[libsigrok.git] / src / hardware / raspberrypi-pico / protocol.c

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2022 Shawn Walker <ac0bi00@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#define _GNU_SOURCE

#include <config.h>
#include <errno.h>
#include <glib.h>
#include <math.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"
#include "protocol.h"

SR_PRIV int send_serial_str(struct sr_serial_dev_inst *serial, char *str)
{
	int len = strlen(str);
	if ((len > 15) || (len < 1)) {	//limit length to catch errant strings
		sr_err("ERROR:Serial string len %d invalid ", len);
		return SR_ERR;
	}
	//100ms timeout. With USB CDC serial we can't define the timeout
	//based on link rate, so just pick something large as we shouldn't normally see them
	if (serial_write_blocking(serial, str, len, 100) != len) {
		sr_err("ERROR:Serial str write failed");
		return SR_ERR;
	}

	return SR_OK;
}

SR_PRIV int send_serial_char(struct sr_serial_dev_inst *serial, char ch)
{
	char buf[1];
	buf[0] = ch;
	if (serial_write_blocking(serial, buf, 1, 100) != 1) {	//100ms
		sr_err("ERROR:Serial char write failed");
		return SR_ERR;
	}
	return SR_OK;
}

//Issue a command that expects a string return, return length of string
int send_serial_w_resp(struct sr_serial_dev_inst *serial, char *str,
		       char *resp, size_t cnt)
{
	int num_read, i;
	send_serial_str(serial, str);
	//Using the serial_read_blocking function when reading a response of unknown length requires 
	//a long worst case timeout to always be taken.  So, instead loop waiting for a first byte, and
	//then a final small delay for the rest. 
	for (i = 0; i < 1000; i++) {	//wait up to 1 second in ms increments
		num_read = serial_read_blocking(serial, resp, cnt, 1);
		if (num_read > 0)
			break;
	}
	//sr_spew("rwprsp1 i %d nr %d",i,num_read);
	//Since the serial port is usb CDC we can't calculate timeouts based on baud rate but
	//even if the response is split between two USB transfers 10ms should be plenty.
	num_read +=
	    serial_read_blocking(serial, &(resp[num_read]), cnt - num_read,
				 10);
	//sr_spew("rwrsp2 nr %d",num_read);

	if ((num_read < 1) || (num_read > 30)) {
		sr_err("ERROR:Serial_w_resp failed (%d).", num_read);
		return -1;
	} else {
		return num_read;
	}
}

//Issue a command that expects a single char ack 
SR_PRIV int send_serial_w_ack(struct sr_serial_dev_inst *serial, char *str)
{
	char buf[2];
	int num_read;
	//In case we have left over transfer from the device, drain them
	while ((num_read = serial_read_blocking(serial, buf, 2, 10))) {
		//sr_dbg("swack drops 2 previous bytes %d %d",buf[0],buf[1]);
	}
	send_serial_str(serial, str);
	//1000ms timeout
	num_read = serial_read_blocking(serial, buf, 1, 1000);
	if ((num_read == 1) && (buf[0] == '*')) {
		return SR_OK;
	} else {
		sr_err("ERROR:Serial_w_ack %s failed (%d).", str,
		       num_read);
		if (num_read) {
			sr_err("ack resp char %c d %d\n\r", buf[0],
			       buf[0]);
		}
		return SR_ERR;
	}
}

//Process incoming data stream assuming it is optimized packing of 4 channels or less
//Each byte is 4 channels of data and a 3 bit rle value, or a larger rle value, or a control signal.
//This also checks for aborts and ends.
//If an end is seen we stop processing but do not check the byte_cnt
//The output is a set of samples fed to process group to perform sw triggering and sending of data to the session
//as well as maintenance of the serial rx byte cnt.
//Since we can get huge rle values we chop them up for processing into smaller groups
//In this mode we can always consume all bytes because there are no cases where the processing of one 
//byte requires the one after it.
void process_D4(struct sr_dev_inst *sdi, struct dev_context *d)
{
	uint32_t j;
	uint8_t cbyte;
	uint8_t cval;
	uint32_t rlecnt = 0;
	while (d->ser_rdptr < d->bytes_avail) {
		cbyte = d->buffer[(d->ser_rdptr)];
		//RLE only byte
		if (cbyte >= 48 && cbyte <= 127) {
			rlecnt += (cbyte - 47) * 8;
			d->byte_cnt++;
		} else if (cbyte >= 0x80) {	//sample with possible rle
			rlecnt += (cbyte & 0x70) >> 4;
			if (rlecnt) {
				//On a value change, duplicate the previous values first.
				rle_memset(d, rlecnt);
				rlecnt = 0;
			}
			//Finally add in the new values
			cval = cbyte & 0xF;
                        uint32_t didx=(d->cbuf_wrptr) * (d->dig_sample_bytes);
			d->d_data_buf[didx] = cval;
			//pad in all other bytes since the sessions even wants disabled channels reported
			for (j = 1; j < d->dig_sample_bytes; j++) {
				d->d_data_buf[didx+j] = 0;
			}
			d->byte_cnt++;
			sr_spew
			    ("Dchan4 rdptr %d wrptr %d bytein 0x%X rle %d cval 0x%X didx %d\n",
			     (d->ser_rdptr) - 1, d->cbuf_wrptr, cbyte,
			     rlecnt, cval,didx);
                        d->cbuf_wrptr++;
			rlecnt = 0;
			d->d_last[0] = cval;
		}
		//Any other character ends parsing - it could be a frame error or a start of the final byte cnt
		else {
			if (cbyte == '$') {
				sr_info
				    ("D4 Data stream stops with cbyte %d char %c rdidx %d cnt %llu",
				     cbyte, cbyte, d->ser_rdptr,
				     d->byte_cnt);
				d->rxstate = RX_STOPPED;
			} else {
				sr_err
				    ("D4 Data stream aborts with cbyte %d char %c rdidx %d cnt %llu",
				     cbyte, cbyte, d->ser_rdptr,
				     d->byte_cnt);
				d->rxstate = RX_ABORT;
			}
			break;	//break from while loop
		}
		(d->ser_rdptr)++;
		//To ensure we don't overflow the sample buffer, but still send it large chunks of data 
		//(to make the packet sends to the session efficient) only call process group after
		//a large number of samples have been seen.
                //cbuf_wrptr counts slices, so shift right by 2 to create a worst case x4 multiple ratio of
                //cbuf_wrptr value to the depth of the sample buffer.
		//Likely we could use the max rle value of 640 but 1024 gives some extra room.
                //Also do a simple check of rlecnt>2000 since that is a reasonable minimal value to send to the session
		if ((rlecnt>=2000)
                     ||((rlecnt + ((d->cbuf_wrptr)<<2))) > (d->sample_buf_size - 1024)) {
                         sr_spew("D4 preoverflow wrptr %d bufsize %d rlecnt %d\n\r",d->cbuf_wrptr,d->sample_buf_size,rlecnt);
 			 rle_memset(d, rlecnt);
 			 process_group(sdi, d, d->cbuf_wrptr);
                         rlecnt=0;
		     }

	}//while rdptr < wrptr
	sr_spew("D4 while done rdptr %d", d->ser_rdptr);
	//If we reach the end of the serial input stream send any remaining values or rles to the session
	if (rlecnt) {
		sr_spew("Residual D4 slice rlecnt %d", rlecnt);
		rle_memset(d, rlecnt);
	}
	if (d->cbuf_wrptr) {
		sr_spew("Residual D4 data wrptr %d", d->cbuf_wrptr);
		process_group(sdi, d, d->cbuf_wrptr);

	}

} //Process_D4

//Process incoming data stream and forward to trigger processing with process_group
//The final value of ser_rdptr indicates how many bytes were processed.
//This version handles all other enabled channel configurations that Process_D4 doesn't
void process_slice(struct sr_dev_inst *sdi, struct dev_context *devc)
{
	int32_t i;
	uint32_t tmp32;
	uint8_t cbyte;
	uint32_t cword;
	uint32_t slice_bytes;	//number of bytes that have legal slice values including RLE
	//Only process legal data values for this mode which are 0x32-0x7F for RLE and 0x80 to 0xFF for data
	for (slice_bytes = 1; (slice_bytes < devc->bytes_avail)
	     && (devc->buffer[slice_bytes - 1] >= 0x30); slice_bytes++);
	if (slice_bytes != devc->bytes_avail) {
		cbyte = devc->buffer[slice_bytes - 1];
		slice_bytes--;	//Don't process the ending character
		if (cbyte == '$') {
			sr_info
			    ("Data stream stops with cbyte %d char %c rdidx %d sbytes %d cnt %llu",
			     cbyte, cbyte, devc->ser_rdptr, slice_bytes,
			     devc->byte_cnt);
			devc->rxstate = RX_STOPPED;
		} else {
			sr_err
			    ("Data stream aborts with cbyte %d char %c rdidx %d sbytes %d cnt %llu",
			     cbyte, cbyte, devc->ser_rdptr, slice_bytes,
			     devc->byte_cnt);
			devc->rxstate = RX_ABORT;
		}
	}
	//If the wrptr is non-zero due to a residual from the previous serial transfer don't double count it towards byte_cnt
	devc->byte_cnt += slice_bytes - (devc->wrptr);
	sr_spew("process slice avail %d rdptr %d sb %d byte_cnt %lld",
		devc->bytes_avail, devc->ser_rdptr, slice_bytes,
		devc->byte_cnt);
	//Must have a full slice or one rle byte
        while (((devc->ser_rdptr + devc->bytes_per_slice) <= slice_bytes) 
               ||((devc->ser_rdptr  < slice_bytes)&&(devc->buffer[devc->ser_rdptr] < 0x80))) { 

          if(devc->buffer[devc->ser_rdptr] < 0x80){
	     int16_t rlecnt;
	     if(devc->buffer[devc->ser_rdptr]<=79){
                rlecnt=devc->buffer[devc->ser_rdptr]-47;
             }else{ 
	       rlecnt=(devc->buffer[devc->ser_rdptr]-78)*32;
	     }
             sr_info("RLEcnt of %d in %d",rlecnt,devc->buffer[devc->ser_rdptr]);
             if((rlecnt < 1)||(rlecnt>1568)){
                sr_err("Bad rlecnt val %d in %d",rlecnt,devc->buffer[devc->ser_rdptr]);
             }else{
                rle_memset(devc,rlecnt);
             }
             devc->ser_rdptr++;

          }else{
		cword = 0;
		//build up a word 7 bits at a time, using only enabled channels
		for (i = 0; i < devc->num_d_channels; i += 7) {
			if (((devc->d_chan_mask) >> i) & 0x7F) {
				cword |=
				    ((devc->buffer[devc->ser_rdptr]) &
				     0x7F) << i;
				(devc->ser_rdptr)++;
			}
		}
		//and then distribute 8 bits at a time to all possible channels
                //but first save of cword for rle
                devc->d_last[0]=cword&0xFF;
                devc->d_last[1]=(cword>>8)&0xFF;
                devc->d_last[2]=(cword>>16)&0xFF;
                devc->d_last[3]=(cword>>24)&0xFF;
		for (i = 0; i < devc->num_d_channels; i += 8) {
			uint32_t idx =
			    ((devc->cbuf_wrptr) * devc->dig_sample_bytes) +
			    (i >> 3);
			devc->d_data_buf[idx] = cword & 0xFF;
			sr_spew
			    ("Dchan i %d wrptr %d idx %d char 0x%X cword 0x%X",
			     i, devc->cbuf_wrptr, idx,
			     devc->d_data_buf[idx], cword);
			cword >>= 8;
		}

		//Each analog value is a 7 bit value
		for (i = 0; i < devc->num_a_channels; i++) {
			if ((devc->a_chan_mask >> i) & 1) {
				//a_size is depracted and must always be 1B
				tmp32 =
				    devc->buffer[devc->ser_rdptr] - 0x80;
				devc->a_data_bufs[i][devc->cbuf_wrptr] =
				    ((float) tmp32 * devc->a_scale[i]) +
				    devc->a_offset[i];
				devc->a_last[i] =
				    devc->a_data_bufs[i][devc->cbuf_wrptr];
				sr_spew
				    ("AChan %d t32 %d value %f wrptr %d rdptr %d sc %f off %f",
				     i, tmp32,
				     devc->
				     a_data_bufs[i][devc->cbuf_wrptr],
				     devc->cbuf_wrptr, devc->ser_rdptr,
				     devc->a_scale[i], devc->a_offset[i]);
				devc->ser_rdptr++;
			}	//if channel enabled
		}		//for num_a_channels
		devc->cbuf_wrptr++;
           }//Not an RLE
           //RLEs can create a large number of samples relative to the incoming serial buffer
           //To prevent overflow of the sample data buffer we call process_group.
           //cbuf_wrptr and sample_buf_size are both in terms of slices
           //2048 is more than needed for a max rle of 1640 on the next incoming character
           if((devc->cbuf_wrptr +2048) >  devc->sample_buf_size){
              sr_spew("Drain large buff %d %d\n\r",devc->cbuf_wrptr,devc->sample_buf_size);
              process_group(sdi, devc, devc->cbuf_wrptr);

           }
	}//While another slice or RLE available
	if (devc->cbuf_wrptr){
		process_group(sdi, devc, devc->cbuf_wrptr);
	}

}

//Send the processed analog values to the session
int send_analog(struct sr_dev_inst *sdi, struct dev_context *devc,
		uint32_t num_samples, uint32_t offset)
{
	struct sr_datafeed_packet packet;
	struct sr_datafeed_analog analog;
	struct sr_analog_encoding encoding;
	struct sr_analog_meaning meaning;
	struct sr_analog_spec spec;
	struct sr_channel *ch;
	uint32_t i;
	float *fptr;

	sr_analog_init(&analog, &encoding, &meaning, &spec, ANALOG_DIGITS);
	for (i = 0; i < devc->num_a_channels; i++) {
		if ((devc->a_chan_mask >> i) & 1) {
			ch = devc->analog_groups[i]->channels->data;
			analog.meaning->channels =
			    g_slist_append(NULL, ch);
			analog.num_samples = num_samples;
			analog.data = (devc->a_data_bufs[i]) + offset;
			fptr = analog.data;
			sr_spew
			    ("send analog num %d offset %d first %f 2 %f",
			     num_samples, offset, *(devc->a_data_bufs[i]),
			     *fptr);
			analog.meaning->mq = SR_MQ_VOLTAGE;
			analog.meaning->unit = SR_UNIT_VOLT;
			analog.meaning->mqflags = 0;
			packet.type = SR_DF_ANALOG;
			packet.payload = &analog;
			sr_session_send(sdi, &packet);
			g_slist_free(analog.meaning->channels);
		}		//if enabled
	}			//for channels
	return 0;

}

//Send the ring buffer of pre-trigger analog samples.
//  The entire buffer is sent (as long as it filled once), but need send two payloads split at the 
//  the writeptr 
int send_analog_ring(struct sr_dev_inst *sdi, struct dev_context *devc,
		     uint32_t num_samples)
{
	struct sr_datafeed_packet packet;
	struct sr_datafeed_analog analog;
	struct sr_analog_encoding encoding;
	struct sr_analog_meaning meaning;
	struct sr_analog_spec spec;
	struct sr_channel *ch;
	int i;
	uint32_t num_pre, start_pre;
	uint32_t num_post, start_post;
	num_pre =
	    (num_samples >=
	     devc->pretrig_wr_ptr) ? devc->pretrig_wr_ptr : num_samples;
	start_pre = devc->pretrig_wr_ptr - num_pre;
	num_post = num_samples - num_pre;
	start_post = devc->pretrig_entries - num_post;
	sr_spew
	    ("send_analog ring wrptr %u ns %d npre %u spre %u npost %u spost %u",
	     devc->pretrig_wr_ptr, num_samples, num_pre, start_pre,
	     num_post, start_post);
	float *fptr;
	sr_analog_init(&analog, &encoding, &meaning, &spec, ANALOG_DIGITS);
	for (i = 0; i < devc->num_a_channels; i++) {
		if ((devc->a_chan_mask >> i) & 1) {
			ch = devc->analog_groups[i]->channels->data;
			analog.meaning->channels =
			    g_slist_append(NULL, ch);
			analog.meaning->mq = SR_MQ_VOLTAGE;
			analog.meaning->unit = SR_UNIT_VOLT;
			analog.meaning->mqflags = 0;
			packet.type = SR_DF_ANALOG;
			packet.payload = &analog;
			//First send what is after the write pointer because it is oldest
			if (num_post) {
				analog.num_samples = num_post;
				analog.data =
				    (devc->a_pretrig_bufs[i]) + start_post;
				//sr_spew("ring buf %d starts at %p",i,(void *) devc->a_pretrig_bufs[i]);
				//sr_spew("analog data %d starts at %p",i,(void *) analog.data);
				//sr_spew("Sending A%d ring buffer oldest ",i);
				for (uint32_t j = 0;
				     j < analog.num_samples; j++) {
					fptr =
					    analog.data +
					    (j * sizeof(float));
					//sr_spew("RNGDCT%d j %d %f %p",i,j,*fptr,(void *)fptr);
				}
				sr_session_send(sdi, &packet);
			}
			if (num_pre) {
				analog.num_samples = num_pre;
				analog.data =
				    (devc->a_pretrig_bufs[i]) + start_pre;
				sr_dbg("Sending A%d ring buffer newest ",
				       i);
				for (uint32_t j = 0;
				     j < analog.num_samples; j++) {
					fptr =
					    analog.data +
					    (j * sizeof(float));
					sr_spew("RNGDCW%d j %d %f %p", i,
						j, *fptr, (void *) fptr);
				}
				sr_session_send(sdi, &packet);
			}
			g_slist_free(analog.meaning->channels);
			sr_dbg("Sending A%d ring buffer done ", i);
		}		//if enabled
	}			//for channels
	return 0;

}

//Given a chunk of slices forward to trigger check or session as appropriate and update state
//these could be real slices or those generated by rles
int process_group(struct sr_dev_inst *sdi, struct dev_context *devc,
		  uint32_t num_slices)
{
	int trigger_offset;
	int pre_trigger_samples;
	//These are samples sent to session and are less than num_slices if we reach limit_samples
	size_t num_samples;
	struct sr_datafeed_logic logic;
	struct sr_datafeed_packet packet;
	int i;
	size_t cbuf_wrptr_cpy;
	cbuf_wrptr_cpy = devc->cbuf_wrptr;
	//regardless of whether we forward samples on or not (because we aren't triggered), always reset the 
	//pointer into the device data buffers 
	devc->cbuf_wrptr = 0;
	if (devc->trigger_fired) {	//send directly to session
		if (devc->limit_samples &&
		    num_slices >
		    devc->limit_samples - devc->sent_samples) {
			num_samples =
			    devc->limit_samples - devc->sent_samples;
		} else {
			num_samples = num_slices;
		}
		if (num_samples > 0) {
			sr_spew
			    ("Process_group sending %d post trig samples dsb %d",
			     num_samples, devc->dig_sample_bytes);
			//for(int z=0;(z<num_samples);z++){
			  // sr_spew("0x%X ",devc->d_data_buf[z]);
			//}
			if (devc->num_d_channels) {
				packet.type = SR_DF_LOGIC;
				packet.payload = &logic;
				//Size the number of bytes required to fit all of the channels
				logic.unitsize = devc->dig_sample_bytes;
				//The total length of the array sent
				logic.length =
				    num_samples * logic.unitsize;
				logic.data = devc->d_data_buf;
				sr_session_send(sdi, &packet);
			}
			send_analog(sdi, devc, num_samples, 0);
		}		//num_sample>0
		devc->sent_samples += num_samples;
		return 0;
	}			//trigger_fired
	else {
		size_t num_ring_samples;
		size_t sptr;
		size_t eptr;
		size_t numtail;
		size_t numwrap;
		size_t srcptr;
		//sr_spew("Process_group check %d pre trig samples",num_slices);
		//The trigger_offset is -1 if no trigger is found, but if a trigger is found
		//then trigger_offset is the offset into the data buffer sent to it.
		//The pre_trigger_samples is the total number of samples before the trigger, but limited to
		//the size of the ring buffer set by the capture_ratio. So the pre_trigger_samples can include both the new samples
		//and the ring buffer, but trigger_offset is only in relation to the new samples
		trigger_offset = soft_trigger_logic_check(devc->stl,
							  devc->d_data_buf,
							  num_slices *
							  devc->dig_sample_bytes,
							  &pre_trigger_samples);
		//A trigger offset >=0 indicate a trigger was seen.  The stl will isue the trigger to the session
		//and will forward all pre trigger logic samples, but we must send any post trigger logic 
		//and all pre and post trigger analog signals
		// sr_dbg("trggr_off %d",trigger_offset);
		// sr_dbg("pre_samp  %d",pre_trigger_samples);
		if (trigger_offset > -1) {
			devc->trigger_fired = TRUE;
			devc->sent_samples += pre_trigger_samples;
			packet.type = SR_DF_LOGIC;
			packet.payload = &logic;
			num_samples = num_slices - trigger_offset;
//Since we are in continuous mode for SW triggers it is possible to get more samples than limit_samples, so
//once the trigger fires make sure we don't get beyond limit samples. At this point sent_samples should
//be equal to pre_trigger_samples (just added above) because without being triggered we'd never increment
//sent_samples.
//This number is the number of post trigger logic samples to send to the session, the number of floats
//is larger because of the analog ring buffer we track.
			if (devc->limit_samples &&
			    num_samples >
			    devc->limit_samples - devc->sent_samples)
				num_samples =
				    devc->limit_samples -
				    devc->sent_samples;
			//The soft trigger logic issues the trigger and sends packest for all logic data that was pretrigger
			//so only send what is left
			if (num_samples > 0) {
				sr_dbg
				    ("Sending post trigger logical remainder of %d",
				     num_samples);
				logic.length =
				    num_samples * devc->dig_sample_bytes;
				logic.unitsize = devc->dig_sample_bytes;
				logic.data =
				    devc->d_data_buf +
				    (trigger_offset *
				     devc->dig_sample_bytes);
				devc->sent_samples += num_samples;
				sr_session_send(sdi, &packet);
			}
			size_t new_start, new_end, new_samples,
			    ring_samples;
			//Figure out the analog data to send.
			//We might need to send:
			//-some or all of incoming data
			//-all of incoming data and some of ring buffer
			//-all of incoming data and all of ring buffer (and still might be short)
			//We don't need to compare to limit_samples because pretrig_entries can never be more than limit_samples
			//trigger offset indicatese where in the new samples the trigger was, but we need to go back pretrig_entries before it             
			new_start =
			    (trigger_offset >
			     (int) devc->pretrig_entries) ? trigger_offset
			    - devc->pretrig_entries : 0;
			//Note that we might not have gotten all the pre triggerstore data we were looking for. In such a case the sw trigger
			//logic seems to fill up to the limit_samples and thus the ratio is off, but we get the full number of samples
			//The number of entries in the ring buffer is pre_trigger_samples-trigger_offset so subtract that from limit samples
			//as a threshold
			new_end =
			    MIN(num_slices - 1,
				devc->limit_samples -
				(pre_trigger_samples - trigger_offset) -
				1);
			//This includes pre and post trigger storage.
			new_samples = new_end - new_start + 1;
			//pre_trigger_samples can never be greater than trigger_offset by more than the ring buffer depth (pretrig entries) 
			ring_samples =
			    (pre_trigger_samples >
			     trigger_offset) ? pre_trigger_samples -
			    trigger_offset : 0;
			sr_spew
			    ("SW trigger float info newstart %zu new_end %zu new_samp %zu ring_samp %zu",
			     new_start, new_end, new_samples,
			     ring_samples);
			if (ring_samples > 0) {
				send_analog_ring(sdi, devc, ring_samples);
			}
			if (new_samples) {
				send_analog(sdi, devc, new_samples,
					    new_start);
			}

		}		//if trigger_offset 
		else {		//We didn't trigger but need to copy to ring buffer
			if ((devc->a_chan_mask) && (devc->pretrig_entries)) {
				//The incoming data buffer could be much larger than the ring buffer, so never copy more than 
				//the size of the ring buffer
				num_ring_samples =
				    num_slices >
				    devc->
				    pretrig_entries ? devc->pretrig_entries
				    : num_slices;
				sptr = devc->pretrig_wr_ptr;	//starting pointer to copy to
				//endptr can't go past the end
				eptr =
				    (sptr + num_ring_samples) >=
				    devc->
				    pretrig_entries ? devc->pretrig_entries
				    - 1 : sptr + num_ring_samples - 1;
				numtail = (eptr - sptr) + 1;	//number of samples to copy to the tail of ring buffer without wrapping
				numwrap =
				    (num_ring_samples >
				     numtail) ? num_ring_samples -
				    numtail : 0;
				//cbuf_wrptr points to where the next write should go, not  theactual write data
				srcptr = cbuf_wrptr_cpy - num_ring_samples;
				sr_spew("RNG num %zu sptr %zu eptr %zu ",
					num_ring_samples, sptr, eptr);
				//sr_spew("RNG srcptr %zu nt %zu nw %zu",srcptr,numtail,numwrap);
				for (i = 0; i < devc->num_a_channels; i++) {
					if ((devc->a_chan_mask >> i) & 1) {
						//copy tail
						for (uint32_t j = 0;
						     j < numtail; j++) {
							devc->a_pretrig_bufs
							    [i][sptr + j] =
							    devc->a_data_bufs
							    [i]
							    [srcptr + j];
							//sr_spew("RNGCpyT C%d src %zu dest %zu",i,srcptr+j,sptr+j);
						}	//for j
					}	//if chan_mask
				}	//for channels
				//Copy wrap
				srcptr += numtail;
				for (i = 0; i < devc->num_a_channels; i++) {
					if ((devc->a_chan_mask >> i) & 1) {
						for (uint32_t j = 0;
						     j < numwrap; j++) {
							devc->a_pretrig_bufs
							    [i][j] =
							    devc->a_data_bufs
							    [i]
							    [srcptr + j];
							//sr_spew("RNGCpyW C%d src %zu dest %zu",i,srcptr+j,j);
						}	//for j
					}	//if chan_mask
				}	//for channels
				devc->pretrig_wr_ptr =
				    (numwrap) ? numwrap : (eptr +
							   1) %
				    devc->pretrig_entries;
				//sr_dbg("RNG pwrptr new %u",devc->pretrig_wr_ptr);
			}	//if any analog channel enabled and pretrig_entries
		}		//else (trigger not detected)
	}			//trigger not set on function entry
	return 0;
}				//process_group


//Duplicate previous sample values
//This function relies on the caller to ensure d_data_buf has samples to handle the full value of the rle
void rle_memset(struct dev_context *devc, uint32_t num_slices)
{
	uint32_t j, k,didx;
	sr_spew("rle_memset vals 0x%X, 0x%X, 0x%X slices %d dsb %d\n", devc->d_last[0],devc->d_last[1],devc->d_last[2],
		num_slices, devc->dig_sample_bytes);
	//Even if a channel is disabled, PV expects the same location and size for the enabled
	// channels as if the channel were enabled.
	for (j = 0; j < num_slices; j++) {
                didx=devc->cbuf_wrptr*devc->dig_sample_bytes;
		for (k = 0; k < devc->dig_sample_bytes; k++) {
			devc->d_data_buf[didx + k] =  devc->d_last[k];
			//	sr_spew("k %d j %d v 0x%X p %d didx %d",k,j,devc->d_data_buf[(devc->cbuf_wrptr)+k],(devc->cbuf_wrptr)+k,didx);
		}
		// cbuf_wrptr always counts slices/samples (and not the bytes in the buffer)
                // regardless of mode
                devc->cbuf_wrptr++;
	}
        
}

//This callback function is mapped from api.c with serial_source_add and is created after a capture
//has been setup and is responsible for querying the device trigger status, downloading data
//and forwarding packets
SR_PRIV int raspberrypi_pico_receive(int fd, int revents, void *cb_data)
{
	struct sr_dev_inst *sdi;
	struct dev_context *devc;
	struct sr_serial_dev_inst *serial;
	uint32_t i;
	int len;
	uint32_t bytes_rem;
	uint32_t residual_bytes;
	(void) fd;

	if (!(sdi = cb_data))
		return TRUE;

	if (!(devc = sdi->priv))
		return TRUE;
	if (devc->rxstate != RX_ACTIVE) {
		//This condition is normal operation and expected to happen 
		//but printed as information
		sr_dbg("Reached non active state in receive %d",
		       devc->rxstate);
		//don't return - we may be waiting for a final bytecnt
		//return TRUE;
	}
	if (devc->rxstate == RX_IDLE) {
		//This is the normal end condition where we do one more receive
		//to make sure we get the full byte_cnt
		sr_dbg("Reached idle state in receive %d", devc->rxstate);
		return FALSE;
	}

	serial = sdi->conn;
	//return true if it is some kind of event we don't handle
	if (!(revents == G_IO_IN || revents == 0))
		return TRUE;
	//Fill the buffer, note the end may have partial slices
	bytes_rem = devc->serial_buffer_size - devc->wrptr;
	//Read one byte less so that we can null it and print as a string
	//Do a small 10ms timeout, if we get nothing, we'll always come back again
	len =
	    serial_read_blocking(serial, &(devc->buffer[devc->wrptr]),
				 bytes_rem - 1, 10);
	sr_spew("Entry wrptr %u bytes_rem %u len %d", devc->wrptr,
		bytes_rem, len);

	if (len > 0) {
		devc->buffer[devc->wrptr + len] = 0;
		//Add the "#" so that spaces are clearly seen
		sr_dbg("rx string %s#", devc->buffer);
		//This is not guaranteed to be a dataloss condition, but definitely indicates we are 
		//processing data right at the incoming rate.
		//With the addition of the byte_cnt sent at the end we will detect any dataloss conditions
		//and thus this is disabled
		//if(len>=(int)bytes_rem-8){
		//  sr_err("ERROR: Serial buffer near or at max depth, data from device may have been lost");
		//}
		devc->bytes_avail = (devc->wrptr + len);
		sr_spew
		    ("rx len %d bytes_avail %ul sent_samples %ul wrptr %u",
		     len, devc->bytes_avail, devc->sent_samples,
		     devc->wrptr);
		//sr_err("rx len %d ",len);
	} else if (len == 0) {
		return TRUE;
	} else {
		sr_err("ERROR:Negative serial read code %d", len);
		sdi->driver->dev_acquisition_stop(sdi);
		return FALSE;
	}			//len>0
	//This can be used as a bit bucket to drop all samples to see how host processing time effects
	//the devices ability to send data. Obviously no data will be forwarded to the session so it will hang
	//        return TRUE; 

	//Process the serial read data
	devc->ser_rdptr = 0;
	if (devc->rxstate == RX_ACTIVE) {
		if ((devc->a_chan_mask == 0)
		    && ((devc->d_chan_mask & 0xFFFFFFF0) == 0)) {
			process_D4(sdi, devc);
		} else {
			process_slice(sdi, devc);
		}
	}
	//process_slice/process_D4 increment ser_rdptr as bytes of the serial buffer are used
	//But they may not use all of it, and thus the residual unused bytes are shifted to the start of the buffer
	//for the next call.
	residual_bytes = devc->bytes_avail - devc->ser_rdptr;
	//sr_spew("Residuals resid %d avail %d rdptr %d wrptr %d\n",residual_bytes,devc->bytes_avail,devc->ser_rdptr,devc->wrptr);
	if (residual_bytes) {
		for (i = 0; i < residual_bytes; i++) {
			devc->buffer[i] =
			    devc->buffer[i + devc->ser_rdptr];
		}
		devc->ser_rdptr = 0;
		devc->wrptr = residual_bytes;
		sr_spew("Residual shift rdptr %u wrptr %u",
			devc->ser_rdptr, devc->wrptr);
	} else {
		//If there are no residuals shifted then zero the wrptr since all data is used
		devc->wrptr = 0;
	}
	//ABORT ends immediately
	if (devc->rxstate == RX_ABORT) {
		sr_err("Ending receive on abort");
		sdi->driver->dev_acquisition_stop(sdi);
		return FALSE;	//
	}
	//if stopped look for final '+' indicating the full byte_cnt is received
	if (devc->rxstate == RX_STOPPED) {
		sr_dbg("Stopped, checking byte_cnt");
		if (devc->buffer[0] != '$') {
			//If this happens it means that we got a set of data that was not processed as
			//whole groups of slice bytes. So either we lost data or are not parsing it correctly.
			sr_err("ERROR: Stop marker should be byte zero");
			devc->rxstate = RX_ABORT;
			sdi->driver->dev_acquisition_stop(sdi);
			return FALSE;
		}
		for (i = 1; i < devc->wrptr; i++) {
			if (devc->buffer[i] == '+') {
				devc->buffer[i] = 0;
				uint64_t rxbytecnt;
				rxbytecnt = atol((char *)&(devc->buffer[1]));
				sr_dbg
				    ("Byte_cnt check device cnt %llu host cnt %llu",
				     rxbytecnt, devc->byte_cnt);
				if (rxbytecnt != devc->byte_cnt) {
					sr_err
					    ("ERROR: received %llu and counted %llu bytecnts don't match, data may be lost",
					     rxbytecnt, devc->byte_cnt);
				}
				//Since we got the bytecnt we know the device is done sending data
				devc->rxstate = RX_IDLE;
				//We must always call acquisition_stop on all completed runs
				sdi->driver->dev_acquisition_stop(sdi);
				return TRUE;
			}
		}
		//It's possible we need one more serial transfer to get the byte_cnt, so print that here
		sr_dbg("Haven't seen byte_cnt + yet");
	}			//RX_STOPPED
	//If at the sample limit, send a "+" in case we are in continuous mode and need
	//to stop the device.  Not that even in non continous mode there might be cases where get an extra
	//sample or two...

	if ((devc->sent_samples >= devc->limit_samples)
	    && (devc->rxstate == RX_ACTIVE)) {
		sr_dbg
		    ("Ending: sent %u of limit %llu samples byte_cnt %llu",
		     devc->sent_samples, devc->limit_samples,
		     devc->byte_cnt);
		send_serial_char(serial, '+');

	}
	sr_spew
	    ("Receive function done: sent %u limit %llu wrptr %u len %d",
	     devc->sent_samples, devc->limit_samples, devc->wrptr, len);
	return TRUE;
}				//raspberrypi_pico_receive

//Read device specific information from the device
SR_PRIV int raspberrypi_pico_get_dev_cfg(const struct sr_dev_inst *sdi)
{
	struct dev_context *devc;
	struct sr_serial_dev_inst *serial;
	char *cmd, response[20];
	gchar **tokens;
	unsigned int i;
	int ret, num_tokens;

	devc = sdi->priv;
	sr_dbg("At get_dev_cfg");
	serial = sdi->conn;
	for (i = 0; i < devc->num_a_channels; i++) {
		cmd = g_strdup_printf("a%d\n", i);
		ret = send_serial_w_resp(serial, cmd, response, 20);
		if (ret <= 0) {
			sr_err
			    ("ERROR:No response from device for analog channel query");
			return SR_ERR;
		}
		//null end of string for strsplit
		response[ret] = 0;
		tokens = NULL;
		tokens = g_strsplit(response, "x", 0);
		num_tokens = g_strv_length(tokens);
		if (num_tokens == 2) {
			devc->a_scale[i] =
			    ((float) atoi(tokens[0])) / 1000000.0;
			devc->a_offset[i] =
			    ((float) atoi(tokens[1])) / 1000000.0;
			sr_dbg
			    ("A%d scale %f offset %f response #%s# tokens #%s# #%s#\n",
			     i, devc->a_scale[i], devc->a_offset[i],
			     response, tokens[0], tokens[1]);
		} else {
			sr_err
			    ("ERROR:Ascale read c%d got unparseable response %s tokens %d",
			     i, response, num_tokens);
			//force a legal fixed value assuming a 3.3V scale
			//a failue in parsing the scale
			devc->a_scale[i] = 0.0257;
			devc->a_offset[i] = 0.0;
		}
		g_strfreev(tokens);
		g_free(cmd);
	}


	return SR_OK;

}