On Sun, Oct 11, 2009 at 1:38 AM, MicVM <ssj2mi...@gmail.com> wrote: > > I am trying to build a vala library to access the accelerometers of the > freerunner. I am using vala just to give it a try but I am experiencing > strange problems and wanted to ask if some of you can give me some hints. > When i read from the input interface of an accelerometer i get the > following > bytestream: > > b 3 d1 4a 42 ea d 0 0 0 0 0 0 0 0 0 > 1b 3 d1 4a 79 f e 0 3 0 1 0 6c 0 0 0 > 1b 3 d1 4a d7 f e 0 3 0 2 0 26 4 0 0 > > that looks quite good to me. However, when I try to read the values in the > message as integers i have a problem when reding the "value" field, i.e. > the > last 32 bit signed integer of the message. I get strange values around +300 > instead of +1062 for the Z value as in the last line of the above example. > Also for X and Y the values are wrong. I read the stream with the following > code snippet in vala (using GIO libs): > > var data_stream=new DataInputStream(file_stream); > data_stream.set_byte_order(DataStreamByteOrder.LITTLE_ENDIAN); > > //Skip time field, 8 bytes > data_stream.skip(8,null); > > //Read eventtype > eventtype=data_stream.read_uint16(null); > while(eventtype!=0) > { > if((eventtype==3)||(eventtype==2)) > { > code=data_stream.read_uint16(null); > if(code==0) > { > x_value=data_stream.read_int32(null); > > } > if(code==1) > { > y_value=data_stream.read_int32(null); > } > if(code==2) > { > z_value=data_stream.read_int32(null); > } > > .... > > I think somewhere I am doing a major mistake because the decoding of the > int32 is a basic functionality that does not work in my case. The funny > thing is that decoding of uint16 is done correctly such that eventtype and > code are read correctly. Any help is appreciate :) > -- > View this message in context: > http://n2.nabble.com/Vala-DataInputStream-read-int32-in-accelerometer-message-tp3801000p3801000.html > Sent from the Openmoko Devel mailing list archive at Nabble.com. > > _______________________________________________ > devel mailing list > devel@lists.openmoko.org > https://lists.openmoko.org/mailman/listinfo/devel >
What is the maximum frequency at which you are able to read the accelerometer values? Are you able to sample the values properly? Are the reading in X and Y changing smoothly? Here is a test that I conducted: http://www.youtube.com/watch?v=Bdads8XAYcE&feature=fvsr Sriranjan
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