I2C Communications

Question

Hi guys! I have a sensor module that I am trying to use. I can't seem to get it working with I2C.

Does anyone have any tips or can anyone point me to any useful materials to help me make progress with this sensor?

The sensor is a 3 axis magnetometer.

Thanks!

koudelad · Answer

If you prefer a video tutorial, Ben Hack made one:

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Depending on how serious you are with electronics, I can recommend buying a logic analyzer (some cheap cost a few dollars). Or, some microcontroller programmers have support for various protocols analysis (UART, I2C, SPI). This allows you to test any new sensor/device with a piece of HW and SW that is proven to work and later makes it easier to debug your own HW and firmware. Almost all microcontroller families now have an integrated I2C module and most development environments have ready made libraries for it.

clem57 · Answer

You do not show any details, so a general tutorial may help https://learn.sparkfun.com/tutorials/i2c

koudelad · Answer

I've quickly gone through the linked datasheet and I think you only have to properly set MR_REG_M register in order to start measuring. By default (after reset), it is in sleep-mode.

koudelad · Answer

To be honest, I am also struggling with debugging PSoCs in PSOC Creator. Compared to debugging PICs, it is quite limited. (Must go deeper to make sure I am not using it wrong.) That's why I recommended a logic analyser. You can easily read/write the entire memory of the sensor and quickly check all values against the datasheet. If you are interested, I can insert some working I2C code for PSoC 5LP (it is probably the same for PSOC 4) I used for a real time clock.

clem57 · Answer

Here is example http://www.psocdeveloper.com/project/psoc4-i2c-communication/

koudelad · Answer

The code below is the minimum I extracted from my project and should be general enough. I've worked with DS3232M RTC. The component name (placed in the design) is I2C and microcontroller used is some PSOC 5LP series. I am not sure about the original source, but I think this code comes from a Cypress application note (I've just opened a few, but couldn't find it). This code doesn't check for I2C component availability etc. and as provided is useless (nothing is done with the data). I only pasted the functions to perform a single read from the I2C slave device. #define I2C_WRITE 0u
#define I2C_READ 1u
#define RTC_I2C_ADDRESS 0x68 // I2C address of DS3232M (and some other RTCs)
#define RTC_RAM_TD_LOCATION 0u // RAM location of current time and date
#define RTC_NO_OF_BYTES_FULL 255u // number of bytes to read full RTC RAM

void RTC_I2C_Read_RAM (unsigned char ramLocation, unsigned char bytesCount, unsigned char *i2cBuffer) {
 I2C_MasterSendStart(RTC_I2C_ADDRESS, I2C_WRITE);
 I2C_MasterWriteByte(ramLocation);
 I2C_MasterReadBuf(RTC_I2C_ADDRESS, i2cBuffer, bytesCount, (I2C_MODE_REPEAT_START | I2C_MODE_COMPLETE_XFER)); 
}

uint8 i2cRTCReadBufferFull[256]; // buffer big enough to store full RAM of RTC clock

int main(void)
{
 CyGlobalIntEnable; /* Enable global interrupts. */

I2C_Start(); // start I2C component

RTC_I2C_Read_RAM(RTC_RAM_TD_LOCATION, RTC_NO_OF_BYTES_FULL, i2cRTCReadBufferFull); // read the whole RAM of DS3232M

for(;;) {;}
}

rbevy101 · Answer

The variables in the main loop had to be moved outside to make them global. Spot the rookie haha

I2C Communications

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