X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/7bc95e2e43c0b00b72fc794b18c26a880ac19d1c..a631936e84fa35d04bef9c45928ee602a258d6c4:/fpga/hi_iso14443a.v?ds=sidebyside diff --git a/fpga/hi_iso14443a.v b/fpga/hi_iso14443a.v index 0f7325b6..3f614fdd 100644 --- a/fpga/hi_iso14443a.v +++ b/fpga/hi_iso14443a.v @@ -29,43 +29,31 @@ module hi_iso14443a( output dbg; input [2:0] mod_type; -reg ssp_clk; -reg ssp_frame; -wire adc_clk; -assign adc_clk = ck_1356meg; +wire adc_clk = ck_1356meg; + -reg after_hysteresis, after_hysteresis_prev1, after_hysteresis_prev2, after_hysteresis_prev3, after_hysteresis_prev4; + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// Reader -> PM3: +// detecting and shaping the reader's signal. Reader will modulate the carrier by 100% (signal is either on or off). Use a +// hysteresis (Schmitt Trigger) to avoid false triggers during slowly increasing or decreasing carrier amplitudes +reg after_hysteresis; reg [11:0] has_been_low_for; -reg [8:0] saw_deep_modulation; -reg [2:0] deep_counter; -reg deep_modulation; always @(negedge adc_clk) begin - if(& adc_d[7:6]) after_hysteresis <= 1'b1; // adc_d >= 196 (U >= 3,28V) -> after_hysteris = 1 - else if(~(| adc_d[7:4])) after_hysteresis <= 1'b0; // if adc_d <= 15 (U <= 1,13V) -> after_hysteresis = 0 + if(adc_d >= 16) after_hysteresis <= 1'b1; // U >= 1,14V -> after_hysteresis = 1 + else if(adc_d < 8) after_hysteresis <= 1'b0; // U < 1,04V -> after_hysteresis = 0 + // Note: was >= 3,53V and <= 1,19V. The new trigger values allow more reliable detection of the first bit + // (it might not reach 3,53V due to the high time constant of the high pass filter in the analogue RF part). + // In addition, the new values are more in line with ISO14443-2: "The PICC shall detect the ”End of Pause” after the field exceeds + // 5% of H_INITIAL and before it exceeds 60% of H_INITIAL." Depending on the signal strength, 60% might well be less than 3,53V. - if(~(| adc_d[7:0])) // if adc_d == 0 (U <= 0,94V) - begin - if(deep_counter == 3'd7) // adc_d == 0 for 7 adc_clk ticks -> deep_modulation (by reader) - begin - deep_modulation <= 1'b1; - saw_deep_modulation <= 8'd0; - end - else - deep_counter <= deep_counter + 1; - end - else - begin - deep_counter <= 3'd0; - if(saw_deep_modulation == 8'd255) // adc_d != 0 for 255 adc_clk ticks -> deep_modulation is over, now waiting for tag's response - deep_modulation <= 1'b0; - else - saw_deep_modulation <= saw_deep_modulation + 1; - end - if(after_hysteresis) + // detecting a loss of reader's field (adc_d < 192 for 4096 clock cycles). If this is the case, + // set the detected reader signal (after_hysteresis) to '1' (unmodulated) + if(adc_d >= 192) begin has_been_low_for <= 12'd0; end @@ -74,120 +62,182 @@ begin if(has_been_low_for == 12'd4095) begin has_been_low_for <= 12'd0; - after_hysteresis <= 1'b1; // reset after_hysteresis to 1 if it had been 0 for 4096 cycles (no field) + after_hysteresis <= 1'b1; end else begin has_been_low_for <= has_been_low_for + 1; end end + end -// Report every 4 subcarrier cycles -// 128 periods of carrier frequency => 7-bit counter [negedge_cnt] -reg [6:0] negedge_cnt; -reg bit1, bit2, bit3, bit4; -reg curbit; - -// storage for four previous samples: -reg [7:0] adc_d_1; -reg [7:0] adc_d_2; -reg [7:0] adc_d_3; -reg [7:0] adc_d_4; +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// Reader -> PM3 +// detect when a reader is active (modulating). We assume that the reader is active, if we see the carrier off for at least 8 +// carrier cycles. We assume that the reader is inactive, if the carrier stayed high for at least 256 carrier cycles. +reg deep_modulation; +reg [2:0] deep_counter; +reg [8:0] saw_deep_modulation; -// the filtered signal (filter performs noise reduction and edge detection) -// (gaussian derivative) -wire signed [10:0] adc_d_filtered; -assign adc_d_filtered = (adc_d_4 << 1) + adc_d_3 - adc_d_1 - (adc_d << 1); +always @(negedge adc_clk) +begin + if(~(| adc_d[7:0])) // if adc_d == 0 (U <= 0,94V) + begin + if(deep_counter == 3'd7) // adc_d == 0 for 8 adc_clk ticks -> deep_modulation (by reader) + begin + deep_modulation <= 1'b1; + saw_deep_modulation <= 8'd0; + end + else + deep_counter <= deep_counter + 1; + end + else + begin + deep_counter <= 3'd0; + if(saw_deep_modulation == 8'd255) // adc_d != 0 for 256 adc_clk ticks -> deep_modulation is over, probably waiting for tag's response + deep_modulation <= 1'b0; + else + saw_deep_modulation <= saw_deep_modulation + 1; + end +end -// Registers to store steepest edges detected: -reg [7:0] rx_mod_falling_edge_max; -reg [7:0] rx_mod_rising_edge_max; -// A register to send 8 Bit results to the arm -reg [7:0] to_arm; +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// Tag -> PM3 +// filter the input for a tag's signal. The filter box needs the 4 previous input values and is a gaussian derivative filter +// for noise reduction and edge detection. +// store 4 previous samples: +reg [7:0] input_prev_4, input_prev_3, input_prev_2, input_prev_1; +// convert to signed signals (and multiply by two for samples at t-4 and t) +wire signed [10:0] input_prev_4_times_2 = {0, 0, input_prev_4, 0}; +wire signed [10:0] input_prev_3_times_1 = {0, 0, 0, input_prev_3}; +wire signed [10:0] input_prev_1_times_1 = {0, 0, 0, input_prev_1}; +wire signed [10:0] adc_d_times_2 = {0, 0, adc_d, 0}; -reg bit_to_arm; -reg fdt_indicator, fdt_elapsed; -reg [10:0] fdt_counter; -//reg [47:0] mod_sig_buf; -reg [31:0] mod_sig_buf; -//reg [5:0] mod_sig_ptr; -reg [4:0] mod_sig_ptr; -reg [3:0] mod_sig_flip; -reg mod_sig, mod_sig_coil; -reg temp_buffer_reset; -reg sendbit; -reg [3:0] sub_carrier_cnt; +wire signed [10:0] tmp_1, tmp_2; +wire signed [10:0] adc_d_filtered; +integer i; -// ADC data appears on the rising edge, so sample it on the falling edge +assign tmp_1 = input_prev_4_times_2 + input_prev_3_times_1; +assign tmp_2 = input_prev_1_times_1 + adc_d_times_2; + always @(negedge adc_clk) begin - // ------------------------------------------------------------------------------------------------------------------------------------------------------------------ - // relevant for TAGSIM_MOD only. Timing of Tag's answer relative to a command received from a reader - // ISO14443-3 specifies: - // fdt = 1172, if last bit was 0. - // fdt = 1236, if last bit was 1. - // the FPGA takes care for the 1172 delay. To achieve the additional 1236-1172=64 ticks delay, the ARM must send an additional correction bit (before the start bit). - // The correction bit will be coded as 00010000, i.e. it adds 4 bits to the transmission stream, causing the required delay. - if(fdt_counter == 11'd547) fdt_indicator <= 1'b1; // The ARM must not send earlier to prevent mod_sig_buf overflow. - // The mod_sig_buf can buffer 29 excess data bits, i.e. a maximum delay of 29 * 16 = 464 adc_clk ticks. fdt_indicator - // could appear at ssp_din after 1 tick, 16 ticks for the transfer, 128 ticks until response is sended. - // 1148 - 464 - 1 - 128 - 8 = 547 + // for (i = 3; i > 0; i = i - 1) + // begin + // input_shift[i] <= input_shift[i-1]; + // end + // input_shift[0] <= adc_d; + input_prev_4 <= input_prev_3; + input_prev_3 <= input_prev_2; + input_prev_2 <= input_prev_1; + input_prev_1 <= adc_d; +end + +// assign adc_d_filtered = (input_shift[3] << 1) + input_shift[2] - input_shift[0] - (adc_d << 1); +assign adc_d_filtered = tmp_1 - tmp_2; + - if ((mod_type == `TAGSIM_MOD) || (mod_type == `TAGSIM_LISTEN)) +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// internal FPGA timing. Maximum required period is 128 carrier clock cycles for a full 8 Bit transfer to ARM. (i.e. we need a +// 7 bit counter). Adjust its frequency to external reader's clock when simulating a tag or sniffing. +reg pre_after_hysteresis; +reg [3:0] reader_falling_edge_time; +reg [6:0] negedge_cnt; + +always @(negedge adc_clk) +begin + // detect a reader signal's falling edge and remember its timing: + pre_after_hysteresis <= after_hysteresis; + if (pre_after_hysteresis && ~after_hysteresis) + begin + reader_falling_edge_time[3:0] <= negedge_cnt[3:0]; + end + + // adjust internal timer counter if necessary: + if (negedge_cnt[3:0] == 4'd13 && (mod_type == `SNIFFER || mod_type == `TAGSIM_LISTEN) && deep_modulation) begin - if(fdt_counter == 11'd1148) // the RF part delays the rising edge by approx 5 adc_clk_ticks, the ADC needs 3 clk_ticks for A/D conversion, - // 16 ticks delay by mod_sig_buf - // 1172 - 5 - 3 - 16 = 1148. + if (reader_falling_edge_time == 4'd1) // reader signal changes right after sampling. Better sample earlier next time. begin - if(fdt_elapsed) - begin - if(negedge_cnt[3:0] == mod_sig_flip) mod_sig_coil <= mod_sig; // start modulating (if mod_sig is already set) - sub_carrier_cnt[3:0] <= sub_carrier_cnt[3:0] + 1; - end - else - begin - mod_sig_flip <= negedge_cnt[3:0]; // start modulation at this time - sub_carrier_cnt[3:0] <= 0; // subcarrier phase in sync with start of modulation - mod_sig_coil <= mod_sig; // assign signal to coil - fdt_elapsed = 1'b1; - if(~(| mod_sig_ptr[4:0])) mod_sig_ptr <= 5'd9; // if mod_sig_ptr == 0 -> didn't receive a 1 yet. Delay next 1 by n*128 ticks. - else temp_buffer_reset = 1'b1; // else fix the buffer size at current position - end + negedge_cnt <= negedge_cnt + 2; // time warp + end + else if (reader_falling_edge_time == 4'd0) // reader signal changes right before sampling. Better sample later next time. + begin + negedge_cnt <= negedge_cnt; // freeze time end else begin - fdt_counter <= fdt_counter + 1; // Count until 1155 + negedge_cnt <= negedge_cnt + 1; // Continue as usual end + reader_falling_edge_time[3:0] <= 4'd8; // adjust only once per detected edge end - else // other modes: don't use the delay line. + else if (negedge_cnt == 7'd127) // normal operation: count from 0 to 127 begin - mod_sig_coil <= ssp_dout; + negedge_cnt <= 0; end - - - //------------------------------------------------------------------------------------------------------------------------------------------- - // Relevant for READER_LISTEN only - // look for steepest falling and rising edges: + else + begin + negedge_cnt <= negedge_cnt + 1; + end +end + - if(negedge_cnt[3:0] == 4'd1) // reset modulation detector. Save current edge. +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// Tag -> PM3: +// determine best possible time for starting/resetting the modulation detector. +reg [3:0] mod_detect_reset_time; + +always @(negedge adc_clk) +begin + if (mod_type == `READER_LISTEN) + // (our) reader signal changes at t=1, tag response expected n*16+4 ticks later, further delayed by + // 3 ticks ADC conversion. + // 1 + 4 + 3 = 8 begin - if (adc_d_filtered > 0) - begin - rx_mod_falling_edge_max <= adc_d_filtered; - rx_mod_rising_edge_max <= 0; - end - else + mod_detect_reset_time <= 4'd8; + end + else + if (mod_type == `SNIFFER) + begin + // detect a rising edge of reader's signal and sync modulation detector to the tag's answer: + if (~pre_after_hysteresis && after_hysteresis && deep_modulation) + // reader signal rising edge detected at negedge_cnt[3:0]. This signal had been delayed + // 9 ticks by the RF part + 3 ticks by the A/D converter + 1 tick to assign to after_hysteresis. + // The tag will respond n*16 + 4 ticks later + 3 ticks A/D converter delay. + // - 9 - 3 - 1 + 4 + 3 = -6 begin - rx_mod_falling_edge_max <= 0; - rx_mod_rising_edge_max <= -adc_d_filtered; + mod_detect_reset_time <= negedge_cnt[3:0] - 4'd4; end end - else // detect modulation +end + + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// Tag -> PM3: +// modulation detector. Looks for the steepest falling and rising edges within a 16 clock period. If there is both a significant +// falling and rising edge (in any order), a modulation is detected. +reg signed [10:0] rx_mod_falling_edge_max; +reg signed [10:0] rx_mod_rising_edge_max; +reg curbit; + +always @(negedge adc_clk) +begin + if(negedge_cnt[3:0] == mod_detect_reset_time) + begin + // detect modulation signal: if modulating, there must have been a falling AND a rising edge + if (rx_mod_falling_edge_max > 5 && rx_mod_rising_edge_max > 5) + curbit <= 1'b1; // modulation + else + curbit <= 1'b0; // no modulation + // reset modulation detector + rx_mod_rising_edge_max <= 0; + rx_mod_falling_edge_max <= 0; + end + else // look for steepest edges (slopes) begin if (adc_d_filtered > 0) begin @@ -201,208 +251,309 @@ begin end end - // detect modulation signal: if modulating, there must be a falling and a rising edge - if (rx_mod_falling_edge_max > 6 && rx_mod_rising_edge_max > 6) - curbit <= 1'b1; // modulation - else - curbit <= 1'b0; // no modulation - - - // store previous samples for filtering and edge detection: - adc_d_4 <= adc_d_3; - adc_d_3 <= adc_d_2; - adc_d_2 <= adc_d_1; - adc_d_1 <= adc_d; +end + - // Relevant for TAGSIM_MOD only (timing the Tag's answer. See above) - // When we see end of a modulation and we are emulating a Tag, start fdt_counter. - // Reset fdt_counter when modulation is detected. - if(~after_hysteresis /* && mod_sig_buf_empty */ && mod_type == `TAGSIM_LISTEN) +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// Tag+Reader -> PM3 +// sample 4 bits reader data and 4 bits tag data for sniffing +reg [3:0] reader_data; +reg [3:0] tag_data; + +always @(negedge adc_clk) +begin + if(negedge_cnt[3:0] == 4'd0) begin - fdt_counter <= 11'd0; - fdt_elapsed = 1'b0; - fdt_indicator <= 1'b0; - temp_buffer_reset = 1'b0; - mod_sig_ptr <= 5'b00000; - mod_sig = 1'b0; - end + reader_data[3:0] <= {reader_data[2:0], after_hysteresis}; + tag_data[3:0] <= {tag_data[2:0], curbit}; + end +end - if(negedge_cnt[3:0] == 4'd1) + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// PM3 -> Tag: +// a delay line to ensure that we send the (emulated) tag's answer at the correct time according to ISO14443-3 +reg [31:0] mod_sig_buf; +reg [4:0] mod_sig_ptr; +reg mod_sig; + +always @(negedge adc_clk) +begin + if(negedge_cnt[3:0] == 4'd0) // sample data at rising edge of ssp_clk - ssp_dout changes at the falling edge. begin - // What do we communicate to the ARM - if(mod_type == `TAGSIM_LISTEN) - sendbit = after_hysteresis; - else if(mod_type == `TAGSIM_MOD) - /* if(fdt_counter > 11'd772) sendbit = mod_sig_coil; // huh? - else */ - sendbit = fdt_indicator; - else if (mod_type == `READER_LISTEN) - sendbit = curbit; + mod_sig_buf[31:2] <= mod_sig_buf[30:1]; // shift + if (~ssp_dout && ~mod_sig_buf[1]) + mod_sig_buf[1] <= 1'b0; // delete the correction bit (a single 1 preceded and succeeded by 0) else - sendbit = 1'b0; + mod_sig_buf[1] <= mod_sig_buf[0]; + mod_sig_buf[0] <= ssp_dout; // add new data to the delay line + + mod_sig = mod_sig_buf[mod_sig_ptr]; // the delayed signal. end +end - //------------------------------------------------------------------------------------------------------------------------------------------ - // Prepare 8 Bits to communicate to ARM - // in SNIFFER mode: 4 Bits data sniffed as Tag, 4 Bits data sniffed as Reader - if(mod_type == `SNIFFER) + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// PM3 -> Tag, internal timing: +// a timer for the 1172 cycles fdt (Frame Delay Time). Start the timer with a rising edge of the reader's signal. +// set fdt_elapsed when we no longer need to delay data. Set fdt_indicator when we can start sending data. +// Note: the FPGA only takes care for the 1172 delay. To achieve an additional 1236-1172=64 ticks delay, the ARM must send +// a correction bit (before the start bit). The correction bit will be coded as 00010000, i.e. it adds 4 bits to the +// transmission stream, causing the required additional delay. +reg [10:0] fdt_counter; +reg fdt_indicator, fdt_elapsed; +reg [3:0] mod_sig_flip; +reg [3:0] sub_carrier_cnt; + +// we want to achieve a delay of 1172. The RF part already has delayed the reader signals's rising edge +// by 9 ticks, the ADC took 3 ticks and there is always a delay of 32 ticks by the mod_sig_buf. Therefore need to +// count to 1172 - 9 - 3 - 32 = 1128 +`define FDT_COUNT 11'd1128 + +// The ARM must not send too early, otherwise the mod_sig_buf will overflow, therefore signal that we are ready +// with fdt_indicator. The mod_sig_buf can buffer 29 excess data bits, i.e. a maximum delay of 29 * 16 = 464 adc_clk ticks. +// fdt_indicator could appear at ssp_din after 1 tick, the transfer needs 16 ticks, the ARM can send 128 ticks later. +// 1128 - 464 - 1 - 128 - 8 = 535 +`define FDT_INDICATOR_COUNT 11'd535 + +// reset on a pause in listen mode. I.e. the counter starts when the pause is over: +assign fdt_reset = ~after_hysteresis && mod_type == `TAGSIM_LISTEN; + +always @(negedge adc_clk) +begin + if (fdt_reset) begin - if (negedge_cnt == 7'd63) - begin - if(deep_modulation) // a reader is sending (or there's no field at all) + fdt_counter <= 11'd0; + fdt_elapsed <= 1'b0; + fdt_indicator <= 1'b0; + end + else + begin + if(fdt_counter == `FDT_COUNT) + begin + if(~fdt_elapsed) // just reached fdt. begin - to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis_prev4,1'b0,1'b0,1'b0,1'b0}; + mod_sig_flip <= negedge_cnt[3:0]; // start modulation at this time + sub_carrier_cnt <= 4'd0; // subcarrier phase in sync with start of modulation + fdt_elapsed <= 1'b1; end else begin - to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis_prev4,bit1,bit2,bit3,bit4}; - end - negedge_cnt <= 0; - end + sub_carrier_cnt <= sub_carrier_cnt + 1; + end + end else begin - negedge_cnt <= negedge_cnt + 1; + fdt_counter <= fdt_counter + 1; end end - else - // other modes: 8 Bits info on queue delay + + if(fdt_counter == `FDT_INDICATOR_COUNT) fdt_indicator <= 1'b1; +end + + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// PM3 -> Reader or Tag +// assign a modulation signal to the antenna. This signal is either a delayed signal (to achieve fdt when sending to a reader) +// or undelayed when sending to a tag +reg mod_sig_coil; + +always @(negedge adc_clk) +begin + if (mod_type == `TAGSIM_MOD) // need to take care of proper fdt timing begin - if(negedge_cnt == 7'd127) + if(fdt_counter == `FDT_COUNT) begin - if (mod_type == `TAGSIM_MOD) + if(fdt_elapsed) begin - to_arm[7:0] <= {mod_sig_ptr[4:0], mod_sig_flip[3:1]}; + if(negedge_cnt[3:0] == mod_sig_flip) mod_sig_coil <= mod_sig; end else begin - to_arm[7:0] <= 8'd0; + mod_sig_coil <= mod_sig; // just reached fdt. Immediately assign signal to coil end - negedge_cnt <= 0; end - else - begin - negedge_cnt <= negedge_cnt + 1; - end - end - - if(negedge_cnt == 7'd1) - begin - after_hysteresis_prev1 <= after_hysteresis; - bit1 <= curbit; end - if(negedge_cnt == 7'd17) + else // other modes: don't delay begin - after_hysteresis_prev2 <= after_hysteresis; - bit2 <= curbit; - end - if(negedge_cnt == 7'd33) + mod_sig_coil <= ssp_dout; + end +end + + + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// PM3 -> Reader +// determine the required delay in the mod_sig_buf (set mod_sig_ptr). +reg temp_buffer_reset; + +always @(negedge adc_clk) +begin + if(fdt_reset) begin - after_hysteresis_prev3 <= after_hysteresis; - bit3 <= curbit; - end - if(negedge_cnt == 7'd47) + mod_sig_ptr <= 5'd0; + temp_buffer_reset = 1'b0; + end + else begin - after_hysteresis_prev4 <= after_hysteresis; - bit4 <= curbit; + if(fdt_counter == `FDT_COUNT && ~fdt_elapsed) // if we just reached fdt + if(~(| mod_sig_ptr[4:0])) + mod_sig_ptr <= 5'd8; // ... but didn't buffer a 1 yet, delay next 1 by n*128 ticks. + else + temp_buffer_reset = 1'b1; // else no need for further delays. + + if(negedge_cnt[3:0] == 4'd0) // at rising edge of ssp_clk - ssp_dout changes at the falling edge. + begin + if((ssp_dout || (| mod_sig_ptr[4:0])) && ~fdt_elapsed) // buffer a 1 (and all subsequent data) until fdt is reached. + if (mod_sig_ptr == 5'd31) + mod_sig_ptr <= 5'd0; // buffer overflow - data loss. + else + mod_sig_ptr <= mod_sig_ptr + 1; // increase buffer (= increase delay by 16 adc_clk ticks). mod_sig_ptr always points ahead of first 1. + else if(fdt_elapsed && ~temp_buffer_reset) + begin + // wait for the next 1 after fdt_elapsed before fixing the delay and starting modulation. This ensures that the response can only happen + // at intervals of 8 * 16 = 128 adc_clk ticks (as defined in ISO14443-3) + if(ssp_dout) + temp_buffer_reset = 1'b1; + if(mod_sig_ptr == 5'd1) + mod_sig_ptr <= 5'd8; // still nothing received, need to go for the next interval + else + mod_sig_ptr <= mod_sig_ptr - 1; // decrease buffer. + end + end end - - //-------------------------------------------------------------------------------------------------------------------------------------------------------------- - // Relevant in TAGSIM_MOD only. Delay-Line to buffer data and send it at the correct time - if(negedge_cnt[3:0] == 4'd0) // at rising edge of ssp_clk - ssp_dout changes at the falling edge. +end + + + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// FPGA -> ARM communication: +// buffer 8 bits data to be sent to ARM. Shift them out bit by bit. +reg [7:0] to_arm; + +always @(negedge adc_clk) +begin + if (negedge_cnt[5:0] == 6'd63) // fill the buffer begin - mod_sig_buf[31:0] <= {mod_sig_buf[30:1], ssp_dout, 1'b0}; // shift in new data starting at mod_sig_buf[1]. mod_sig_buf[0] = 0 always. - // asign the delayed signal to mod_sig, but don't modulate with the correction bit (which is sent as 00010000, all other bits will come with at least 2 consecutive 1s) - // side effect: when ptr = 1 it will cancel the first 1 of every block of ones. Note: this would only be the case if we received a 1 just before fdt_elapsed. - if((ssp_dout || (| mod_sig_ptr[4:0])) && ~fdt_elapsed) // buffer a 1 (and all subsequent data) until fdt_counter = 1148 adc_clk ticks. - //if(mod_sig_ptr == 6'b101110) // buffer overflow at 46 - this would mean data loss - //begin - // mod_sig_ptr <= 6'b000000; - //end - if (mod_sig_ptr == 5'd30) mod_sig_ptr <= 5'd0; - else mod_sig_ptr <= mod_sig_ptr + 1; // increase buffer (= increase delay by 16 adc_clk ticks). ptr always points to first 1. - else if(fdt_elapsed && ~temp_buffer_reset) - // fdt_elapsed. If we didn't receive a 1 yet, ptr will be at 9 and not yet fixed. Otherwise temp_buffer_reset will be 1 already. + if (mod_type == `SNIFFER) begin - // wait for the next 1 after fdt_elapsed before fixing the delay and starting modulation. This ensures that the response can only happen - // at intervals of 8 * 16 = 128 adc_clk ticks intervals (as defined in ISO14443-3) - if(ssp_dout) temp_buffer_reset = 1'b1; - if(mod_sig_ptr == 5'd2) mod_sig_ptr <= 5'd9; // still nothing received, need to go for the next interval - else mod_sig_ptr <= mod_sig_ptr - 1; // decrease buffer. + if(deep_modulation) // a reader is sending (or there's no field at all) + begin + to_arm <= {reader_data[3:0], 4'b0000}; // don't send tag data + end + else + begin + to_arm <= {reader_data[3:0], tag_data[3:0]}; + end end else begin - if(~mod_sig_buf[mod_sig_ptr-1] && ~mod_sig_buf[mod_sig_ptr+1]) mod_sig = 1'b0; - // finally, assign the delayed signal: - else mod_sig = mod_sig_buf[mod_sig_ptr]; + to_arm[7:0] <= {mod_sig_ptr[4:0], mod_sig_flip[3:1]}; // feedback timing information + end + end + + if(negedge_cnt[2:0] == 3'b000 && mod_type == `SNIFFER) // shift at double speed + begin + // Don't shift if we just loaded new data, obviously. + if(negedge_cnt[5:0] != 6'd0) + begin + to_arm[7:1] <= to_arm[6:0]; + end + end + + if(negedge_cnt[3:0] == 4'b0000 && mod_type != `SNIFFER) + begin + // Don't shift if we just loaded new data, obviously. + if(negedge_cnt[6:0] != 7'd0) + begin + to_arm[7:1] <= to_arm[6:0]; end end - //----------------------------------------------------------------------------------------------------------------------------------------------------------------------- - // Communication to ARM (SSP Clock and data) - // SNIFFER mode (ssp_clk = adc_clk / 8, ssp_frame clock = adc_clk / 64)): +end + + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// FPGA -> ARM communication: +// generate a ssp clock and ssp frame signal for the synchronous transfer from/to the ARM +reg ssp_clk; +reg ssp_frame; +reg [2:0] ssp_frame_counter; + +always @(negedge adc_clk) +begin if(mod_type == `SNIFFER) + // SNIFFER mode (ssp_clk = adc_clk / 8, ssp_frame clock = adc_clk / 64)): begin - if(negedge_cnt[2:0] == 3'b100) - ssp_clk <= 1'b0; - - if(negedge_cnt[2:0] == 3'b000) - begin + if(negedge_cnt[2:0] == 3'd0) ssp_clk <= 1'b1; - // Don't shift if we just loaded new data, obviously. - if(negedge_cnt[5:0] != 6'd0) - begin - to_arm[7:1] <= to_arm[6:0]; - end - end + if(negedge_cnt[2:0] == 3'd4) + ssp_clk <= 1'b0; - if(negedge_cnt[5:4] == 2'b00) - ssp_frame = 1'b1; - else - ssp_frame = 1'b0; - - bit_to_arm = to_arm[7]; + if(negedge_cnt[5:0] == 6'd0) // ssp_frame rising edge indicates start of frame + ssp_frame <= 1'b1; + if(negedge_cnt[5:0] == 6'd8) + ssp_frame <= 1'b0; end else - //----------------------------------------------------------------------------------------------------------------------------------------------------------------------- - // Communication to ARM (SSP Clock and data) // all other modes (ssp_clk = adc_clk / 16, ssp_frame clock = adc_clk / 128): begin - if(negedge_cnt[3:0] == 4'b1000) ssp_clk <= 1'b0; + if(negedge_cnt[3:0] == 4'd0) + ssp_clk <= 1'b1; + if(negedge_cnt[3:0] == 4'd8) + ssp_clk <= 1'b0; - if(negedge_cnt[3:0] == 4'b0111) - begin - // if(ssp_frame_counter == 3'd7) ssp_frame_counter <= 3'd0; - // else ssp_frame_counter <= ssp_frame_counter + 1; - if (negedge_cnt[6:4] == 3'b000) ssp_frame = 1'b1; - else ssp_frame = 1'b0; - end - // ssp_frame = (ssp_frame_counter == 3'd7); + if(negedge_cnt[6:0] == 7'd7) // ssp_frame rising edge indicates start of frame + ssp_frame <= 1'b1; + if(negedge_cnt[6:0] == 7'd23) + ssp_frame <= 1'b0; + end +end - if(negedge_cnt[3:0] == 4'b0000) - begin - ssp_clk <= 1'b1; - // Don't shift if we just loaded new data, obviously. - if(negedge_cnt[6:0] != 7'd0) - begin - to_arm[7:1] <= to_arm[6:0]; - end - end - - if (mod_type == `TAGSIM_MOD && fdt_elapsed && temp_buffer_reset) - // transmit timing information - bit_to_arm = to_arm[7]; + + +//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// +// FPGA -> ARM communication: +// select the data to be sent to ARM +reg bit_to_arm; +reg sendbit; + +always @(negedge adc_clk) +begin + if(negedge_cnt[3:0] == 4'd0) + begin + // What do we communicate to the ARM + if(mod_type == `TAGSIM_LISTEN) + sendbit = after_hysteresis; + else if(mod_type == `TAGSIM_MOD) + /* if(fdt_counter > 11'd772) sendbit = mod_sig_coil; // huh? + else */ + sendbit = fdt_indicator; + else if (mod_type == `READER_LISTEN) + sendbit = curbit; else - // transmit data or fdt_indicator - bit_to_arm = sendbit; - end - -end //always @(negedge adc_clk) + sendbit = 1'b0; + end -assign ssp_din = bit_to_arm; + if(mod_type == `SNIFFER) + // send sampled reader and tag data: + bit_to_arm = to_arm[7]; + else if (mod_type == `TAGSIM_MOD && fdt_elapsed && temp_buffer_reset) + // send timing information: + bit_to_arm = to_arm[7]; + else + // send data or fdt_indicator + bit_to_arm = sendbit; +end + + + + +assign ssp_din = bit_to_arm; // Subcarrier (adc_clk/16, for TAGSIM_MOD only). wire sub_carrier;