I2C on Stellaris Launchpad

[sq7bti 20]

Have you tried the NXP PCF2129A instead?

 

The PCF2129A operates at 3.3V, embeds the quartz crystal and requires no passive components, except the 10kΩ pull-up resistors for the I²C bus.

 

Actually, the LM4F120 / TM4C123 already includes a RTC, but the battery power line for LPM is connected to the main power line.

 

I got it all up and running with 1307, just as I wrote: V_bus as supply (5V) and with 3.3V on pullup i²c resistors. PCF is not available in DIP, while DS1307 is. Thanks for the hint anyway.

 

Addendum: Besides, the DS1307 features an NVRAM. Comes handy for the project I am working on right now: newtonian telescope controller: store mount specific configuration instead of compile-in.

Edited May 16, 2014 by sq7bti

[altineller 4]

There's a trick with I2C port 3 on the LaunchPads LM4F120 and TM4C123.

 

Capture 2014-05-04 20-14-42.png

 

Just remove R9 and R10.

 

Hello Reil,

 

Could you explain this a little further? you mean remove R9 and R10 from the launchpad?

 

What will happen when they are removed?

 

Best Regards,

[Rei Vilo 695]

Just have a look at the datasheet of the LaunchPad Stellaris - Tiva C. When you remove the shunts, I²C is no longer redirected to pins 14 and 15.

 

I²C on pins 14 and 15 complies with the old BoosterPack standard, where MSP430 MCUs bring SPI and I²C to those pins. So main benefit is you use SPI on pins 14 and 15 without sacrificing an I²C port on pins 23 and 24. Please note this is only valid for the LaunchPad Stellaris LM4F120 - Tiva C TM4C123.

 

On today's standard for BoosterPacks, I²C is on pins 9 and 10.

[altineller 4]

Just have a look at the datasheet of the LaunchPad Stellaris - Tiva C. When you remove the shunts, I²C is no longer redirected to pins 14 and 15.

 

I²C on pins 14 and 15 complies with the old BoosterPack standard, where MSP430 MCUs bring SPI and I²C to those pins. So main benefit is you use SPI on pins 14 and 15 without sacrificing an I²C port on pins 23 and 24. Please note this is only valid for the LaunchPad Stellaris LM4F120 - Tiva C TM4C123.

 

On today's standard for BoosterPacks, I²C is on pins 9 and 10.

 

Yes I have figured that out the hard way.

 

Anyways, now my mpu9150Lib port to energia is working better. I get:

 

Init MPU9150.

Setting up compass.

Compass sens: 298 299 312

Loading DMP firmware

Firmware loaded

46

47

45

46

49

47

 

But the sensor rate will not go less than 45ms. on arduino nano, I can get 100hz (10ms) reading from this sensor, making it really nice.

 

Previously, I had those shunt resistors, that was making dmp load some of the time and not some of the time. Now I fixed them and there is the speed problem.

 

I am looking at the MPU9150Lib code, and see that no micros used, (only millis for timing)

 

I am sure it is a clocking problem, because, when i run the same library in arduino due, i get the same exact problem. it has to be an i2c quirk.

 

Best Regards,

C.A.

[Rei Vilo 695]

Contrary to the AVR MCUs on the Arduino boards, the Stellaris - Tiva C has no internal pull-up resistors. External pull-up resistors are thus highly recommended. I'm using 10 k ohm.

[Rei Vilo 695]

I've one SensorHub BoosterPack with a MPU9150. I could give a try: would you mind posting the link to the library you're using and to the part of your sketch relevant to the IMU configuration and management? Thank you.

[Nguyen Minh Minh 0]

Can you please share the link to download wire.h