proxmark3/fpga/lo_read.v
iZsh b014c96d68 new command "lf snoop" to snoop raw ADC values
fpga/lo_read.v (lf_field): new argument.
fpga/fpga_lf.v: modify accordingly.

armsrc/apps.h (FPGA_MAJOR_MODE_LF_READER): Rename as FPGA_MAJOR_MODE_LF_ADC.
armsrc/apps.h (FPGA_LF_ADC_READER_FIELD): New LF option.
armsrc/lfops.c: Modify accordingly.

client/cmdlf.c (CmdLFSnoop): New command.
armsrc/appmain.c, armsrc/lfops.c, client/cmdlf.h, include/usb_cmd.h: Modify accordingly.
2014-06-21 21:33:54 +02:00

75 lines
2.8 KiB
Verilog

//-----------------------------------------------------------------------------
// The way that we connect things in low-frequency read mode. In this case
// we are generating the unmodulated low frequency carrier.
// The A/D samples at that same rate and the result is serialized.
//
// Jonathan Westhues, April 2006
// iZsh <izsh at fail0verflow.com>, June 2014
//-----------------------------------------------------------------------------
module lo_read(
input pck0, input [7:0] pck_cnt, input pck_divclk,
output pwr_lo, output pwr_hi,
output pwr_oe1, output pwr_oe2, output pwr_oe3, output pwr_oe4,
input [7:0] adc_d, output adc_clk,
output ssp_frame, output ssp_din, output ssp_clk,
output dbg,
input lf_field
);
reg [7:0] to_arm_shiftreg;
// this task also runs at pck0 frequency (24Mhz) and is used to serialize
// the ADC output which is then clocked into the ARM SSP.
// because pck_divclk always transitions when pck_cnt = 0 we use the
// pck_div counter to sync our other signals off it
// we read the ADC value when pck_cnt=7 and shift it out on counts 8..15
always @(posedge pck0)
begin
if((pck_cnt == 8'd7) && !pck_divclk)
to_arm_shiftreg <= adc_d;
else begin
to_arm_shiftreg[7:1] <= to_arm_shiftreg[6:0];
// simulation showed a glitch occuring due to the LSB of the shifter
// not being set as we shift bits out
// this ensures the ssp_din remains low after a transfer and suppresses
// the glitch that would occur when the last data shifted out ended in
// a 1 bit and the next data shifted out started with a 0 bit
to_arm_shiftreg[0] <= 1'b0;
end
end
// ADC samples on falling edge of adc_clk, data available on the rising edge
// example of ssp transfer of binary value 1100101
// start of transfer is indicated by the rise of the ssp_frame signal
// ssp_din changes on the rising edge of the ssp_clk clock and is clocked into
// the ARM by the falling edge of ssp_clk
// _______________________________
// ssp_frame__| |__
// _______ ___ ___
// ssp_din __| |_______| |___| |______
// _ _ _ _ _ _ _ _ _ _
// ssp_clk |_| |_| |_| |_| |_| |_| |_| |_| |_| |_
// serialized SSP data is gated by ant_lo to suppress unwanted signal
assign ssp_din = to_arm_shiftreg[7] && !pck_divclk;
// SSP clock always runs at 24Mhz
assign ssp_clk = pck0;
// SSP frame is gated by ant_lo and goes high when pck_divider=8..15
assign ssp_frame = (pck_cnt[7:3] == 5'd1) && !pck_divclk;
// unused signals tied low
assign pwr_hi = 1'b0;
assign pwr_oe1 = 1'b0;
assign pwr_oe2 = 1'b0;
assign pwr_oe3 = 1'b0;
assign pwr_oe4 = 1'b0;
// this is the antenna driver signal
assign pwr_lo = lf_field & pck_divclk;
// ADC clock out of phase with antenna driver
assign adc_clk = ~pck_divclk;
// ADC clock also routed to debug pin
assign dbg = adc_clk;
endmodule