Hello my serial monitor font is get trouble, i can't fix it, anybody knows ?
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Either the sending device is sending non-sense or non-ASCII data or (more likely) you have a baud rate mismatch.
The serial interface you're using here is asynchronous. That means there is no common clock to synchronize communication. Hence the receiving side must know the baud rate of the sender or vice versa. If you're sampling the Rx line with the wrong frequency you don't recieve what has been sent but more or less random characters.
Alter the baud rate setting until you read the correct data.
Give this a read
https://learn.sparkfun.com/tutorials/serial-communication/all it explains serial communication for beginners.
Related
I am trying to read BLE telegrams sent to a usb plugged reciever to my PC.
I am using a serial port reader ( used putty at first then tryed some other software from the net). However, I get nothing, not data at all sent; not from my sender not even any telegram from may be other unknowm devices that may be there advertising.
I have run mode on command line to give me information and it shows that my com port has a baudrate of 1200.
I must say this value was not fix it goes from 1200 to 57600.
I know that my data is sent at a baudrate of 57600: so I'm thinking may be the problem is that the baudrates being different it can't get the data but then it should come to a time where I can see at least some insignificant data of incomplete telegram. I have also tried to change the baudrate on the serial com port reader but same result nothing at all.
My question is what might be the problem and how can I fix it ? in other words having a BLE reciever and tranciever how can I read the telegrams on COM ports
Please feel free to slap me and send a link if this question has already been answered; I just couldn't find it. I did search though.
I've been trouble-shooting communication with a serial device. In looking over lots of documentation, I now understand what the settings for "baud rate," "data bits," "stop bit," and "parity" mean. But what I can't seem to understand is who (sender or receiver) determines these settings.
Say I have a serial device plugged into my computer. In my code, I open a connection to the serial port and specify something like 9600,8,E,1. When I specify these settings, do these get sent to the sending itself, so that it knows how to send the data to my receiver? Or is it more common for a sender to expect a receiver to comply with strict settings?
The issue I'm having is that I attempted to use "Even" parity, and that resulted in tons of irregular transfer errors. When I use "Odd" parity, however, those errors go away. There is also a USB to Serial adapter involved in my set up. There aren't any transfer errors with Even or Odd parity without the adapter in the middle. So I'm just having a hard time understanding whether the device itself doesn't support sending with Even parity, or whether the adapter is the thing causing trouble, etc.
Thanks.
When I specify these settings, do these get sent to the sending itself, so that it knows how to send the data to my receiver?
No.
To expand on the comment by Hans Passant, both sides of the serial port have to agree on the settings, otherwise they won't talk to each other. If they don't agree, you will get gibberish data on either side as the hardware will read the data at an incorrect time. The settings are normally documented in the manual for the device that you are attempting to communicate with. For example, to communicate with a Cisco router, you will generally use the following settings:
Bits per sec : 9600
Data bits : 8
Parity : none
Stop bits : 1
Flow control : none
When you setup the serial port on your side, you must use these same settings, there is no hardware-level handshake between the two devices that determines the speed that they will communicate at.
Sometimes, the format for the serial port settings may be given in a format like the following:
9600,8,N,1
Which is just shorthand for the above quote(9600 baud, 8 data bits, no parity, 1 stop bit)
In my experience, most devices default to 9600,8,N,1, the next common serial setting is 115200,8,N,1
I am trying to connect a joystick to my pc. The device has a serial cable which is supposed to be inserted into another device (a steering wheel), but instead I want to use it directly. Eventually I plan to connect it to a program that am currently writing.
How can I communicate with this device? I know how to communicate to a serial device, I just don't understand what I should send and expect to receive.
Debugging attempts:
If I connect it directly to my PC's serial device and using a program such as moserial I can sort of communicate with it, if I pound on the keyboard it returns (usually) one byte and "=\n" per byte sent. The return codes do not seem to always correspond to the state of the joysitck. It seems to be returning the same value for the same value. Once or twice I noticed that if I send a large amount of random data I can get it to hang until I switch the position of the joystick. But for the most part there seems to be nonsensical responses (same input per output regardless of state). I also tried a serial-to-usb converter which had a different result. Under USB the device does pretty much nothing regardless of the baud rate. I have noticed that if I send an incredible amount of random kepresses I occasionally get a single unprintable character in response.
I was expecting to get a continuous stream of numbers corresponding to the state of the joystick.
Summary:
I don't know if my direct serial connection is just showing noise, I did try a second serial to USB converter which had the same results. Any ideas or suggesting in determining how to communicate with this device?
I'm building a project that uses an HID OEM75 as the access point for a locking mechanism. We're doing our control through an Arduino Duemilanove (ATmega328). We're working with SPI for the security and (apparently) support. (I realize that any RFID chip has pretty weak security.)
I'm currently struggling with receiving bytes via SPI from the card reader.
The card reader is in autonomous read mode, meaning it reads a card, sends a signal to the Arduino (via a card present line, separate from SPI), which tells the Arduino to pull the Slave Select line high to activate the transfer cycle from the card reader. This is where I run into trouble, I can't understand how I can get the Arduino to simply read the bytes coming in from the card reader without sending any command bytes to the card reader?
The default command structure, SPI.transfer(0x00), sends a byte (in this case the dummy byte 0x00) and then accepts a byte from the source, but because our source is operating autonomously, it won't accept the dummy byte (and that will actually mess up its operation).
To word it simply: how can we accept a string of bytes from the slave source without sending bytes from the Master Source, using Arduino's SPI library?
If I am not wrong, using the SPI bus as a master is like shifting a dummy byte to the slave while reading the incoming byte in reverse.
USB HID Host driver for Windows from embedded24.net
Well it's a little late, but hey, it'll help someone out there.
First off:
which tells the Arduino to pull the Slave Select line high to activate
the transfer cycle from the card reader.
This is SPI, you pull the Slave Select low to activate the slave, not high. You put it high to tell it to shut up while others are talking.
I can't understand how I can get the Arduino to simply read the bytes
coming in from the card reader without sending any command bytes to
the card reader?
That's because you don't. In SPI, the master (which the arduino is set up as and the SPI.h library assumes) initiates communication. It sends out data on the MOSI line and the slave responds on the MISO line. If you have nothing to say to the slave, just send 0xFF or whatever dummy bytes and then check what came in on the MISO. On the arduino, I believe that gets stored in the SPDR, SPI data register. Or use whatever the spi library gives you.
but because our source is operating autonomously, it won't accept the
dummy byte (and that will actually mess up its operation).
If the case is that you really can't send data to the SPI slave device without it screwing up, then it's not actually implementing SPI, and the arduino SPI library won't help you. You'll have to hack out your own solution. The SPI standard is actually pretty loose and all sorts of people do it their own special way. Which is vastly annoying. I've seen devices use the SS line to initiate clock synching. Which means you can't just tie it to ground to have that slave always be on.
Before you write it off though, I'd suggest investigating why it won't accept the dummy byte. You might be using "3-wire" SPI which combine MOSI and MISO and turn it from full duplex into half duplex, and you'll have to get the timing right so you don't trample everything.
When getting into the nitty gritty of SPI, an oscilloscope works wonders for seeing what actually happened vs what you think should have happened.
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.