I am using an Arduino Pro Mini 328P (3.3v, 8Mhz) with Xbee series 1. I have set the frequency to 1 Mhz and the baudrate to 9600. Also I have set baudrate to 9600 in the Xbee. I have also tested that at this baudrate Xbee is sending the data properly in a normal scenario.
Now what I have done in my project:
I have registered my Xbee with the gateway and then it will go to sleep (I have used pin hibernate mode) then it will wake up by a digital pin of the Pro Mini. I have put a delay of 19ms, after which the Xbee will try to send data. After sending the data it will go back to sleep.
The problem is that it behaves randomly when sending data to the gateway (which also has the same Xbee series1). Sometimes it sends the data perfectly, sometimes sending fails. I have also enabled RR to retry 6 times in case the Xbee fails to send the data the first time.
I have no idea how to solve this problem because of the randomness in sending the data.
I have put two Xbees nearer (I have two nodes with the same hardware and the same code). There is an interval between of around 4 minutes. So when one Xbee sends the data perfectly, after that 4 minutes gae (time difference of two RTC on different nodes) the other one fails to send the data. In this condition what can I conclude?
As a side note, the Xbee will try to send the data every hour. To calculate that hour I have to use an RTC, which seems to work fine (I am sure because I have taken the logs, the RTC never fails to generate an interrupt).
So I am wondering what could be the possible reason and how can I fix this problem (without restarting anything if it is possible then nothing will be better than that).
And I have no choice to restart my controller.
How to debug this?
A few things. If possible, increase your baud rate so you spend less time sending data to/from the XBee. If you have a limited power budget, faster baud rates save time and energy. I don't know how the UARTs work on the Arduino, so I can't say whether 115,200bps is possible with a 1MHz CPU clock.
Second, make sure you wait for the XBee to assert CTS back to the Arduino after you wake it up. Never send to the XBee unless it's "clear to send".
Third, if you use API mode, you can watch for a "Transmit Status" frame from the local XBee back to the Arduino which will let you know when the module has successfully sent the frame, and it's safe for you to put it back to sleep.
Related
I've been trying to establish serial (UART) communication between a Raspberry Pi Model B Revision 2.0 (checked the model like described on this page) and Arduino Mega 2560. I made a service on the Pi that writes to UART and then expects a message and a coworker programmed the Arduino with an echo program. While they were communicating, I had trouble receiving data, meaning that it was clustered in 8 byte pieces and I had to introduce a timeout for waiting between them (I was actually as much as available and calling select()for the next cluster but it turned to be 8bytes a cluster, except for maybe the last one. As explained in a question I found on this site, the programmer is the one to take care of the protocol and can not rely that the whole message will be ready to read at once (that is logical).
However, when I just connected Pi's TXD and RXD pins, no matter how much bytes I tried sending, it sends them in one go (I've gone up to a bit more than 256, that's more than enough for my purposes). I also have around 50 milliseconds of duration difference, measured directly from within the program, using gettimeofday() function.
So, could anybody clear things for me:
Why is this happening?
Is this difference in behaviour expected?
Is there a potential problem in either of the devices (if that can even be concluded from the given information).
Of course, any additional information is welcome, in case I forgot asking something that is deemed important.
Why is this happening?
I tried some time back communicating Arduino-Arduino and Arduino-Pi. I faced some problems with UART communication. However, you might want to keep same Baud rate on both the devices. With Pi, you might need to trigger an event if you receive data from Arduino. On the other side, if you code runs longer, then you might lose some data i.e. your Arduino code is running something else while Pi sends data over UART.
Is this difference in behaviour expected?
Yes. Arduino is a microcontroller based device while Pi is microprocessor based (runs on OS)
Is there a potential problem in either of the devices (if that can even be concluded from the given information).
I don't think there could be any hardware problem unless it is not functioning at all.
Also, because of this issues, I switched from UART communication to SPI communication. This solved my problem completely.
I have an Arduino Uno connected to a PC via USB and I am communicating via serial to a temperature sensor from PHP.
At present, the temperature sensor records a value and sends it straight down the serial connection to the PC. However, this may not be read for a long period of time. Therefore, I think this method may be inefficient.
I was thinking I could listen on the Arduino for a serial message from the PX requesting the temperature before actually checking it and sending the message back to the PC via serial, therefore becoming more efficient as its not checking the temperature every 0.1 seconds.
My Questions are as follows:
Is this actually worth doing from a code efficiency point?
Is there a better way to improve this than my suggested method?
Would these changes improve battery performance (Eg if I was using a
different communication model and not Serial and therefore might
need a batteries)
A1: Since you already have the routines to measure the temperature and then send it to the PC there should not be much coding left to do to wait for a trigger from the PC before performing the routine.
A2: There always is a 'better' way :)
A3: If your µC does not have many other tasks to perform that keep it busy you can definitely save a lot of juice by putting the µC to sleep between those short periods of activity - which you should do anyway when running off batteries.
I'm building a clock. I want to set the clock by plugging an Ethernet cable into the clock. Most of the time the clock would not be plugged into the Internet.
I have an Arduino board and an Ethernet shield that can successfully connect to a time server and read the time (See the UdpNtpClient example file under Examples > Ethernet).
The problem is that to configure the Ethernet shield, the Ethernet.begin() call blocks for 60 sec if the shield is not connected to the Internet. I would like the clock to tell the time and periodically check to see if it has an Ethernet cable plugged in, and if so, make any corrections to the time. Most of the time this check is going to have a negative result, however, so I can't have the clock freeze for 60 sec each time.
Is it is possible to detect if the cable is connected in a quicker way than the Ethernet.begin() function? Is it possible to write a "multithreading" solution, where Ethernet.begin() is non-blocking?
Looking at the stock Ethernet library, it's not possible to prevent it from blocking.
I'm guessing you're using DHCP? This appears to be where the blocking comes from. Do you get the same problem when using a static IP address?
There's a number of blog posts available on Google covering this exact issue, including some forks of the Ethernet library that would allow you to do this in a non-blocking fashion.
In the DHCP.h header file you can find the class definition for a new DHCP connection.
Then you can see that there is a default timeout value of 60000ms.
(helpful hint: if you get past the initial effort, and start using eclipse to manage your adruino projects, its really great because you can just press F3 on a functions like Ethernet.begin and take a bit of a trip through the libraries to find these types of settings)
Its difficult to know how long the timeout should be. But a minute seems like a really long time. Of course you don't want to go to short.
I wouldn't go less than 15 seconds.
/David Cox
I have the following setup. I have a hardware device connected to COM1 and COM2. In order to test it I have software simulators connected to COM1 and COM2 (RS-232 ports). These simulators receive and transmit data via my hardware device.
I need to calculate the throughput time of my hardware device. For example, if the simulator on COM1 sends a message at time A then I need to establish when it arrives at COM2, giving me Time B. The throughput is then simply B-A.
The problem I'm having is that I can't find a free serial port spy which works accurately enough for my circumstances. I've tried Sysinternals' Portmon, but it is only accurate to a second and I need to know the answer to the nearest tenth of a second. I also tried Free Serial Port Monitor, but it has inaccurate timestamping.
Any suggestions on suitable software?
Use Portmon. Change the time format; it can show the time in milliseconds (click the timer button on the tool bar - or Ctrl + T or menu Options → Clock Time).
Or use Portmon with more data you can get accurately.
I currently have an embedded device connected to a PC through a serial port. I am having trouble with receiving data on the PC. When I use my PCI serial port card I am able to receive data right away (no delays). When I use my USB-To-Serial plug or the motherboards built in serial port I have to delay reading data (40ms for 32byte packets).
The only difference I can find between the hardware is the UART. The PCI card uses a 16650 and the plug/motherboard uses a standard 16550A. The PCI card is set to interrupt at 28 bytes and the plug is set to interrupt at 14 bytes.
I am connected at 56700 Baud (if this helps).
The delay becomes the majority of the duty cycle and really increases transfer time. (10min transfer vs 1 hour transfer).
Does anyone have an explanation for why I have to use a delay with the plug/motherboard? Can anyone suggest a possible solution to minimizing or removing this delay?
Linux has an ASYNC_LOW_LATENCY flag for the serial driver that may help. Whatever driver you're using may have something similar.
However, latency shouldn't make a difference on a bulk transfer. It should add 40 ms at the very start of the transfer and that's it, which is why drivers don't worry about it in the first place. I would recommend refactoring your transfer protocol to use a sliding window protocol, with a window size of around 100 packets, if you are doing 32-byte packets at that baud rate and latency. In other words, you only want to stop transmitting if you haven't received an ACK for the packet you sent 100 packets ago.
You'll probably find that different USB-Serial converters produce different results. We've found that the FTDI ones work well for talking with embedded devices. Some converters seem to buffer the data for a long time and/or fragment it.
I've never seen a problem with a motherboard connection - not sure what is going on there! Can you change the interrupt point for the motherboard serial port?
I have a serial to usb converter. When I hook it up to my breakout box and create a loopback I am able to send / receive at close to 1Mbps without problems. The serial port sends binary data that may be translated into ascii data.
Using .Net I set my software to fire an event on every byte (ReceivedBytesThreshold=1), though that doesn't mean it will.