Help with MLX90121 RFID reader

[amila.ediri]

mlx90121

I'm using a MLX 90121 RFID reader and using ISO15693 standard. I have built the reference circuit given in the device data sheet and it s outputting decent amount of power. I have written the firmware for the chip implementing the standard for an Inventory request.
The problem is im not getting any response from the tag. What can be the problem?
Can some one help me on this.
Thank You

 

[rajeshkumar123]

firmware mlx90121

Hi,

Check if the RF circuit is as recommended in te datasheet. Is the digital interface between the controller and the IC working? What is the controller you are using ?

 

[amila.ediri]

mlx90121 based reader

Hi!
Thnx for the reply.
Well the circuit is built according to the given schematic. And we can see that the transmission is happening. We are using a PIC16F877.
May b the problem is with the implementation of ISO15693 protocol by us. We wrote the code for an inventory request for a known UID and used that tag. Here s how the Inventory request bit pattern was decided.

making of inventory request bit pattern.

#sof

#flags

? bit 1 is LSb or MSb. I take as LSb.

bit 1: 0 //single subcarrier is used.
bit 2: 1 //high data rate is used: 1 out of 4.
bit 3: 1 //inventory request.
bit 4: 0 //no protocol extension is used.

bit 5: 0 //AFI flag is not set.
bit 6: 1 //one slot is used: no anti-collision algorithm implemented.
bit 7: 0 // no options
bit 8: 0 //RFU.



#command code

0x01 for the inventory request.


$$ for the following, let us assume our UID is 0x123456789ABCDEF1


#parameters: mask length is the parameter.

let's take the mask length as 5 bits.
0x05.

#data: mask value is the data.

so we need our mask to be 00010001, as these are the LSbits of the UID.

#crc

#eof

the bits upto now;

flags : 00 10 01 10 : 0x26
command :00 00 00 01 : 0x01
mask length : 00 00 01 01 : 0x05
mask : 00 01 00 01 : 0x11


CRC calculated : 0xDB88
send 0x88 0xDB :
10 00 10 00 11 10 11 00

so message to send

sof 0x26 0x01 0x05 0x11 0x88 0xDB eof




sof 10 01 10 00 01 00 00 00 01 01 00 00 01 00 01 00 00 10 00

10 00 11 10 11 eof

the final symbol pattern to send
s4 s2 s1 s2 s0 s1 s0 s0 s0 s1 s1 s0 s0 s1 s0 s1 s0 s0 s2 s0 s2 s0 s3 s2 s3 s5

Can you plz tell me whether there is anything wrong with the bit sequence.
Thanx a lot