Mpu9250 and qduino - code is not working

Hi there, I have some problem with the code at the moment. So what i want to do is to make the qduino read the code and display the inclination value. I am trying to measure the inclination angle.


#include <Qduino.h>

#include <MPU9250.h>

// an MPU9250 object with the MPU-9250 sensor on I2C bus 0 with address 0x68
MPU9250 IMU(Wire,0x68);
int status;
float ax0 = 0 ;
float ay0 = 0 ;
float az0 = 0 ;

void setup() {
// serial to display data
while(!Serial) {}

// start communication with IMU
status = IMU.begin();
if (status < 0) {
Serial.println(“IMU initialization unsuccessful”);
Serial.println(“Check IMU wiring or try cycling power”);
Serial.print("Status: ");
while(1) {}
ax0 = IMU.getAccelX_mss();
ay0 = IMU.getAccelY_mss();
az0 = IMU.getAccelZ_mss();

void loop() {
// read the sensor
float ax = IMU.getAccelX_mss();
float ay = IMU.getAccelY_mss();
float az = IMU.getAccelZ_mss();
//float inclination=180.0acos(az/sqrt(axax+ayay+azaz))/M_PI;.
float inclination = 180.0acos( (ax0ax + ay0ay + az0az)/sqrt( (axax + ayay + azaz)(ax0ax0 + ay0ay0 + az0*az0)))/M_PI;
Serial.println (inclination);

but When I ran this code on arduino uno it worked perfectly fine, however, when I tried to run it on qduino, the serial monitor says:

23:38:13.187 -> IMU initialization unsuccessful

23:38:13.187 -> Check IMU wiring or try cycling power

23:38:13.187 -> Status: -1

But it runs well with arduino uno so i do not know what the problem is. The circuit is the same which looks like this.

can anyone tell me what the problem is? thank you in advance.

Might not be of any help. But …
Have looked at Sparkfun schematic and library on Github. Dont know which MPU9250 library you are using, so I chose the first one in the list, Bolder Flight systems. The begin routine first intialises the SPI or I2C interfaces depending on which you are using. Then there is a whole lot of if statements that return negative which is where your code is dropping out. If you check these values it might give you a clue. But …

UNO Qdino differences, 16Hz clock 8MHz clock, Atmega328P Atmega32u4.

Anyway, hope you get it resolved, cheers

EDIT: Further investigation. Status return of -1 (as you have shown) is first read / write to the MPU9250. It writes a value then reads it back, if it is not the same it returns with an error. The register is the clock source to the gyro. I ran the code on a UNO (dont have Qduino or MPU9520) status returned is -1. Which it would be as there is no device connected to the I2C bus.
From this I conclude the I2C interface is not working in your set up and may be due to the CPU clock difference.

Hey James and Jinky,

Yes, that’s almost definitely the issue here (the incompatibility or continuity issues with the I2C comms) the best way I can think of to prove that is to use the Qduino with another I2C device to see whether you can replicate the issues, try another script that depends on I2C comms with that board to see whether the issue appears there as well, and try another script with a different device connected to the Qduino to see whether there could be issues with the I2C connections to the board itself. Otherwise, even something as simple as using another microcontroller to see whether the same issue occurs could provide some useful info. The script looks good, so I imagine that won’t be causing any issues here. Please let us know if you solve the issues, the solution could be useful for future users of that board.

Core Electronics | Support


Which is a little different to the sparkfun’s model.

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Hey Jinky,

Yes, they’re different, the standards used will be quite similar, and they should both be compatible with that microcontroller from the specs.

Core Electronics | Support

I believe that they both use the 9250 chip, so code should drive both boards without change. The Sparkfun tutorial should be a good starting point. There is also a link in the tutorial to more information on the algorithms used.

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Reference to Sparkfun was to the Qduino not the MPU9250. I should have been more clear.
The following is from the Atmega328P datasheet.

You can see the CPU clock is tied in with the generation of the SCL clock. The original problem is that the MPU9250 does not work with the Qduino but does with a UNO. One is 8MHz the other 16MHz. It would be my starting point.
The library might not be setting the right values. Happy to look at it if you let me know which you are using.


Thanks @James46717

My reply was aimed at @Jinkyung128517 specifically.

Also for @Jinkyung128517, the Arduino Uno is a 5V device, and the qduino is a 3.3V device. You may need a level shifter with the qduino to get appropriate voltage levels to drive the 9250 successfully.

Search for level shifter in the Core store to find something suitable.

Have not found any reason why the MPU-9250 library should not work with both UNO and Qduino I2C interface.
When using the Arduino IDE you select the board you wish to program. When the program is compiled it accesses a text file related to the board you have selected and sets a number of environmental parameters. One of these is F_CPU, which is then used to set the correct clock frequency.
Serial.println(F_CPU); Will show what clock it is set to, UNO = 16000000, Qduino = 8000000.
The I2C library is set up using F_CPU.

This setting of the correct clock rate has got me a number of times in my projects.

Anyway, just an idea, hope you get it to work, cheers

Hi thanks James, I am currenctly using this library:
I am a design student with just basic knowledge with these electronics and coding so it takes a while (some language i don’t quite understand) to fully understand these maths and etc. Thank you for your consideration and if you could explain in simple terms after looking at the library it will be great. I will follow procedures according to you feedback.

for qduino i installed

(port isn’t showing becuase i haven’t connected to it. also I have tried adding “#include <Qduino.h>”

into the comments, it didn’t work.

Hi @Jinkyung128517.

As @Robin57159 mentions you probably should check what voltage you are running on the MPU9250. Your circuit diagram shows it connected to 3.3V on the Arduino and that’s what you want when connecting to the Qduino. The MPU9250 is designed to run at 3.3V and the DOF board has a built in regulator to drop a 5V supply voltage to 3.3V. When connecting the MPU9250 directly to 3.3V you should bridge the jumper near the voltage regulator with some solder so that the voltage regular is bypassed.

Next, check the I2C wiring. The Qduino I2C bus is on pins D2 (SDA) and D3 (SCL). Check that you are connecting to these pins and swap these connections just in case the SDA and SCL signals are the wrong way around.

It might also be possible that you need the Wire library in order to get I2C to work on the Qduino. Try adding #include <Wire.h> to the top of your sketch.

If none of that works try Bryce’s suggestion and connect a different I2C sensor (eg MPU6050) to the Qduino to see if that works.

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Thanks @Scott96306 , I didn’t know it had different SDA SCL pin areas for Qduino Thank you, It is working now! I also have problems detecting the correct angles as I mentioned in the email and I also posted up on this forum: Mpu9250 inclination detecting code - need help in defining the default value

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Sorry I have sent the wrong site address, this is the correct one. Mpu9250 inclination detecting code - need help in defining the default value

Glad to hear the I2C interface is working. Checking the pins would have been my next port of call as you have the library setup ok.

It is interesting to note the pin differences between the Atmega328p and Atmega32U4 microcontrollers and how Sparkfun have named the pins on the board. This could lead to much confusion, if you dont use the libraries.

Atmega328p IC.

Atmega32U4 IC.
SCL D0, SDA D1, RX D2, TX D3,

Sparkfun Qduino board.
RX D0, TX D1, SDA D2, SCL D3