Added LF frequency adjustments from d18c7db, cleaned up code,

[proxmark3-svn] / fpga / lo_read.v

//-----------------------------------------------------------------------------\r
// The way that we connect things in low-frequency read mode. In this case\r
// we are generating the 134 kHz or 125 kHz carrier, and running the\r
// unmodulated carrier at that frequency. The A/D samples at that same rate,\r
// and the result is serialized.\r
//\r
// Jonathan Westhues, April 2006\r
//-----------------------------------------------------------------------------\r
\r
module lo_read(\r
    pck0, ck_1356meg, ck_1356megb,\r
    pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,\r
    adc_d, adc_clk,\r
    ssp_frame, ssp_din, ssp_dout, ssp_clk,\r
    cross_hi, cross_lo,\r
    dbg,\r
    lo_is_125khz, divisor\r
);\r
    input pck0, ck_1356meg, ck_1356megb;\r
    output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;\r
    input [7:0] adc_d;\r
    output adc_clk;\r
    input ssp_dout;\r
    output ssp_frame, ssp_din, ssp_clk;\r
    input cross_hi, cross_lo;\r
    output dbg;\r
    input lo_is_125khz;\r
    input [7:0] divisor;\r
\r
// The low-frequency RFID stuff. This is relatively simple, because most\r
// of the work happens on the ARM, and we just pass samples through. The\r
// PCK0 must be divided down to generate the A/D clock, and from there by\r
// a factor of 8 to generate the carrier (that we apply to the coil drivers).\r
//\r
// This is also where we decode the received synchronous serial port words,\r
// to determine how to drive the output enables.\r
\r
// PCK0 will run at (PLL clock) / 4, or 24 MHz. That means that we can do\r
// 125 kHz by dividing by a further factor of (8*12*2), or ~134 kHz by\r
// dividing by a factor of (8*11*2) (for 136 kHz, ~2% error, tolerable).\r
\r
reg [7:0] to_arm_shiftreg;\r
reg [7:0] pck_divider;\r
reg [6:0] ssp_divider;\r
reg ant_lo;\r
\r
always @(posedge pck0)\r
begin\r
	if(pck_divider == 8'd0)\r
		begin\r
			pck_divider <= divisor[7:0];\r
			ant_lo = !ant_lo;\r
			if(ant_lo == 1'b0)\r
			begin\r
			    ssp_divider <= 7'b0011111;\r
				to_arm_shiftreg <= adc_d;\r
			end\r
		end\r
	else\r
	begin\r
		pck_divider <= pck_divider - 1;\r
		if(ssp_divider[6] == 1'b0)\r
		begin\r
			if (ssp_divider[1:0] == 1'b11) to_arm_shiftreg[7:1] <= to_arm_shiftreg[6:0];\r
			ssp_divider <= ssp_divider - 1;\r
		end\r
	end\r
end\r
\r
assign ssp_din = to_arm_shiftreg[7];\r
assign ssp_clk = pck_divider[1];\r
assign ssp_frame = ~ssp_divider[5];\r
assign pwr_hi = 1'b0;\r
assign pwr_lo = ant_lo;\r
assign adc_clk = ~ant_lo;\r
assign dbg = adc_clk;\r
endmodule\r