module chan_fifo_reader
( reset, tx_clock, tx_strobe, adc_time, samples_format,
fifodata, pkt_waiting, rdreq, skip, tx_q, tx_i,
underrun, tx_empty, debug, rssi, threshhold, rssi_wait) ;
input wire reset ;
input wire tx_clock ;
input wire tx_strobe ; //signal to output tx_i and tx_q
input wire [31:0] adc_time ; //current time
input wire [3:0] samples_format ;// not useful at this point
input wire [31:0] fifodata ; //the data input
input wire pkt_waiting ; //signal the next packet is ready
output reg rdreq ; //actually an ack to the current fifodata
output reg skip ; //finish reading current packet
output reg [15:0] tx_q ; //top 16 bit output of fifodata
output reg [15:0] tx_i ; //bottom 16 bit output of fifodata
output reg underrun ;
output reg tx_empty ; //cause 0 to be the output
input wire [31:0] rssi;
input wire [31:0] threshhold;
input wire [31:0] rssi_wait;
output wire [14:0] debug;
assign debug = {reader_state, trash, skip, timestamp[4:0], adc_time[4:0]};
// Should not be needed if adc clock rate < tx clock rate
// Used only to debug
`define JITTER 5
//Samples format
// 16 bits interleaved complex samples
`define QI16 4'b0
// States
parameter IDLE = 3'd0;
parameter HEADER = 3'd1;
parameter TIMESTAMP = 3'd2;
parameter WAIT = 3'd3;
parameter WAITSTROBE = 3'd4;
parameter SEND = 3'd5;
// Header format
`define PAYLOAD 8:2
`define ENDOFBURST 27
`define STARTOFBURST 28
`define RSSI_FLAG 26
/* State registers */
reg [2:0] reader_state;
/* Local registers */
reg [6:0] payload_len;
reg [6:0] read_len;
reg [31:0] timestamp;
reg burst;
reg trash;
reg rssi_flag;
reg [31:0] time_wait;
always @(posedge tx_clock)
begin
if (reset)
begin
reader_state <= IDLE;
rdreq <= 0;
skip <= 0;
underrun <= 0;
burst <= 0;
tx_empty <= 1;
tx_q <= 0;
tx_i <= 0;
trash <= 0;
rssi_flag <= 0;
time_wait <= 0;
end
else
begin
case (reader_state)
IDLE:
begin
/*
* reset all the variables and wait for a tx_strobe
* it is assumed that the ram connected to this fifo_reader
* is a short hand fifo meaning that the header to the next packet
* is already available to this fifo_reader when pkt_waiting is on
*/
skip <=0;
time_wait <= 0;
if (pkt_waiting == 1)
begin
reader_state <= HEADER;
rdreq <= 1;
underrun <= 0;
end
if (burst == 1 && pkt_waiting == 0)
underrun <= 1;
if (tx_strobe == 1)
tx_empty <= 1 ;
end
/* Process header */
HEADER:
begin
if (tx_strobe == 1)
tx_empty <= 1 ;
rssi_flag <= fifodata[`RSSI_FLAG]&fifodata[`STARTOFBURST];
//Check Start/End burst flag
if (fifodata[`STARTOFBURST] == 1
&& fifodata[`ENDOFBURST] == 1)
burst <= 0;
else if (fifodata[`STARTOFBURST] == 1)
burst <= 1;
else if (fifodata[`ENDOFBURST] == 1)
burst <= 0;
if (trash == 1 && fifodata[`STARTOFBURST] == 0)
begin
skip <= 1;
reader_state <= IDLE;
rdreq <= 0;
end
else
begin
payload_len <= fifodata[`PAYLOAD] ;
read_len <= 0;
rdreq <= 1;
reader_state <= TIMESTAMP;
end
end
TIMESTAMP:
begin
timestamp <= fifodata;
reader_state <= WAIT;
if (tx_strobe == 1)
tx_empty <= 1 ;
rdreq <= 0;
end
// Decide if we wait, send or discard samples
WAIT:
begin
if (tx_strobe == 1)
tx_empty <= 1 ;
time_wait <= time_wait + 32'd1;
// Outdated
if ((timestamp < adc_time) ||
(time_wait >= rssi_wait && rssi_wait != 0 && rssi_flag))
begin
trash <= 1;
reader_state <= IDLE;
skip <= 1;
end
// Let's send it
else if ((timestamp <= adc_time + `JITTER
&& timestamp > adc_time)
|| timestamp == 32'hFFFFFFFF)
begin
if (rssi <= threshhold || rssi_flag == 0)
begin
trash <= 0;
reader_state <= WAITSTROBE;
end
else
reader_state <= WAIT;
end
else
reader_state <= WAIT;
// Wait a little bit more
//else if (timestamp > adc_time + `JITTER)
// reader_state <= WAIT;
end
// Wait for the transmit chain to be ready
WAITSTROBE:
begin
// If end of payload...
if (read_len == payload_len)
begin
reader_state <= IDLE;
skip <= 1;
if (tx_strobe == 1)
tx_empty <= 1 ;
end
else if (tx_strobe == 1)
begin
reader_state <= SEND;
rdreq <= 1;
end
end
// Send the samples to the tx_chain
SEND:
begin
reader_state <= WAITSTROBE;
read_len <= read_len + 7'd1;
tx_empty <= 0;
rdreq <= 0;
case(samples_format)
`QI16:
begin
tx_i <= fifodata[15:0];
tx_q <= fifodata[31:16];
end
// Assume 16 bits complex samples by default
default:
begin
tx_i <= fifodata[15:0];
tx_q <= fifodata[31:16];
end
endcase
end
default:
begin
//error handling
reader_state <= IDLE;
end
endcase
end
end
endmodule