I didn't read all the way through. Seems to me like you have at least a
problem with how reading/writing of registers work. I think what you need
is something along the lines of:
byte readRegister(byte index) throws ... {
byte[] request = new byte[] { index };
byte[] response = new byte[1];
if (!i2c_bus.writeRead(ADDRESS, false, request, 1, response, 1)) {
throw ...
}
return response[0];
}
void writeRegister(byte index, byte value) throws ... {
byte[] request = new byte[] { index, value };
if (!i2c_bus.writeRead(ADDRESS, false, request, 2, null, 0)) {
throw ...
}
}
On top of that you can build everything else, i.e. your initialization
procedure as well as the data reading.
On Wed, Jul 8, 2015 at 11:33 AM, Armando Rojas <[email protected]>
wrote:
> Hi everyone, I need some help regarding IOIO and I2C.
>
> I'm working trying to read some data from an MPL3115A2 Breakout Board
> (Altitude / Barometric / Temperature sensor), device slave address is 0x60
> (7-bit), interface frequency set first at 100 KHz, now at 400 KHz (max.
> frequency admitted, according to datasheet). Since it is a breakout board,
> I connected directly the board to the IOIO (3.3v + GND, and SCL in pin 25,
> and SDA in pin 26. I didn't use other I2C because they're used already)
> without using pull-up resistors between the board and the IOIO in the clock
> and data lines. Meter shows voltage values up to 3.3v, so I assume that
> that IOIO pins (25 and 26) work at 3.3v maximum when in I2C mode using
> TwiMaster interface and using I2C voltage values, not the SMBus ones. Is
> that assumption correct? (I don't know very much of open-drain mode and
> related topics). I can read random binary data from the sensor but I
> couldn't make it readable, e.g. transforming some binary value in an
> altitude value. I'm assuming that sensor comes factory-calibrated.
>
> My question is the following: when I use the writeRead instruction, how
> does IOIO know which parts of the request are register addresses where I'm
> going to write to, which parts are values that I'm going to write into
> those registers, and which parts are register addresses where I just need
> to read their value? I'm assuming that I can make the three operations in
> the same instruction, the writing and querying operations first, and then
> the reading operations.
>
> The MPL3115A2 datasheet is located here:
> http://cache.freescale.com/files/sensors/doc/data_sheet/MPL3115A2.pdf
> For more information about the sensor/board:
> https://www.sparkfun.com/products/11084 (includes schematics)
>
> This is my initialization code (executed in the setup() method):
>
> private final byte altAddress = (byte)0x60;
> boolean transactResult;
> ...
>
> request = new byte[]{(byte)0x26,(byte)0b10000010};//First byte is a
> register adress, second byte is data being written there
> response = new byte[1];
> transactResult = sensAltitude.writeRead(altAddress, false, request,
> request.length, response, 1);
> if(!transactResult){//If transactResult is false, show error message
> System.out.println("Error while configuring the sensor.");
> }else{
> System.out.println("Setup Values:"+ new String(BinaryCodec.
> toAsciiString(response)));//BinaryCodec is from Apache Commons
> }
>
> //Same lines as before but information written now has the last bit set to
> 1 (sensor requirement)
> request = new byte[]{(byte)0x26,(byte)0b10000011};//First byte is a
> register adress, second byte is data being written there
> response = new byte[1];
> transactResult = sensAltitude.writeRead(altAddress, false, request,
> request.length, response, 1);
> if(!transactResult){//If transactResult is false, show error message
> System.out.println("Error while configuring the sensor.");
> }else{
> System.out.println("Setup Values:"+ new String(BinaryCodec.
> toAsciiString(response)));//BinaryCodec is from Apache Commons
> }
>
>
> And this is my loop code. It just reads from register 0x01 through 0x05
> where altitude and temperature data are. Then I just print the raw bits
> from the first three bytes of the response.
> 0x01 is the MSB of the Altitude/Pressure Data
> 0x02 is the CSB of the Altitude/Pressure Data
> 0x03 is the LSB of the Altitude/Pressure Data. According to the datasheet,
> only bytes 7-4 are used, as the LSB only represents the fractional part of
> the altitude.
> 0x04 is the MSB of the Temperature Data.
> 0x05 is the LSB of the Temperature Data.
>
> I assume that the bits inside each byte of the response are in order (from
> most significant to least significant) and there is no need to flip the
> order, and the bytes inside the response are in the same order as bytes
> requested (0x01, 0x02, etc.). According to the datasheet, only 0x01 and
> 0x02 are the integer part of the altitude and is represented in 2's
> compliment (total value, including fractional part, takes 20 bits, but the
> last 4 bits are unsigned).
>
> request = new byte[]{(byte)0x01,(byte)0x02,(byte)0x03,(byte)0x04,(byte)
> 0x05};response = new byte[5];//3 bytes para Altitud, 2 bytes para
> TemperaturasensAltitude.writeRead(altAddress, false, request, 0, response,
> response.length);byte[] altBits = new byte[3];altBits[0] =
> response[0];altBits[1] = response[1];altBits[2] = response[2];
> System.out.println("RAW ALT BITS:" + BinaryCodec.toAsciiString(
> altBits));ByteBuffer bb;//To perform byte-to-Short conversionbyte[]
> wholeAltBytes = new byte[2];wholeAltBytes[0] = request[0];wholeAltBytes[1]
> = request[1];
> bb = ByteBuffer.allocate(2);bb.clear();bb.put(request[0]);bb.put(request[1
> ]);bb.rewind();
> wholeAltitude = bb.getShort(); System.out.println("WHOLE ALT: " +
> wholeAltitude + " m");
>
>
>
> The results are the following. For the raw bits of ALT, I separated them
> in three 8-bit bytes, believing that the first will be MSB, the second CSB
> and the last LSB regarding the Altitude values. Then I wrote the
> transformed value (bits to short) of the MSB + CSB bits that the getShort()
> method of the ByteBuffer class provides. So the result format, for a better
> reading here is:
>
> Altitude MSB bits | Altitude CSB bits | Altitude LSB bits --- Short
> integer representing the "converted" value taken from the MSB and CSB bits.
> Values were obtained while I was moving the setup up and down more than 30
> cm (sensitivity range for altitude, I move it up and down about a meter).
> If I interpreted correctly, the Altitude LSB should be something like
> abcd0000, where a,b,c and d could be 0 or 1.
>
> 10110001 | 00000000 | 00000000 -- 258
> 10101110 | 00000000 | 00000000 -- 258
>
> I don't know why the short value always is 258. Not 257 or 259.
> So, where is the LSB? Why the MSB shows those values? They, apparently,
> have no sense, even if that is a negative integer!
>
> The values are doing between those two values. So I chose to print ALL the
> bits in the response (MSB,CSB,LSB bytes of Altitude, MSB and LSB bytes of
> Temperature, same format):
>
> 00010101 | 01010000 | 10110101 | 00000000 | 00000000
> 00010101 | 11010000 | 10110011 | 00000000 | 00000000
> 00010101 | 01000000 | 10110100 | 00000000 | 00000000
> 00010101 | 00010000 | 10110011 | 00000000 | 00000000
>
> It seems that the second byte has the four last bits always in zero. Is
> that the Altitude LSB? Why is it there?
>
> I have some knowledge/experience in Java, but I'm working with IOIO since
> 1 month or a bit more only, and with I2C just 4 or 5 days. This is the only
> sensor in my setup that uses that protocol, and all examples for this
> sensor are Arduino-based, so I don't know what is going on when I perform a
> writeRead. If I move the sensor, raw binary data seems to change, but I
> can't interpret that. Excuse me if I made some grammar mistakes, English is
> not my mother tongue.
>
> If anyone is wondering, I don't have a oscilloscope but maybe I ask for
> one as last resort. I'll need help trying to use it, though.
>
> Thank you in advance!
>
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