From: marshmellow42 <marshmellow42@users.noreply.github.com>
Date: Mon, 21 Aug 2017 19:29:56 +0000 (-0400)
Subject: Merge pull request #356 from pwpiwi/low_frequencies
X-Git-Tag: v3.1.0~178
X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/commitdiff_plain/fe087813f65b2a08ee814ad78d1164ae7eac6db0?hp=d0067d0768e26f100837609a75072da08950e456

Merge pull request #356 from pwpiwi/low_frequencies

revert removal of quarter frequency support for hi_read_rx_xcorr.v
---

diff --git a/armsrc/fpgaloader.h b/armsrc/fpgaloader.h
index 59c07ed8..7dfc5c12 100644
--- a/armsrc/fpgaloader.h
+++ b/armsrc/fpgaloader.h
@@ -58,6 +58,7 @@ void SetAdcMuxFor(uint32_t whichGpio);
 // Options for the HF reader, correlating against rx from tag
 #define FPGA_HF_READER_RX_XCORR_848_KHZ				(1<<0)
 #define FPGA_HF_READER_RX_XCORR_SNOOP				(1<<1)
+#define FPGA_HF_READER_RX_XCORR_QUARTER_FREQ		(1<<2)
 // Options for the HF simulated tag, how to modulate
 #define FPGA_HF_SIMULATOR_NO_MODULATION				(0<<0)
 #define FPGA_HF_SIMULATOR_MODULATE_BPSK				(1<<0)
diff --git a/fpga/fpga_hf.bit b/fpga/fpga_hf.bit
index 864b5239..b9f2e629 100644
Binary files a/fpga/fpga_hf.bit and b/fpga/fpga_hf.bit differ
diff --git a/fpga/fpga_hf.v b/fpga/fpga_hf.v
index 264e1b0c..f99a43dd 100644
--- a/fpga/fpga_hf.v
+++ b/fpga/fpga_hf.v
@@ -73,6 +73,8 @@ wire hi_read_tx_shallow_modulation = conf_word[0];
 wire hi_read_rx_xcorr_848 = conf_word[0];
 // and whether to drive the coil (reader) or just short it (snooper)
 wire hi_read_rx_xcorr_snoop = conf_word[1];
+// divide subcarrier frequency by 4
+wire hi_read_rx_xcorr_quarter = conf_word[2];
 
 // For the high-frequency simulated tag: what kind of modulation to use.
 wire [2:0] hi_simulate_mod_type = conf_word[2:0];
@@ -100,7 +102,7 @@ hi_read_rx_xcorr hrxc(
 	hrxc_ssp_frame, hrxc_ssp_din, ssp_dout, hrxc_ssp_clk,
 	cross_hi, cross_lo,
 	hrxc_dbg,
-	hi_read_rx_xcorr_848, hi_read_rx_xcorr_snoop
+	hi_read_rx_xcorr_848, hi_read_rx_xcorr_snoop, hi_read_rx_xcorr_quarter
 );
 
 hi_simulate hs(
diff --git a/fpga/hi_read_rx_xcorr.v b/fpga/hi_read_rx_xcorr.v
index 80e36327..afa46c44 100644
--- a/fpga/hi_read_rx_xcorr.v
+++ b/fpga/hi_read_rx_xcorr.v
@@ -10,7 +10,7 @@ module hi_read_rx_xcorr(
     ssp_frame, ssp_din, ssp_dout, ssp_clk,
     cross_hi, cross_lo,
     dbg,
-    xcorr_is_848, snoop
+    xcorr_is_848, snoop, xcorr_quarter_freq
 );
     input pck0, ck_1356meg, ck_1356megb;
     output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
@@ -20,7 +20,7 @@ module hi_read_rx_xcorr(
     output ssp_frame, ssp_din, ssp_clk;
     input cross_hi, cross_lo;
     output dbg;
-    input xcorr_is_848, snoop;
+    input xcorr_is_848, snoop, xcorr_quarter_freq;
 
 // Carrier is steady on through this, unless we're snooping.
 assign pwr_hi = ck_1356megb & (~snoop);
@@ -28,19 +28,21 @@ assign pwr_oe1 = 1'b0;
 assign pwr_oe3 = 1'b0;
 assign pwr_oe4 = 1'b0;
 
-// Clock divider
-reg [0:0] fc_divider;
+reg [2:0] fc_div;
 always @(negedge ck_1356megb)
-    fc_divider <= fc_divider + 1;
-wire fc_div2 = fc_divider[0];
+    fc_div <= fc_div + 1;
 
-reg adc_clk;
-always @(ck_1356megb)
-	if (xcorr_is_848)
+(* clock_signal = "yes" *) reg adc_clk;				// sample frequency, always 16 * fc
+always @(ck_1356megb, xcorr_is_848, xcorr_quarter_freq, fc_div)
+	if (xcorr_is_848 & ~xcorr_quarter_freq)			// fc = 847.5 kHz
 		adc_clk <= ck_1356megb;
-	else
-		adc_clk <= fc_div2;
-
+	else if (~xcorr_is_848 & ~xcorr_quarter_freq)	// fc = 424.25 kHz 
+		adc_clk <= fc_div[0];
+	else if (xcorr_is_848 & xcorr_quarter_freq)		// fc = 212.125 kHz
+		adc_clk <= fc_div[1];
+	else 											// fc = 106.0625 kHz
+		adc_clk <= fc_div[2];
+		
 // When we're a reader, we just need to do the BPSK demod; but when we're an
 // eavesdropper, we also need to pick out the commands sent by the reader,
 // using AM. Do this the same way that we do it for the simulated tag.
@@ -71,8 +73,7 @@ end
 // so we need a 6-bit counter.
 reg [5:0] corr_i_cnt;
 // And a couple of registers in which to accumulate the correlations.
-// we would add at most 32 times adc_d, the result can be held in 13 bits. 
-// Need one additional bit because it can be negative as well
+// we would add/sub at most 32 times adc_d, the signed result can be held in 14 bits. 
 reg signed [13:0] corr_i_accum;
 reg signed [13:0] corr_q_accum;
 reg signed [7:0] corr_i_out;
@@ -84,7 +85,7 @@ reg ssp_frame;
 
 always @(negedge adc_clk)
 begin
-		corr_i_cnt <= corr_i_cnt + 1;
+	corr_i_cnt <= corr_i_cnt + 1;
 end