I2C MMA8452 Accelerometer

[emf985]

I connected to the I2C bus 4 chips that work perfect ,I can read and write without any problem,
(2 x PCA9532 - LED drivers,MAX17043 - Fuel Gauge, DS1307 - RTC).but the MMA8452 returns only zeros.
I tried slow ans high speeds,I2C_HOLD but failed.
I use the PIC18F2553 at 48MHz
The compiler is PBP 2.6
Help,Please....

[emf985]

I read the datasheet and it says:"Single Byte ReadThe MMA8453Q has an internal ADC that can sample, convert and return sensor data on request. The transmission of an
8-bit command begins on the falling edge of SCL. After the eight clock cycles are used to send the command, note that the data
returned is sent with the MSB first once the data is received. Figure 11 shows the timing diagram for the accelerometer 8-bit I2C
read operation. The Master (or MCU) transmits a start condition (ST) to the MMA8453Q, slave address ($1D), with the R/W bit
set to “0” for a write, and the MMA8453Q sends an acknowledgement. Then the Master (or MCU) transmits the address of the
register to read and the MMA8453Q sends an acknowledgement. The Master (or MCU) transmits a repeated start condition (SR)
and then addresses the MMA8453Q ($1D) with the R/W bit set to “1” for a read from the previously selected register. The Slave
then acknowledges and transmits the data from the requested register. The Master does not acknowledge (NAK) the transmitted
data, but transmits a stop condition to end the data transfer."
How can I send a repeated start?

[rsocor01]

but the MMA8452 returns only zeros.

I assume that you are using a different address for every device. Isolate the MMA8452 and try to communicate with it first.

[emf985]

Thanks
Yes,of course ,the problem, as I see it , is that the pbp cannot produce a repeated start .
I used a logic analizer -----> the accelerometer sends acknowlage signals.
the data sheet demands an Sr (repeat start) in order to read the device.
the device resets the address register to zero if the master sends a STOP.
I can read only the top seven registers only.(there are a lot of registers).

[pedja089]

Maybe this will help you.
http://www.picbasic.co.uk/forum/cont...-EEPROM-Part-1

[emf985]

Thanks,I read it,( there is no part 2) .
I used PBP I2CREAD and I2CWRITE instructions .
Maby there is something to be done with the instructions we have,I hope I'll not be forced to write new I2C subrutines just for this device.(hopefully somone did write it)

[pedja089]

This is I2C write:
GOSUB INT_ROM
SHIFTOUT DPIN,CPIN,1,[DATO\8,%1\1]
GOSUB STOP_ROM

I2CREAD:
GOSUB INT_ROM
GOSUB START_ROM
SHIFTOUT DPIN,CPIN,1,[CONT1]
SHIFTIN DPIN,CPIN,0,[ACK\1,DATI\8]
SHIFTOUT DPIN,CPIN,1,[%1\1]
GOSUB STOP_ROM

This is start sequence:
START_ROM:
HIGH CPIN:HIGH DPIN:LOW DPIN:RETURN

Every thing is already done...