CHG: updated some comments. I still think I don't understand this code

diff --git a/armsrc/iso14443b.c b/armsrc/iso14443b.c
index 68f0c366865142967db2f23beebd6ec20a5276c6..ed035d3a5e29d780a248da43ea2ca14dbee41e69 100644 (file)
--- a/armsrc/iso14443b.c
+++ b/armsrc/iso14443b.c
@@ -216,16 +216,19 @@ static void CodeIso14443bAsTag(const uint8_t *cmd, int len) {
        *  -TO VERIFY THIS BELOW-
        * The mode FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_BPSK which we use to simulate tag
        * works like this:  
-       * - A 1-bit input to the FPGA becomes 8 pulses at 847.5kHz (9.44µS)
-       * - A 0-bit input to the FPGA becomes an unmodulated time of 9.44µS
-       *
+       * - A 1-bit input to the FPGA becomes 8 pulses at 847.5kHz (1.18µS / pulse) == 9.44us
+       * - A 0-bit input to the FPGA becomes an unmodulated time of 1.18µS  or does it become 8 nonpulses for 9.44us
        *
+       * FPGA doesn't seem to work with ETU.  It seems to work with pulse / duration instead.
        * 
        * Card sends data ub 847.e kHz subcarrier
-       * 848k = 9.44µS  = 128 fc
-       * 424k = 18.88µS = 256 fc
-       * 212k = 37.76µS = 512 fc
-       * 106k = 75.52µS = 1024 fc
+       * subcar |duration| FC division
+       * -------+--------+------------
+       * 106kHz | 9.44µS | FC/128
+       * 212kHz | 4.72µS | FC/64
+       * 424kHz | 2.36µS | FC/32
+       * 848kHz | 1.18µS | FC/16
+       * -------+--------+------------
        *
        *  Reader data transmission:
        *   - no modulation ONES
@@ -496,8 +499,7 @@ void ClearFpgaShiftingRegisters(void){
        while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY)) {};
 
        b = AT91C_BASE_SSC->SSC_RHR; (void) b;
-       
-               
+                       
        // wait for the FPGA to signal fdt_indicator == 1 (the FPGA is ready to queue new data in its delay line)
        for (uint8_t j = 0; j < 5; j++) {       // allow timeout - better late than never
                while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));