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Serial Communication (USART)

(4 posts) (2 voices)

Started 3 years ago by
Latest reply from drinkdhmo

Anonymous
Unregistered

Hi all,

Very weird problem! Trying to connect OpenLog with Maple-Mini to record some accelerometer data. The accelerometer is connected via I2C1 and works beautifully (BMA180). OpenLog has been a bit of an issue. I am able to receive incoming bytes (eg the powerup '12<') from the OpenLog to the RX pin but not able to write to it via the TX pin.

To try and debug, I isolated the TX line (from Serial3) to see if anything was going out. Connecting to an oscilloscope showed that Serial3.print or Serial3.write was not producing any output on the TX line. Connecting it to the RX pin on Serial1 confirmed that nothing was coming out of the TX lines. Since I know that the RX pin is not damaged (I have used it before) and the Serial3 RX and TX pins are not damaged (as I have used them for I2C2 before), why is Serial3 not sending anything? Can someone please help???!!

Kind regards,
Sumeet

Posted 3 years ago #
drinkdhmo
Member

Without anymore specifics, I would suggest checking the basics:

Make sure you call Serial3.begin([baud rate]);

Make sure you don't reassign the respective pins later with a call to pinMode();

You could also look to see if there is a Timer conflict (I don't remember if the serial ports consume one of the internal timers).

Maybe post your code somewhere and we can look closer.

Posted 3 years ago #
Anonymous
Unregistered

Nope Serial3.begin(baud) were done.

Righto I got it working but only after I tried this debug in the setup() function:

SerialUSB.print("RX pin is: "); SerialUSB.println(Serial3.rxPin());
SerialUSB.print("TX pin is: "); SerialUSB.println(Serial3.txPin());
The numbers it printed corresponded to the pin numbers from the Maple board - not the maple-mini. I then went into the board.h file for both the Maple and Maple-mini. Both header files had the correct #defines in there for there respective board. However, inspite of the fact that I used the following commands during compile:

cp <filename>.cpp main.cpp
export BOARD=maple_mini
BOARD=maple_mini make
BOARD=maple_mini make install

It still for some reason, referenced the maple board.h file instead of the maple-mini. So I deliberately went in and changed the constants in the maple board.h file to be the same as maple-mini and it all worked! While the fix is fine, I am still uneasy about having to do this fudging of numbers. Why did the compiler not automatically use the maple-mini board.h file?

Any thoughts?

Posted 3 years ago #
drinkdhmo
Member

Check your Makefile. In my project I ended up just hard coding the target board so that it couldn't get confused. My makefile reads as follows:

.
.
.
# Try "make help" for more information on BOARD and MEMORY_TARGET;
# these default to a Maple Flash build.
BOARD ?= maple_mini
MEMORY_TARGET ?= flash
.
.
.

Just for curiosity's sake, before you modify your Makefile try "echo $BOARD" after compiling to see if your Makefile overwrites the environment variable.

Posted 3 years ago #

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