RHReliableDatagram.cpp

// RHReliableDatagram.cpp
//
// Define addressed datagram
//
// Part of the Arduino RH library for operating with HopeRF RH compatible transceivers
// (see http://www.hoperf.com)
// RHDatagram will be received only by the addressed node or all nodes within range if the
// to address is RH_BROADCAST_ADDRESS
//
// Author: Mike McCauley (mikem@airspayce.com)
// Copyright (C) 2011 Mike McCauley
// Adapted for RF22B on Raspeberry PI by Istvan Z. Kovacs, 2019
// $Id: RHReliableDatagram.cpp,v 1.18 2018/11/08 02:31:43 mikem Exp $

#include <RHReliableDatagram.h>

////////////////////////////////////////////////////////////////////
// Constructors
RHReliableDatagram::RHReliableDatagram(RHGenericDriver& driver, uint8_t thisAddress)
    : RHDatagram(driver, thisAddress)
{
    _retransmissions = 0;
    _lastSequenceNumber = 0;
    _timeout = RH_DEFAULT_TIMEOUT;
    _retries = RH_DEFAULT_RETRIES;
    memset(_seenIds, 0, sizeof(_seenIds));
}

////////////////////////////////////////////////////////////////////
// Public methods
void RHReliableDatagram::setTimeout(uint16_t timeout)
{
    _timeout = timeout;
}

////////////////////////////////////////////////////////////////////
void RHReliableDatagram::setRetries(uint8_t retries)
{
    _retries = retries;
}

////////////////////////////////////////////////////////////////////
uint8_t RHReliableDatagram::retries()
{
    return _retries;
}

////////////////////////////////////////////////////////////////////
bool RHReliableDatagram::sendtoWait(uint8_t* buf, uint8_t len, uint8_t address)
{
    // Assemble the message
    uint8_t thisSequenceNumber = ++_lastSequenceNumber;
    uint8_t retries = 0;
    while (retries++ <= _retries)
    {
        setHeaderId(thisSequenceNumber);

        // Set and clear header flags depending on if this is an
        // initial send or a retry.
        uint8_t headerFlagsToSet = RH_FLAGS_NONE;
        // Always clear the ACK flag
        uint8_t headerFlagsToClear = RH_FLAGS_ACK;
        if (retries == 1) {
            // On an initial send, clear the RETRY flag in case
            // it was previously set
            headerFlagsToClear |= RH_FLAGS_RETRY;
        } else {
            // Not an initial send, set the RETRY flag
            headerFlagsToSet = RH_FLAGS_RETRY;
        }
        setHeaderFlags(headerFlagsToSet, headerFlagsToClear);

        sendto(buf, len, address);
#if (RH_PLATFORM == RH_PLATFORM_RASPI)
        // _driver.send(...) already uses waitPacketSent()
#else
        waitPacketSent();
#endif

        // Never wait for ACKS to broadcasts:
        if (address == RH_BROADCAST_ADDRESS)
            return true;

        if (retries > 1)
            _retransmissions++;
        unsigned long thisSendTime = millis(); // Timeout does not include original transmit time

        // Compute a new timeout, random between _timeout and _timeout*2
        // This is to prevent collisions on every retransmit
        // if 2 nodes try to transmit at the same time
    #if (RH_PLATFORM == RH_PLATFORM_RASPI) // use standard library random(), bugs in random(min, max)
        uint16_t timeout = _timeout + (_timeout * (random() & 0xFF) / 256);
    #else
        uint16_t timeout = _timeout + (_timeout * random(0, 256) / 256);
    #endif
        int32_t timeLeft;
        while ((timeLeft = timeout - (millis() - thisSendTime)) > 0)
        {
            if (waitAvailableTimeout(timeLeft))
            {
                uint8_t from, to, id, flags;
                if (recvfrom(0, 0, &from, &to, &id, &flags)) // Discards the message
                {
                    // Now have a message: is it our ACK?
                    if (   from == address
                       && to == _thisAddress
                       && (flags & RH_FLAGS_ACK)
                       && (id == thisSequenceNumber))
                    {
                    // Its the ACK we are waiting for
                    return true;
                    }
                    else if (   !(flags & RH_FLAGS_ACK)
                        && (id == _seenIds[from]))
                    {
                    // This is a request we have already received. ACK it again
                    acknowledge(id, from);
                    }
                    // Else discard it
                }
            }
            // Not the one we are waiting for, maybe keep waiting until timeout exhausted
            YIELD;
        }
        // Timeout exhausted, maybe retry
        YIELD;
    }
    // Retries exhausted
    return false;
}

////////////////////////////////////////////////////////////////////
bool RHReliableDatagram::recvfromAck(uint8_t* buf, uint8_t* len, uint8_t* from, uint8_t* to, uint8_t* id, uint8_t* flags)
{
    uint8_t _from;
    uint8_t _to;
    uint8_t _id;
    uint8_t _flags;
    // Get the message before its clobbered by the ACK (shared rx and tx buffer in some drivers
#if (RH_PLATFORM == RH_PLATFORM_RASPI)
    // Pooling of nIRQ is used instead of a real interrupt service/handler
    // I.e. available() has been already called and the RX fifo buffer was checked & read (see e.g. RH_RF22B)
    if (recvfrom(buf, len, &_from, &_to, &_id, &_flags))
#else
    if (available() && recvfrom(buf, len, &_from, &_to, &_id, &_flags))
#endif
    {
        // Never ACK an ACK
        if (!(_flags & RH_FLAGS_ACK))
        {
            // Its a normal message not an ACK
            if (_to ==_thisAddress)
            {
                // Its for this node and
                // Its not a broadcast, so ACK it
                // Acknowledge message with ACK set in flags and ID set to received ID
                acknowledge(_id, _from);
            }
            // Filter out retried messages that we have seen before. This explicitly
            // only filters out messages that are marked as retries to protect against
            // the scenario where a transmitting device sends just one message and
            // shuts down between transmissions. Devices that do this will report the
            // the same ID each time since their internal sequence number will reset
            // to zero each time the device starts up.
            if ((RH_ENABLE_EXPLICIT_RETRY_DEDUP && !(_flags & RH_FLAGS_RETRY)) || _id != _seenIds[_from])
            {
                if (from)  *from =  _from;
                if (to)    *to =    _to;
                if (id)    *id =    _id;
                if (flags) *flags = _flags;
                _seenIds[_from] = _id;
                return true;
            }
            // Else just re-ack it and wait for a new one
        }
    }
    // No message for us available
    return false;
}

bool RHReliableDatagram::recvfromAckTimeout(uint8_t* buf, uint8_t* len, uint16_t timeout, uint8_t* from, uint8_t* to, uint8_t* id, uint8_t* flags)
{
    unsigned long starttime = millis();
    int32_t timeLeft;
    while ((timeLeft = timeout - (millis() - starttime)) > 0)
    {
	if (waitAvailableTimeout(timeLeft))
	{
	    if (recvfromAck(buf, len, from, to, id, flags))
		return true;
	}
	YIELD;
    }
    return false;
}

uint32_t RHReliableDatagram::retransmissions()
{
    return _retransmissions;
}

void RHReliableDatagram::resetRetransmissions()
{
    _retransmissions = 0;
}

void RHReliableDatagram::acknowledge(uint8_t id, uint8_t from)
{
    setHeaderId(id);
    setHeaderFlags(RH_FLAGS_ACK);
    // We would prefer to send a zero length ACK,
    // but if an RH_RF22 receives a 0 length message with a CRC error, it will never receive
    // a 0 length message again, until its reset, which makes everything hang :-(
    // So we send an ACK of 1 octet
    // REVISIT: should we send the RSSI for the information of the sender?
    uint8_t ack = '!';
    sendto(&ack, sizeof(ack), from);
#if (RH_PLATFORM == RH_PLATFORM_RASPI)
    // _driver.send(...) already uses waitPacketSent()
#else
    waitPacketSent();
#endif
}