Jerry-rig a simply hysteresis based receiver into hi_read_tx. Output is via SSC_DIN...

[proxmark3-svn] / fpga / lo_passthru.v

//-----------------------------------------------------------------------------\r
// For reading TI tags, we need to place the FPGA in pass through mode\r
// and pass everything through to the ARM\r
//-----------------------------------------------------------------------------\r
\r
module lo_passthru(\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, 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 [7:0] divisor;\r
\r
reg [7:0] pck_divider;\r
reg ant_lo;\r
\r
// this task runs on the rising egde of pck0 clock (24Mhz) and creates ant_lo\r
// which is high for (divisor+1) pck0 cycles and low for the same duration\r
// ant_lo is therefore a 50% duty cycle clock signal with a frequency of\r
// 12Mhz/(divisor+1) which drives the antenna as well as the ADC clock adc_clk\r
always @(posedge pck0)\r
begin\r
	if(pck_divider == divisor[7:0])\r
		begin\r
			pck_divider <= 8'd0;\r
			ant_lo = !ant_lo;\r
		end\r
	else\r
	begin\r
		pck_divider <= pck_divider + 1;\r
	end\r
end\r
\r
// the antenna is modulated when ssp_dout = 1, when 0 the\r
// antenna drivers stop modulating and go into listen mode\r
assign pwr_oe3 = 1'b0;\r
assign pwr_oe1 = ssp_dout;\r
assign pwr_oe2 = ssp_dout;\r
assign pwr_oe4 = ssp_dout;\r
assign pwr_lo = ant_lo && ssp_dout;\r
assign pwr_hi = 1'b0;\r
assign adc_clk = 1'b0;\r
assign ssp_din = cross_lo;\r
assign dbg = cross_lo;\r
\r
endmodule\r