CODEWITHSUNDEEP
memory-managementserial-portarduino
drinking
drinking

Reputation: 55

Arduino Serial transmitting Missing One Charcter

I am using Arduino Leonardo to transmit an string to a wifi module. The format of command that wifi module can recognize is:

AT60,1,content to a server

I am using an virtual server(TCP/IP Builder) to test the content I can received.

Here is the content I want to send:

smart/device/deviceCmd?userId=1010002003&deviceId=A00019999990002&cmd=ON

Since I try to send it again and again, I use a loop to send it. In the virtual server side, the content I got is:

smart/device/deviceCmd?userId=1010002003&devceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&devceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&dviceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&eviceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&devieId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003deviceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&dviceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&dviceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&deiceId=A00019999990002&cmd=ON smart/device/deviceCmd?userId=1010002003&dviceId=A00019999990002&cmd=ON

This is the QUESTION: There exist one terrible mistake in the content I received, which is the deviceId part never correct. It's so weird.

Here is part of related code:

//In Uart.cpp

//These three lines can sent a formatted string as "AT60,1,content"
Serial1.write("AT60,");
Serial1.write(channelID); //channel ID = 1 here
Serial1.write(reportIsFire, 76);

//In Uart.h

//Definition of the string I need to send, which has 76 characters.
char reportIsFire[76] = ",smart/device/deviceCmd?userId=1010002003&deviceId=A00019999990002&cmd=ON \n";

Here is few background of this application:

I will appreciate that If you have any idea about this question.

Upvotes: 0

Views: 307

Answers (2)

Bradford Needham
Bradford Needham

Reputation: 681

I don't have an answer, but I suspect the most likely problem is that the Wifi card can't read characters at a sustained 115200 baud rate. If possible, set the Wifi baud rate and the Arduino Serial.begin() to a lower rate, such as 57600 or 19200.

If the Arduino baud rate was simply inaccurate, I'd expect to see the problem appearing at random locations in the string, rather than about 40 characters in.

Upvotes: 0

rdtsc
rdtsc

Reputation: 1074

I am betting that the serial baud rate of the Arduino is not 100% correct. Increasing the buffer size will not matter if the data is being lost due to a timing issue in the physical link.

I'd recommend double-checking the code that initializes the serial baud rate generator. It may be possible to get a closer rate to 115,200 by either adjusting the available settings, altering the main clock speed (if possible), implementing some form of flow control, or all of the above.

In extreme cases, you may consider using a special-frequency oscillator. Many Microchip PICs use an internal or external 4MHz or 8MHz crystal, but this can produce far too much timing error for lengthy serial transmissions at high speed. In that case, something special, like a 7.3728MHz crystal can be used, bringing the accuracy to exactly 100% (at least on some PIC devices.)

Lastly, another consideration is if any pre-emptive code is running on the device, such as interrupts or timers which could inadvertently interfere with the serial output.

Upvotes: 1

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