// Satsuoni, October 2017, Added FeliCa support
//
//this code demodulates and modulates signal as described in ISO/IEC 18092. That includes packets used for Felica, NFC Tag 3, etc. (which do overlap)
//simple envelope following algorithm is used (modification of fail0verflow LF one) is used to combat some nasty aliasing effect with testing phone (envelope looked like sine wave)
// only 212 kbps (fc/64) for now 414 is relatively straightforward...
// modulation waits for
//market sprocket -doesn't really mean anything ;)
`define SNIFFER 3'b000
`define TAGSIM_LISTEN 3'b001 //same as SNIFFER, really. demod does not distinguish tag from reader
`define TAGSIM_MODULATE 3'b010
`define TAGSIM_MOD_NODELAY 3'b011 //not implemented yet. for use with commands other than polling, which might require different timing, as per Felica standard
module hi_flite(
pck0, ck_1356meg, ck_1356megb,
pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
adc_d, adc_clk,
ssp_frame, ssp_din, ssp_dout, ssp_clk,
cross_hi, cross_lo,
dbg,
mod_type // maybe used
);
input pck0, ck_1356meg, ck_1356megb;
output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
input [7:0] adc_d;
output adc_clk;
input ssp_dout;
output ssp_frame, ssp_din, ssp_clk;
input cross_hi, cross_lo;
output dbg;
input [2:0] mod_type; // maybe used.
assign dbg=0;
// Most off, oe4 for modulation; No reader emulation (would presumably just require switching power on, but I am not sure)
assign pwr_hi = 1'b0;
assign pwr_lo = 1'b0;
assign pwr_oe1 = 1'b0;
assign pwr_oe2 = 1'b0;
assign pwr_oe3 = 1'b0;
//512x64/fc -wait before ts0, 32768 ticks
//tslot: 256*64/fc
assign adc_clk = ck_1356meg;
///heuristic values for initial thresholds. seem to work OK
`define imin 70//(13'd256)
`define imax 180//(-13'd256)
`define ithrmin 91//-13'd8
`define ithrmax 160// 13'd8
//minimum values and corresponding thresholds
reg [8:0] curmin=`imin;
reg [8:0] curminthres=`ithrmin;
reg [8:0] curmaxthres=`ithrmax;
reg [8:0] curmax=`imax;
//signal state, 1-not modulated, 0 -modulated
reg after_hysteresis = 1'b1;
//state machine for envelope tracking
reg [1:0] state=1'd0;
//lower edge detected, trying to detect first bit of SYNC (b24d, 1011001001001101)
reg try_sync=1'b0;
//detected first sync bit, phase frozen
reg did_sync=0;
`define bithalf_212 32 //half-bit length for 212 kbit
`define bitlen_212 64 //full-bit length for 212 kbit
`define bitmlen_212 63 //bit transition edge
`define bitmhalf_212 31 //mod flip
//ssp clock and current values
reg ssp_clk;
reg ssp_frame;
reg curbit=1'b0;
reg [7:0] fccount=8'd0; // in-bit tick counter. Counts carrier cycles from the first lower edge detected, reset on every manchester bit detected
reg [7:0] tsinceedge=8'd0;// ticks from last edge, desync if the valye is too large
reg zero=1'b0; // Manchester first halfbit low second high corresponds to this value. It has been known to change. SYNC is used to set it
//ssp counter for transfer and framing
reg [8:0] ssp_cnt=9'd0;
always @(posedge adc_clk)
ssp_cnt <= (ssp_cnt + 1);
reg getting_arm_data=1'b0;
reg [47:0] delayline=48'd0; //48-bit preamble delay line. Just push the data into it starting from first SYNC (1) bit coming from ARM Made this long to keep all ARM data received during preamble
reg [5:0] delay_read_ptr=6'd0; // this is supposed to count ARM delay in the buffer.
reg preamble=0; // whether we are sending preamble
always @(negedge adc_clk)
begin
//count fc/64 - transfer bits to ARM at the rate they are received
if(ssp_cnt[5:0] == 6'b000000)
begin
ssp_clk <= 1'b1;
ssp_din <= curbit;
//sample ssp_dout?
if(mod_type==`TAGSIM_MODULATE||mod_type==`TAGSIM_MOD_NODELAY)
begin
delayline<={delayline[46:0],ssp_dout};
if ((~getting_arm_data) && ssp_dout)
begin
getting_arm_data <=1'b1;
delay_read_ptr<=delay_read_ptr+1;
end
else
begin
if (getting_arm_data & preamble)
begin
delay_read_ptr<=delay_read_ptr+1;
end
end
end
else
begin
getting_arm_data <=1'b0;
delay_read_ptr<=6'd0;
end
end
if(ssp_cnt[5:0] == 6'b100000)
ssp_clk <= 1'b0;
//create frame pulses. TBH, I still don't know what they do exactly, but they are crucial for ARM->FPGA transfer. If the frame is in the beginning of the byte, transfer slows to a crawl for some reason
// took me a day to figure THAT out.
if(ssp_cnt[8:0] == 9'd31)
begin
ssp_frame <= 1'b1;
end
if(ssp_cnt[8:0] == 9'b1011111)
begin
ssp_frame <= 1'b0;
end
end
//send current bit (detected in SNIFF mode or the one being modulated in MOD mode, 0 otherwise)
reg ssp_din;
//previous signal value, mostly to detect SYNC
reg prv =1'b1;
reg[7:0] mid=8'd128; //for simple error correction in mod/demod detection, use maximum of modded/demodded in given interval. Maybe 1 bit is extra? but better safe than sorry.
//modulated coil. set to 1 to modulate low, 0 to keep signal high
reg mod_sig_coil=1'b0;
// set TAGSIM__MODULATE on ARM if we want to write... (frame would get lost if done mid-frame...)
// start sending over 1s on ssp->arm when we start sending preamble
reg counting_desync=1'b0; // are we counting bits since last frame?
reg sending=1'b0; // are we actively modulating?
reg [11:0] bit_counts=12'd0;///for timeslots... only support ts=0 for now, at 212 speed -512 fullbits from end of frame. One hopes.
always @(negedge adc_clk) //every data ping?
begin
//envelope follow code...
////////////
if ((mod_type==`SNIFFER )||(mod_type==`TAGSIM_LISTEN))
begin
if (adc_d>curmaxthres) //rising edge
begin
case (state)
0: begin
curmax <= adc_d>155? adc_d :155;
state <= 2;
end
1: begin
curminthres <= ( (curmin>>1)+(curmin>>2)+(curmin>>4)+(curmax>>3)+(curmax>>4)); //threshold: 0.1875 max + 0.8125 min
curmaxthres <= ( (curmax>>1)+(curmax>>2)+(curmax>>4)+(curmin>>3)+(curmin>>4));
curmax <= adc_d>155? adc_d :155; // to hopefully prevent overflow from spikes going up to 255
state <= 2;
end
2: begin
if (adc_d>curmax)
curmax <= adc_d;
end
default:
begin
end
endcase
after_hysteresis <=1'b1;
if(try_sync)
tsinceedge<=0;
end
else if (adc_d<curminthres) //falling edge
begin
case (state)
0: begin
curmin <=adc_d<96? adc_d :96;
state <=1;
end
1: begin
if (adc_d<curmin)
curmin <= adc_d;
end
2: begin
curminthres <= ( (curmin>>1)+(curmin>>2)+(curmin>>4)+(curmax>>3)+(curmax>>4));
curmaxthres <= ( (curmax>>1)+(curmax>>2)+(curmax>>4)+(curmin>>3)+(curmin>>4));
curmin <=adc_d<96? adc_d :96;
state <=1;
end
default:
begin
end
endcase
after_hysteresis <=0;
if (~try_sync ) //begin modulation, lower edge...
begin
try_sync <=1;
counting_desync<=1'b0;
fccount <= 1;
did_sync<=0;
curbit<=0;
mid <=8'd127;
tsinceedge<=0;
prv <=1;
end
else
begin
tsinceedge<=0;
end
end
else //stable state, low or high
begin
curminthres <= ( (curmin>>1)+(curmin>>2)+(curmin>>4)+(curmax>>3)+(curmax>>4));
curmaxthres <= ( (curmax>>1)+(curmax>>2)+(curmax>>4)+(curmin>>3)+(curmin>>4));
state <=0;
if (try_sync )
begin
if (tsinceedge>=(128))
begin
//we might need to start counting... assuming ARM wants to reply to the frame.
counting_desync<=1'b1;
bit_counts<=1;// i think? 128 is about 2 bits passed... but 1 also works
try_sync<=0;
did_sync<=0;//desync
curmin <=`imin; //reset envelope
curmax <=`imax;
curminthres <=`ithrmin;
curmaxthres <=`ithrmax;
prv <=1;
tsinceedge <=0;
after_hysteresis <=1'b1;
curbit <=0;
mid <=8'd128;
end
else
tsinceedge<=(tsinceedge+1);
end
end
//move the counter to the outside...
if (adc_d>=curminthres||try_sync)
if(fccount==`bitmlen_212)
begin
fccount<=0;
if (counting_desync)
begin
if(bit_counts>768) // should be over ts0 now, without ARM interference... stop counting...
begin
bit_counts<=0;
counting_desync<=0;
end
else
bit_counts<=bit_counts+1;
end
end
else
begin
fccount<=fccount+1;
end
if (try_sync && tsinceedge<128)
begin
//detect bits in their middle ssp sampling is in sync, so it would sample all bits in order
if (fccount==`bithalf_212)
begin
if ((~did_sync) && ((prv==1&&(mid>128))||(prv==0&&(mid<=128))))
begin
//sync the Zero, and set curbit roperly
did_sync <=1'b1;
zero <= ~prv;// 1-prv
curbit <=1;
end
else
curbit <= (mid>128) ? (~zero):zero;
prv <=(mid>128) ?1:0;
if(adc_d>curmaxthres)
mid <=8'd129;
else if (adc_d<curminthres)
mid <=8'd127;
else
begin
if (after_hysteresis)
begin
mid <=8'd129;
end
else
begin
mid<=8'd127;
end
end
end
else
begin
if (fccount==`bitmlen_212)
begin
// fccount <=0;
prv <=(mid>128)?1:0;
mid <=128;
end
else
begin
// minimum-maximum calc
if(adc_d>curmaxthres)
mid <=mid+1;
else if (adc_d<curminthres)
mid <=mid-1;
else
begin
if (after_hysteresis)
begin
mid <=mid+1;
end
else
begin
mid<=mid-1;
end
end
end
end
end
else
begin
end
sending <=0;
end //listen mode end
else
begin //sim mode start
//not sure how precise do the time slots have to be... is anything within Ts ok?
//keep counting until 576, just in case
if(fccount==`bitmlen_212)
begin
if (bit_counts==512) //
curbit<=1;
else
begin
if(bit_counts>512)
curbit<=mod_sig_coil;//delayline[delay_read_ptr];//bit_counts[0];
else
curbit<=0;
end
fccount<=0;
if (bit_counts<=576) //we don't need to count after that...
begin
bit_counts<=bit_counts+1;
if (bit_counts== 512) //should start sending from next tick... i think?
begin
sending <=1;
mod_sig_coil <=1;//modulate... down?
preamble<=1;
end
else
if (bit_counts== 559)
begin
preamble<=0;
end
end
if (sending)
begin //need next bit
if(preamble)
mod_sig_coil<=1;
else
mod_sig_coil<=~delayline[delay_read_ptr];
end
end
else
begin
fccount<=fccount+1;
if ((fccount==`bitmhalf_212)&&(sending)) //flip modulation mid-bit
begin
mod_sig_coil<=~mod_sig_coil;//flip
end
end
end //sim mode end
end
assign pwr_oe4 = mod_sig_coil & (mod_type == `TAGSIM_MODULATE)&sending;
endmodule