own serial port with whatever configuration it requires (pin connections, baud rate, etc). The PIC’s To improve filtering of the +3.3V supply rail, the 22µF tantalum capacitor on the output of REG1 should be changed to a 220µF 10V low-ESR electrolytic (Jaycar RE-6300). This change applies to both the circuit diagram in Pt.1 (December 2010, page 38) and to the overlay diagram in Pt.2 (January 2011, page 35). Note that there are two 22µF tantalum capacitors shown adjacent to REG1 on the overlay. The capacitor on the left is the one to change. The parts list in Pt.1 should be amended accordingly. peripheral pin select (PPS) feature allows the software to re-map the UARTs as appropriate for each script as it runs. This is the same feature which allows One Wire sensors to be connected to any of the I/O pins. For example, you can have one custom script sending data to a serial port on pin D0 at 9600bps, while having another script sending data to an independent serial port on pin D1 at 115,200bps. The hardware state is saved and changed as required by the firmware for the currently executing custom script. As well as selecting the pin connections and baud rate for the serial port, scripts can choose to invert the receive or transmit logic or to have an open drain output. Writing scripts Finally, for those who build the USB Data Logger, we have prepared some detailed information on writing logging scripts, including a complete description of the language’s syntax and global functions and variables. This information is available as a PDF file from the February 2010 section of the SILICON CHIP website. It is named “USB Data Logger User SC Manual.pdf”. Issues Getting Dog-Eared? Keep your copies safe with these handy binders. REAL VALUE AT $14.95 PLUS P & P Available Aust, only. Price: $A14.95 plus $10.00 p&p per order (includes GST). Just fill in and mail the handy order form in this issue; or fax (02) 9939 2648; or call (02) 9939 3295 and quote your credit card number. 80  Silicon Chip siliconchip.com.au