5.7 ndigo6g12_tdc.cpp

#include <stdio.h>
#include "ndigo6g12_app.h"

void Ndigo6GApp::ProcessTDCPacket(crono_packet* pkt) {
	// TDC packet timestamp relates to end of packet
	// adjust for timespan covered
	double packetTs =
		(double)(pkt->timestamp - pi->tdc_packet_timestamp_offset);

	// calculate packet timestamp in picoseconds
	packetTs *= pi->packet_ts_period;

	// packet length is number of 64-bit words of data
	// 2 TDC events are stored in each 64-bit chunk of packet data
	uint32_t tdcEventCount = pkt->length * 2;


	// event encoding:
	// Bits 31 downto 8: event timestamp in TDC bins relative to packet
	// 		             timestamp
	// Bits 7 downto 4: event flags
	// Bits 3 downto 0: channel number
	uint32_t* tdcEventData = (uint32_t*)(pkt->data);

	// each TDC packet covers up to 3 coarse TDC periods
	// the end of one period is marked by an event on channel 15
	uint32_t rolloverEra = 0;
	// print all TDC timestamps of the packet
	for (uint32_t i = 0; i < tdcEventCount; i++) {
		// TDC channel number
		// 0 - 3: LEMO inputs
		// 15: internal marker: end of current TDC time frame
		uint32_t tdcChannel = tdcEventData[i] & 0xf;
		// event flags
		uint32_t flags = (tdcEventData[i] >> 4) & 0xf;
		// 24-bit timestamp
		uint32_t event_ts = tdcEventData[i] >> 8;

		// valid input channel?
		if (tdcChannel < 4) {
			// add accumulated rollovers since start of packet
			event_ts += rolloverEra;
			// calculate timestamp of TDC event in picoseconds
			double edgeTsPs = event_ts * pi->tdc_period;
			edgeTsPs += packetTs;
			ProcessTDCTimestamp(tdcChannel, edgeTsPs);
			printf("TDC event on channel %d timestamp: packet without "
				"shift %.3f ns, "
				"with shift %.3f ns, edge %.3f ns  \n",
				tdcChannel, (double)(pkt->timestamp * pi->packet_ts_period) / 1000.0,
				packetTs / 1000., edgeTsPs / 1000.);

		}

		if (tdcChannel == 14) {
			// dummy data, can be ignored
		}

		// rollover marker
		if (tdcChannel == 15) {
			rolloverEra += pi->tdc_rollover_period;
		}
	}
}

void Ndigo6GApp::ConfigureTDC(ndigo6g12_configuration* config) {
	// enable TDC channels
	for (int i = 0; i < NDIGO6G12_TDC_CHANNEL_COUNT; i++) {
		// for NIM pulses: trigger at -350 mV
		config->tdc_trigger_offsets[i] = NDIGO6G12_DC_OFFSET_N_NIM;

		// enable TDC channel
		config->tdc_configuration.channel[i].enable = (tdcChannelMask & (1 << i)) != 0;

		// enable falling edge trigger as input to trigger matrix for selected
		// TDC channel 
		// only required if used as trigger source for Gating, TiGer
		// or ADC trigger blocks
		config->trigger[NDIGO6G12_TRIGGER_TDC0 + i].edge = true;
		config->trigger[NDIGO6G12_TRIGGER_TDC0 + i].rising = false;
		// threshold not applicable for TDC inputs
		// trigger threshold is set via tdc_trigger_offsets[i]
		config->trigger[NDIGO6G12_TRIGGER_TDC0 + i].threshold = 0;
	}
}