Questions about the Transparent mode.
The ST25R200 is cheaper then discrete components for a non-standard RFID interface ( at 848 KHz subcarrier )
Questions about the transparent mode:
I am struggling with the receiver in this mode.
( An example with signal values from an oscilloscope, to just send a command and get the response would be enough.
I assume the reponse being 10% modulation from the tag using the 848KHz subcarrier, for 102Kb/s standard bitrate. )
Could someone give an indication about the signals coming out of the transparant mode.
Is there a document?
Just showing the TX being used to 'send a command' and the response on the receive channel would be really helpful
In the picture in the datasheet, the receiver does have a 848KHz ( fs/16 ) receiver, followed by a dual ADC.
( Is this a real ADC or just a comparator ? )
( I and Q , I assume what is their sample rate ? 848 Khz, are these one bitter ? See questions further on)
After these ADC there is a correlator ( Is this on the I and Q, or on the modulus of the I/Q ? )
In the transparent mode signals are: ( TX and RX are both enabled )
( Do these signals need to have a certain relation to the 2 x 13.56 system clock in the ST25R200 ??, set-up and hold ?? Or are they asynchronouys or synchronized to the clock ? )
MOSI Transmitter modulation - high is modulator on
SCLK Enable reception (rx_on) - high enables reception chain and AGC
MISO
In case dis_corr=0, correlator data output (sum of I+Q)
In case dis_corr=1, output of receiver I reception chain (digitized subcarrier signal)
IRQ
In case dis_corr=0, correlator start signal (subcarrier detected)
In case dis_corr=1, output of receiver Q reception chain (digitized subcarrier signal)
MOSI-pin: This is clear, you can able enable and disable the TX signal at the antenna.
Are there any ramp-up and ramp-down timings and maybe some delay ?
( I may need to know to be able to calculate the delay between a 'TX' command and a standard TAG response time )
SCLK: enable reception chain: this is clear
MISO: dis_corr=0: This is a single line, so what does sum of I+Q mean ? Is it a one when the modulus of the vector sum of I and Q is above '1' ??
dis_corr=1: The I channel.
Is it at the the current 848KHz subcarrier sample rate, just being the digitized subcarrier.
Is this digitized subcarrier multiplied with the expected 102KHz bit rate and then sampled at 848KHz ??
IRQ : dis_corr=0: Subcarrier detected. Does this mean a clear 0->1 or 1->0 edge was detected. So it means as long as there is no return data it does not detect the subcarrier ?
dis_corr=1: output of the receiver Q channel. the receiver incoming subcarrier multiplied with the expected bit value ? sampled at 848KHz ?
