Hi
Ian: that was also partly what we figured out, so thanks for confirming.
But maybe someone can help clarify the start flow at a specific vita time from
fpga-source.
The "set_stb" generated in "radio_ctrl_proc.v", seems to depend on "vita_time"
equal "trigger_time" ie. "now" in case "HAS_TIME". "set_stb" is used to latch
in setting registers. Now in "new_rx_control.v", "command_valid" depends on
"store_command" which is changed after "set_stb" on "sr_time_l". This implies
that in the below "ibs_state" state "IBS_RUNNING" is achieved at "now", but
since this must be true some clk's after "set_stb", I see a kind of problematic
discrepancy between the "now" in "radio_ctrl_proc.v" and "new_rx_control.v". I
simple cant understand that they both can be now=true when "HAS_TIME" ?!?!?!
I must admit that the flow works (up to constant latency), but maybe the flow
is always without HAS_TIME ???
case (ibs_state)
IBS_IDLE : begin
clear_halt <= 1'b0; // Incase we got here through a
HALT.
if (command_valid)
// There is a valid command to pop from FIFO.
if (stop)
begin
// Stop bit set in this command, go
idle.
ibs_state <= IBS_IDLE;//IBS_ZEROLEN;
end
else if (late & ~send_imm)
begin
// Got this command later than its
execution time.
ibs_state <= IBS_LATECMD;
end
else if (now | send_imm)
begin
// Either its time to run this command
or it should run immediately without a time.
ibs_state <= IBS_RUNNING;
lines_left <= numlines;
repeat_lines <= numlines;
chain_sav <= chain;
reload_sav <= reload;
end
end // case: IBS_IDLE
_____________________________________________________________
"radio_ctrl_proc.v":
time_compare time_compare (.clk(clk), .reset(reset), .time_now(vita_time),
.trigger_time(ctrl_tdata), .now(now), .early(), .late(late), .too_early());
assign go = now | late;
assign set_stb = (rc_state == RC_DATA) & ready & ctrl_tvalid;
And further:
case(rc_state)
RC_HEAD :
if(ctrl_tvalid)
begin
sid <= ctrl_tdata[31:0];
seqnum <= ctrl_tdata[59:48];
HAS_TIME_reg <= HAS_TIME;
if(IS_EC)
if(HAS_TIME)
rc_state <= RC_TIME;
else
rc_state <= RC_DATA;
else
if(~ctrl_tlast)
rc_state <= RC_DUMP;
end
RC_TIME :
if(ctrl_tvalid)
if(ctrl_tlast)
rc_state <= RC_RESP_HEAD;
else if(go)
rc_state <= RC_DATA;
_____________________________________________________________
/fabric
-----Oprindelig meddelelse-----
Fra: USRP-users <usrp-users-boun...@lists.ettus.com> På vegne af Ian Buckley
via USRP-users
Sendt: Wednesday, 23 May 2018 20.11
Til: kf <k...@chora.dk>
Cc: usrp-users@lists.ettus.com
Emne: Re: [USRP-users] B210 initial tickcount offset
There is a certain amount of (deterministic) latency incurred in the pipelining
of H/W signals, both data and control.
The tick count applied to the data will be accurate w.r.t the instant the data
left the DDC and was packetized.
-Ian
> On May 23, 2018, at 2:26 AM, kf via USRP-users <usrp-users@lists.ettus.com>
> wrote:
>
> Hi.
>
> I am having trouble understanding why the first samples I receive have
> a tick count offset of 7.
>
> My setup is:
> - B210 with gpsdo
> - Time source and reference set to 'gspdo'
> - Two-channel RX
> - Sample rate set to 16Mhz
>
> The procedure is then to
> - Reset to time to 0 using the PPS signal
> - Requesting streaming to begin on time 2
> - The first samples received has a tick of 32000007, but it should
> have been 32000000 (time 2)
>
> Why is the tick count 32000007 on the initially received samples?
>
> It seems very consistent, as the received tick count is the same on
> three different B210 boards handled by three different PCs.
>
> Below is the relevant code parts mentioned above.
>
> Regards
> /KF
>
>
> === Code for resetting time to 0 ===
>
> const uhd::time_spec_t last_pps_time1 = usrp->get_time_last_pps();
> while (last_pps_time1 == usrp->get_time_last_pps())
> boost::this_thread::sleep(boost::posix_time::milliseconds(50));
> usrp->set_time_next_pps(uhd::time_spec_t(0.0));
> const uhd::time_spec_t last_pps_time2 = usrp->get_time_last_pps();
> while (last_pps_time2 == usrp->get_time_last_pps())
> boost::this_thread::sleep(boost::posix_time::milliseconds(50));
>
>
> === Code for streaming ===
>
> double seconds = 2.0;
> std::cout << "Issuing stream command to start streaming at time " <<
> seconds << std::endl; uhd::stream_cmd_t
> stream_cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
> stream_cmd.num_samps = 0;
> stream_cmd.stream_now = false;
> stream_cmd.time_spec = uhd::time_spec_t(seconds);
> rx_stream->issue_stream_cmd(stream_cmd);
>
>
> === Printing the first tick received ===
>
> size_t num_rx_samps = rx_stream->recv(buffers,
> _startArguments.samplesPerBuffer, md, 10.0, false); std::cout <<
> "Received first samples. Tick: " <<
> md.time_spec.to_ticks(16000000) << std::endl;
>
>
>
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