I'm just starting to learn FreeRTOS and have set up the Posix/Linux simulator on my laptop. The Blinky demo works fine but the Full demo breaks after around 5000 ticks with the error Error: StreamBuffer - tick count 50000. The Demo file produces a trace dump when you exit the application but so far as I can see it is completely unreadable. It appears as seemingly random text characters as if I have the wrong encoding or an incorrect baud rate (if I was using a physical device). I can only assume that the dump files are not supposed to be viewed as a normal text file but I cannot find this in the documentation.
Thanks in advance
That is almost certainly a false positive error that will be due to running so many self monitoring tests at the same time - some of which assume one or more of their test tasks is the only task running at the highest priority. The trace comes from the Percepio tool, see https://www.freertos.org/trace
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I am working on a block with gnuradio. I have come across a strange performance improvement when i was printing out some huge data on to terminal and the performance degrades without giving a print statement on to terminal.
I infer that while printing out to terminal i am giving gnuradio block an extra processing time for the block to process. This is just my hunch and might not be the exact reason. Kindly correct if this is not correct.
So, is there a way to add a specific amount of processing delay within a block(as what i got during printing out data to terminal) in gnuradio.
Thanks in advance
First of all, the obvious: don't print large amounts of data to a terminal. Terminals aren't meant for that, and your CPU will pretty quickly be the limiting factor, as it tries to render all the text.
I infer that while printing out to terminal i am giving gnuradio block an extra processing time for the block to process. This is just my hunch and might not be the exact reason. Kindly correct if this is not correct.
Printing to terminal is an IO thing to do. That means that the program handling the data (typically, the linux kernel might be handling the PTY data, or it might be directly handed off to the process of your terminal emulator) will set a limit on how it accepts data from the program printing.
Your GNU Radio block's work function is simply blocked, because the resources you're trying to use are limited.
So, can i add a specific amount of processing delay within a block(as what i got during printing out data to terminal) in gnuradio.
Yes, but it doesn't help in any way here.
You're IO bound. Do something that is not printing to terminal – makes a lot of sense, because you can't read that fast, anyway.
I am writing a small utility that will get the hardware and software time and print in a file.
This is to check whether both are in sync. I am searching for a vxworks function that prints the hardware time along with milliseconds.
Thanks
I looked this one up for you in the VxWorks 7.0 Manual.
try clock() - if this doesn't work (not able to test it) search the manual for terms like 'Time' and 'Clock' - yielded good results to me.
having trouble understanding the exact role of an interpreter. to quote wikipedia - "Programs in interpreted languages[1] are not translated into machine code however, although their interpreter (which may be seen as an executor or processor) typically consists of directly executable machine code (generated from assembly and/or high level language source code)."
my doubt is about this statement - "interpreter (which may be seen as an executor or processor) typically consists of directly executable machine code" ? what does that mean? interpreter is supposed to be a program .How can it 'execute' code by itself ? they have re-stated this fact by saying " interpreter is different from language translators like compilers". Can anyone clarify please ? Also what is the difference (if any) between interpreted language and machine code ?
Compiler:
Transforms your code into binary machine code which can be directly executed by the CPU. Example: C, Fortran
Interpreter:
Is a program that executes the code written by the programmer without an additional step of transformation. Example: Bash scripts, Formulas in Excel
Actually it is not that easy any more. There are many concepts between these two pols. Java is compiled into an intermediate language that is then interpreted, just-in-time compilers compile small parts of interpreted code to speed them up.
"How can it 'execute' code by itself?" Take the Excel example. If you type a calculation into a cell, Excel somehow executes the code, right? But Excel does not compile the code and run it, but it parses it and executes in a general way. Excel has a sum function that in the end is executed on the processor as an add machine command, but there is a lot to do for Excel in between.
I will briefly describe an emulator to explain the main concept mentioned in the question.
Suppose I am using Mame, a video game emulator, and select the old classic arcade "Miss PacMan". Looking at the schematic or looking directly at a PCB inside an arcade video game, it is easy to find the processor : the zilog Z80, the only large chip with 40 pins. Now, if we get the technical data for that processor, we can find the binary encoding for each instruction it can execute. Basically, it get a 8-bit data (value ranging from 0 to 255) which tells the processor what to do. In the case of the emulator, it read the byte (the exact same bytes as would do the Z80 processor inside the original miss pac-man electronic board), determine what a Z80 would do and simulate the instruction.
Some classic video game may have use a x86 processor, similar to the one currently used in most PC. Even when selecting such a game in Mame, the emulator would still read the bytes as found in that game and interpret each one the way the x86 processor would do. In other words, the emulator would not take advantage of the fact that the PC and the emulated game are using a similar processor. It would perform the same steps to emulate any game no matter if the PC on which Mame is running share any similitude with the original game.
You are asking how an interpreter could execute code? The interpreter is a program (the interpreter is just a software, not a physical processor). The wording is effectively confusing. For this sentence to make sense, we would need all the following conditions:
1 - the program to interpret is already in binary, in a machine language that can be executed directly by the processor used in your PC
2 - the program location, the exact address used, is the same as the location that you can reserve in your PC
3 - any library and any I/O occupy the exact same address
When all these condition can be meet, the interpreter could just tell the processor on your PC to stop executing the code from the interpreter but instead, "jump" in the code of the program to be interpreted. Anyone could then say : it is not an interpreter, it is just a launcher.
Maybe such an interpreter which actually does not interpret but let your processor do the real job is still useful in the following way: it could let your processor perform some of the work, but request the generation of an exception when the code to be interpreted is executing some type of instruction. For example, let the code running, but generate a "general protection error" or "trap" or "exception" when trying to execute any of the variant of "IN" or "OUT". The interpreter would take note of the I/O port being written or it would choose a value to give instead of allowing to read a real I/O port. The interpreter would then manage to get the processor "jump" in the program to interpret at the location just after the instruction "IN" or "OUT".
Normally, an interpreter read an ASCII text file, the original source code (which could be Unicode instead of ASCII), determine line by line, word by word, what a compiler would do, then simulate the task on the fly. When the original compiler would need to read many lines to fully understand the current task, the interpreter would also need to read all these lines before being able to simulate the same task.
A big advantage of an interpreter is that it can not crash. Because every instruction is simulated, it is not sensitive to any bug or malicious code. That was a big advantage at the time when computers needed to reboot after encountering any bug, at a time where reboot was taking 10 minutes or more.
Today, with fast SSD to reboot in 5 second and with reliable operating systems which can trap any error in one process and close that process without affecting the stability of the machine, there is less incentive to prefer a slow interpreter over a much faster JIT or much much faster binary executable
I'm porting u-boot-2013.10 to MPC8306 based board. Previously, I can erase the first several sectors of Nor Flash using BDI2000. But after sometime, when the porting task is nearly done, (I mean that I can use gdb to trace the code execution and find the u-boot code runs into command line mainloop, though there are no serial output at the time, due to error configure of Serial Port)the first 256KB of Nor Flash can't be erased even if after power off reset. Other sectors can be erased normally.
The Nor Flash is Micron M29W256GL, with block size 128KB. I'm sure the WP# Pin has been pulled high, so there is no hardware protection upon the first block.
When config the jumper on board to change the PowerPC Config Word in order not to let MPC8306 fetch boot code at power up, the problem remains.
I used to run u-boot-1.1.6 on this board, I have erased this version of u-boot so many times without the problem mentioned above. I guess u-boot-2013.10 made some new approach to flash manipulation or others, for example, non-volatile protection on first 256KB of flash.
Is there someone can help me to solve the problem? I would very much appreciate your help.
I recently I came across an error that I cannot understand. The game I'm developing using Cocos2D just freezes at a certain random point -- it gets a SIGSTOP -- and I cannot find the reason. What tool can I use (and how do I use it) to find out where the error occurs and what's causing it?
Jeremy's suggestion to stop in the debugger is a good one.
There's a really quick way to investigate a freeze (or any performance issue), especially when it's not easy to reproduce. You have to have a terminal handy (so you'll need to be running in the iOS simulator or on Mac OS X, not on an iOS device).
When the hang occurs pop over to a terminal and run:
sample YourProgramName
(If there are spaces in your program name wrap that in quotes like sample "My Awesome Game".) The output of sample is a log showing where your program is spending time, and if your program is actually hung, it will be pretty obvious which functions are stuck.
I disagree with Aaron Golden's answer above as running on a device is extremely useful in order to have a real-case scenario of where the app freezes. The simulator has more memory and does not reproduce the hardware of the device in an accurate way (for example, the frame rate is in certain cases lower).
"Obviously", you need to connect your device (with a developer profile) on Xcode and look at the console terminal to look for traces that user #AaronGolden suggested.
If those are not enough you might want to enable a general exception breakpoint in Xcode to capture more of the stacktrace messages.
When I started learning Cocos2D my app often frooze. This is a list of common causes:
I wasn't using sprite sheets and hence the frame rate was dropping drammatically
I was using too much memory (too many high-definition sprites. Have a look at TexturePacker and use pvr.ccz or pvr.gz format; it cuts memory allocation in half)
Use instruments to profile your app for memory warnings (for example, look at allocation instruments and look for memory warnings).