SparkFun Forums

[nsornin]

Dear all.
I am trying to use Serial1 on pins D9/10 on my Artemis nano board to talk to a sensor and i have some very strange behavior.

If i try :

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#define BAUD 115200       // any number, common choices: 9600, 115200, 230400, 921600
#define CONFIG SERIAL_8N1 // a config value from HardwareSerial.h (defaults to SERIAL_8N1)


void setup() {
    Serial.begin(BAUD); 
    Serial1.begin(9600); // set the baud rate with the begin() method
}

void loop() {
  Serial.printf("this print on Serial\n");
  Serial1.printf("this on Serial1\n");
  delay(1000);
}

Then both prints are sent both on physical pin D9 and on the USB console at 9600 bauds. I am using a scope to capture pin D9 and i see both messages concatenated on that pin.

If i now invert the order of initialization of serial ports:

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void setup() {
    Serial1.begin(9600); // set the baud rate with the begin() method
    Serial.begin(BAUD); 
}

both prints are sent to pin D9 and USB console (i get both messages on both UARTS again) , but this time at 115200 bauds (on both UARTS)

So it seems that changing baudRate on Serial1 changes Serial and reciprocally. More intriguing , why can is see the output of Serial.printf on the pin D9 using my scope ? How can the ouput of the the Serial.printf command be on two physically separated UART TX pins ?

How do i decouple Serial (which should only be talking to the USB bridge) and Serial1 which should be a hardware UART connected to pins D9/D10 ?
Thank you so much for any clarity you can bring. I purchased that board specifically because i has 2 UARTS (on top of BLE off course ) , so i am kind of stuck there

[paulvha]

I have tried this on my ATP (do not have a Nano) and can not reproduce it. In the many projects with different Artemis boards (Edge, ATP, Micromod etc) never had this problem. I check the Nano pins for Serial and Serial1 and they are differently assigned. Looks to me like a corrupt board library. Try reinstalling the Artemis 2.2.1 library and see what happens

[nsornin]

Thank you so much for your answer Paul. I will try to reinstal the lib and recheck. Will keep you posted

[paulvha]

Given that someone else also complained about Serial speed setting I have bought an Artemis Nano.
Compiled your example and .... now I got the same problem as you. I could not set the speed for Serial and Serial1 independent from each other and the data is showing up BOTH on Serial as well as Serial1.

I have been able to find the root cause and solution.

An Apollo3 chip has 2 uarts : UART0 and UART1. When a Serial instance is created, based on the provided TX and RX pad, a lookup is performed to decide which UART to use.

First, the Serial-instance is created (TX = 48 / RX= 49) and based on the lookup UART0 is assigned. Then the Serial1-instance is created (TX=39, RX =40), but now DUE TO AN ERROR IN THE LOOKUP TABLE, it is ALSO assigned to UART0.

In the same lookup table (PeripheralPins.c) there are already entries to assign (TX=39, RX =40) to UART1. So I commented-out the 2 lines that enable UART0 assigment. Serial1 is now assigned to UART1 and it now works as expected.

The change requires a new Artemis-Nano pre-build archive for Mbed, which I have created.

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Go to  the directory :

Windows :  <userdir>\AppData\Local\Arduino15\packages\Sparkfun\hardware\apollo3\2.2.1\variants\SFE_ARTEMIS_NANO\mbed

Ubuntu/Linux:~/.arduino15/packages/SparkFun/hardware/apollo3/2.2.1/variants/SFE_ARTEMIS_NANO/mbed

There is the archive file called libmbed-os.a.
If you want you can make a safety rename or copy.

Now UNZIP the attached  libmbed-os.zip in this folder to get a updated  an libmbed-os.a and recompile your sketch .
 All should be working now.

Note 1: Why I did not see this on any of the other boards ? Because they use TX=24 / RX=25 for Serial1, which in the table can only be assigned to UART1.

Note 2: I have made a github bug report : https://github.com/sparkfun/Arduino_Apollo3/issues/474

[dykesc]

Could this explain why, after defining my SDA and SCL as D10/D9 in the Apollo 3 I2C example, my INA219 sensor is detected when it is wired to Nano pins 6/7?

[paulvha]

no, but I will answer this on your original post not to mix topics.

[dykesc]

Thanks