lwip | Light Weight Image Processor for NodeJS | Computer Vision library
kandi X-RAY | lwip Summary
kandi X-RAY | lwip Summary
This module provides comprehensive, fast, and simple image processing and manipulation capabilities. There are no external runtime dependencies, which means you don't have to install anything else on your system.
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QUESTION
I am integrating a library (lwip) and I want to reroute the logging mechanism from printf to something I wrote myself (which logs directly to my uart).
In some header file the following code exists
...ANSWER
Answered 2021-May-14 at 14:15extern "C" void logLineToUart(const char * log, ...);
You need to tell it to make the name C-linker compatible the first time it is seen.
updateThe extern "C" is only when compiling as C++. It is not legal syntax in C. You can use extern by itself (it is implied if you leave it off).
That's not very friendly... C++ accommodates sharing header files with C by accepting syntax that would not apply to C++, just to make it easy to use the same header file contents. In particular, using (void) for empty parameter lists (which is "an abomination") and allowing a comma in variadic function parameter lists ( (int x ...) is how C++ originally defined it; when the same feature got incorporated into ANSI C they used (int x, ...) with a superfluous comma that is not needed by the grammar.) C++ compilers accept both of these to make it easier to consume C headers...
But, you have to add extern "C" around everything. This introduces conditional compilation anyway, even though C++ accepts the C syntax. Note that for a single declaration, extern int foo (int); the extern is allowed and implied if you leave it out. If the C compiler allowed the linkage specification even though only "C" is available, it would make life easier. Note that in most cases, the C and C++ implementation are the same compiler suite, and often one language supports some features of the other as extensions. It would be cool if gcc etc. supported extern "C++" in C mode, since that code base certainly does know how the name encodes the parameters.
QUESTION
I'm trying to send an image from a node.js server to ESP32 chip using WIFI and ESP-IDF. I believe this transfer happens over a TCP/IP connection. I'm able to send a regular text data using a http get request or the http_perform_as_stream_reader function shown below. But when it comes to transferring an image from the node.js server, I'm unable to do so. I seem to be receiving garbage on the client side. The ultimate goal is to save the image into a spiffs file on ESP32. Here's my code:
Server side:
...ANSWER
Answered 2021-May-11 at 05:08Application should not assume that esp_http_client_read reads same number of bytes specified in the length argument. Instead, application should check the return value of this API which indicates number of bytes read by corresponding call. If the return value is zero, it indicates that complete data is read.
To work correctly, application should call esp_http_client_read in a while loop with a check for return value of esp_http_client_read.
You can also use esp_http_client_read_response, which is a helper API for esp_http_client_read to internally handle the while loop and read complete data in one go.
Please refer http_native_request example which uses esp_http_client_read_response() API.
QUESTION
I'm currently building an embedded device that uses the open source light-weight IP package (lwIP) to host a static webserver to clients using html files and http requests. lwIP is somewhat different than a normal webserver because it is bare bones and configured to serve these files through a NOSYS declaration.
In an extremely simple scenario, I'm trying to host this file (index.html):
ANSWER
Answered 2021-Apr-29 at 15:24What you have pasted are the request headers that your browser sends to the server. The problem is with the response headers that the embedded server sends back. In particular the Content-Type header isn't correct. It should look something like:
QUESTION
I am struggling (like many others it seems) to get started with LwIP over PPPos (ppp over serial) for STM32. I could have ended that sentence earlier, because even without PPPos I am having a hard time understanding where to start.
I have read, and read, and read. Their official home page, wiki, tons of forums, and trying to digest github examples for other platforms. But still I am having a hard time to have a clue where to start.
There seem to be little (none?) examples on this online taking me through the whole process. And I really don't get it. The IoT world is exploding. So I really thought it would be "easy" to have some hello world example.
What I have at the moment:
- An LTE modem which I can use via AT commands
- A small application which runs on my nucleo (F446ze) board which can blink LEDs, communicate over UART3 with my PC, and UART2 with the LTE modem
- Played around with free RTOS, that part was surprisingly easy to familiarize
But instead of clumsy internet communication using AT commands (and AT+CMQTT commands) I want to rely on a proper TCP/IP stack. Set the LTE modem in data mode (PPP), and have LwIP take over the TCP/IP stack.
Is this still very complicated anno 2021? Or am I completely looking in the wrong direction? Is there anybody who can point me in the right direction?
I already have freertos working too. I don't mind to use it. I also don't mind to go without. I am just looking for a way to get started with LwIP without having to reverse engineer the LwIP stack completely.
...ANSWER
Answered 2021-Apr-11 at 21:34Going top-to-bottom, you have your application code which in the end will likely want to talk to some server: resolve DNS name, open a tcp connection etc. This is what LwIP provides - a set of API functions: socket functions, DNS functions and other. For example, when you do a TCP socket connect to a given IP address and port, it decides which out of available network interfaces to use, constructs a frame in form of array of bytes and sends those bytes over that interface. This is where LwIP part ends - it requesting given network interface to output X bytes it provides, as well as consuming any bytes that may arrive on that interface. It doesn't know how exactly to make the bytes "come out", but it knows how to construct the data to send and understands the data you give it.
Going bottom-to-top, you have your modem - LTE, 3G, 2G, doesn't really matter. Modems provide a set of AT commands to talk to them to perform a set of functions: set SIM card PIN, get signal quality, list available operators, select an operator etc., as well as a way to switch it to PPP mode, which also done ATD command. Assuming the modem has been configured properly before, once you switch it to PPP mode it'll be able to send data using PPP protocol and will also "spit out" any data it receives. This is where the modem part ends - when switched to PPP mode, the modem is able to send and receive raw network traffic using PPP protocol. It knows how to output the raw bytes you give it, but it doesn't understand them on a very high level.
Your role is to connect (interface) both parts. Your modem uses PPP to produce and consume network traffic. LwIP has the capability to understand and produce PPP frames.
In case of sending data out, after preparing a PPP frame LwIP is going to call the sio_write function that is expected to send provided bytes to modem that's already in PPP mode. This is the part that you need to fill in. In case of reads sio_read is used and it's your job to fill it in so that it returns bytes that were received from the modem. How you're going to do that - using RTOS and queues for bytes, no RTOS or any other way - doesn't matter. It's what you find more convenient or what fits your overall project structure better. As long as those functions do what they're supposed to, LwIP will be happy to use them.
This interfacing is discussed in more detail here: https://lwip.fandom.com/wiki/PPP#PPP_over_serial. Again, the general concept is that LwIP is just a software library and in the end it'll want to send and receive bytes. Your job is enabling it to do so, by filling in the functions it expects.
QUESTION
I am using TMS570LS3137 (DP84640 Phy). Trying to program UPD(unicast) using lwip to send 2MB of data. As of now i can send upto 63kb of data. How to send 2MB of data at a time. UDP support upto 63kb of transmission only, but in this link https://stackoverflow.com/questions/32512345/how-to-send-udp-packets-of-size-greater-than-64-kb#:~:text=So%20it's%20not%20possible%20to,it%20up%20into%20multiple%20datagrams. They have mentioned as "If you need to send larger messages, you need to break it up into multiple datagrams.", how to proceed with this?
...ANSWER
Answered 2021-Mar-09 at 11:31Since UDP uses IP, you're limited to the maximum IP packet size of 64 KiB generally, even with fragmentation. So, the hard limit for any UDP payload is 65,535 - 28 = 65,507 bytes.
I need to either
- chunk your data into multiple datagrams. Since datagrams may arrive out of sending order or even get lost, this requires some kind of protocol or header. That could be as simple as four bytes at the beginning to define the buffer offset the data goes to, or a datagram sequence number. While you're at it, you won't want to rely on fragmentation but, depending on the scenario, use either the maximum UDP payload size over plain Ethernet (1500 bytes MTU - 20 bytes IP header - 8 bytes UDP header = 1472 bytes), or a sane maximum that should work all the time (e.g. 1432 bytes).
- use TCP which can transport arbitrarily sized data and does all the work for you.
QUESTION
I am trying to implement a VPN service on Android. I am provided raw IP packets (TUN interface which works on layer-3) and not sure how I am supposed to send the packets. I know I can parse the IP packets to pull out the transport layer data (TCP or UDP) and then send it, but I was hoping there was a way I can just simply send the whole IP packet.
Initially, I tried using a raw socket (https://man7.org/linux/man-pages/man7/raw.7.html) and send it that way but learned that this was not possible due to permission issues. To open a raw socket you need root permissions and Android applications cannot run as root.
I found a project called LWIP (https://www.nongnu.org/lwip/2_1_x/index.html) which says that it is a TCP/IP stack implementation library, but after reading the documentation, I can't figure out how to do this.
LWIP has their raw APIs (https://www.nongnu.org/lwip/2_1_x/raw_8h.html#a17edd059f34f45a770fe2fa458ecf4dd) which looks promising but I am not sure if this is what I need. Basically, I just need a way to send the raw IP packet and then get the response, and write it back to the TUN interface -- essentially a pass-through proxy.
Any help would be greatly appreciated. Thanks!
...ANSWER
Answered 2021-Mar-08 at 06:20You're trying to reinvent the wheel. There are several appropriate encapsulation methods like GRE or IP-in-IP.
Sending a raw IP packet requires the use of an IP protocol number in any case, so your receiver can get the packets after registering that number.
For starters, it might be easier to use UDP encapsulation.
QUESTION
I'm attempting to configure a number of connected ESP32 stations via a single ESP32 AP. The easiest way for me to do this would be to send a single broadcast UDP packet to 255.255.255.255. However, my stations which are listening with an open UDP port are not receiving broadcast data at all. Is there something else I need to configure on the station/AP for this to be possible?
I've done a bit of reading and it seems like lwip/opt.h may have been prohibiting detecting broadcast packets, but after setting IP_SOF_BROADCAST and IP_SOF_BROADCAST_RECV I've seen no difference.
Here's my current station UDP listening task:
...ANSWER
Answered 2021-Feb-09 at 13:25Looks like your listening socket is missing the SO_BROADCAST option. You need something like this after creating the socket:
QUESTION
I am trying to do TCP connection between two stm32 device. Firstly everything is perfect between the line we see on the wireshark.When the TCP client reset and try to send new data, wireshark shows me Retransmittion TCP message but when I debug the server side, server side get the message and send echo message after client receive this echo message.
Why the retransmition message shows, althoug I get and send message to other side ?
FULL client code: https://paste.ubuntu.com/p/VJHzgv29FM/
FULL server code : https://paste.ubuntu.com/p/Wm9gvkSfF7/
...ANSWER
Answered 2021-Feb-01 at 08:19When using wireshark to analyze network stream, here is a doc from wireshark that can help you understand what these words means.
We can see the following thing:
TCP Retransmission
Set when all of the following are true:
This is not a keepalive packet.
In the forward direction, the segment length is greater than zero or the SYN or FIN flag is set.
The next expected sequence number is greater than the current sequence number.
For your circumstance, the problem is that the segment length is greater than zero or the SYN or FIN flag is set. This is caused by your reset, so this doesn't mean that your TCP connection causes retransmission.
QUESTION
Hello I am trying to build a FreeRTOS application for a Beaglebone black target which has a AM335X ARM Cortex-A8 processor. I am running windows but i am using a virtual machine that runs linux debian 10 which is what i am cross compiling from. uname -a provides:
ANSWER
Answered 2021-Jan-03 at 16:48set(CMAKE_C_COMPILER "/path/to/your/c/compiler/executable")
set(CMAKE_CXX_COMPILER "/path/to/your/cpp/compiler/executable")
QUESTION
I'm playing around with a ZYNQ7 (Dual-Core ARM) with a FPGA. The FPGA design has a 32-bit counter accessing the DDR via a DMA controller in chunks of 256-packets.
In the C-Code for the processor 1, I run a LWIP application to connect via ethernet to my pc. There I allocate ram memory for the DMA transactions. The address of the pointer is passed via shared memory to the 2nd Core.
...ANSWER
Answered 2020-Dec-11 at 07:58I found a solution....
I had to flush the Cache after allocating the memory, before passing the address to the 2nd Core for processing.
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