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Some questions about the FXTH87 and MC33696

Question asked by Jiangbo Li on Sep 23, 2015

I recently is studying tire pressure monitoring system(TPMS) base on the FXTH870911DT1.

I use the MC33696 evaluation board and MC9S08RG60 demo board as the receiver.

I have now realized the communication between the FXTH870911DT1 and the MC33696,but there is a problem,A detailed description is as follows

 

As the transmitter,FXTH87 configuration information is as follows

1.Mode:FSK

2.Frequency:433.92MHz

3.Band rate:4800

4.Frame format:Praemble + ID + Header + data + EOM

                           0B1111 + 0B110101 + 0B100001 + 0B00001111 + EOM(RFCR2_EOM = 1)

         RF Buffer:0xFD,0x61,0x0F

          TPMS_RF_SET_TX(23);

 

As the receiver,MC33696 configuration information is as follows

1.Mode:FSK

2.Frequency:433.92MHz

3.Band rate:4800

4.DME:1

5.ID:F5

6.Header:E1

 

I receive the data by the Hyperterminal(MC33696 evaluation board + MC9S08RG60 demo board),now I can receive the  0B00001111(0x0F),the data is correct,

but I receive the 0B0000111111111111 (0x0FFF)randomly.

I try to change the data,RF Buffer:0xFD,0x61,0xF0,I receive the all data is 0B1111000011111111(0xF0FF) or 0B1111000001111111(0xF07F)

Then I clear the RFCR2_EOM,but all of the phenomenon is the same as described above.

I don't know why I receive the 0xFF and 0x7F eatra?

Can anyone help me.Thanks.

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