firmware/src/mesh/RadioLibInterface.cpp

#include "RadioLibInterface.h"
#include "MeshTypes.h"
#include "OSTimer.h"
#include "mesh-pb-constants.h"
#include <NodeDB.h> // FIXME, this class shouldn't need to look into nodedb
#include <configuration.h>
#include <pb_decode.h>
#include <pb_encode.h>

// FIXME, we default to 4MHz SPI, SPI mode 0, check if the datasheet says it can really do that
static SPISettings spiSettings(4000000, MSBFIRST, SPI_MODE0);

RadioLibInterface::RadioLibInterface(RADIOLIB_PIN_TYPE cs, RADIOLIB_PIN_TYPE irq, RADIOLIB_PIN_TYPE rst, RADIOLIB_PIN_TYPE busy,
                                     SPIClass &spi, PhysicalLayer *_iface)
    : module(cs, irq, rst, busy, spi, spiSettings), iface(_iface)
{
    assert(!instance); // We assume only one for now
    instance = this;
}

#ifndef NO_ESP32
// ESP32 doesn't use that flag
#define YIELD_FROM_ISR(x) portYIELD_FROM_ISR()
#else
#define YIELD_FROM_ISR(x) portYIELD_FROM_ISR(x)
#endif

void INTERRUPT_ATTR RadioLibInterface::isrLevel0Common(PendingISR cause)
{
    instance->disableInterrupt();

    instance->pending = cause;
    BaseType_t xHigherPriorityTaskWoken;
    instance->notifyFromISR(&xHigherPriorityTaskWoken, cause, eSetValueWithOverwrite);

    /* Force a context switch if xHigherPriorityTaskWoken is now set to pdTRUE.
    The macro used to do this is dependent on the port and may be called
    portEND_SWITCHING_ISR. */
    YIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

void INTERRUPT_ATTR RadioLibInterface::isrRxLevel0()
{
    isrLevel0Common(ISR_RX);
}

void INTERRUPT_ATTR RadioLibInterface::isrTxLevel0()
{
    isrLevel0Common(ISR_TX);
}

/** Our ISR code currently needs this to find our active instance
 */
RadioLibInterface *RadioLibInterface::instance;

/**
 * Convert our modemConfig enum into wf, sf, etc...
 */
void RadioLibInterface::applyModemConfig()
{
    RadioInterface::applyModemConfig();

    switch (modemConfig) {
    case Bw125Cr45Sf128: ///< Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on. Default medium range
        bw = 125;
        cr = 5;
        sf = 7;
        break;
    case Bw500Cr45Sf128: ///< Bw = 500 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on. Fast+short range
        bw = 500;
        cr = 5;
        sf = 7;
        break;
    case Bw31_25Cr48Sf512: ///< Bw = 31.25 kHz, Cr = 4/8, Sf = 512chips/symbol, CRC on. Slow+long range
        bw = 31.25;
        cr = 8;
        sf = 9;
        break;
    case Bw125Cr48Sf4096:
        bw = 125;
        cr = 8;
        sf = 12;
        break;
    default:
        assert(0); // Unknown enum
    }
}

/** Could we send right now (i.e. either not actively receving or transmitting)? */
bool RadioLibInterface::canSendImmediately()
{
    // We wait _if_ we are partially though receiving a packet (rather than just merely waiting for one).
    // To do otherwise would be doubly bad because not only would we drop the packet that was on the way in,
    // we almost certainly guarantee no one outside will like the packet we are sending.
    bool busyTx = sendingPacket != NULL;
    bool busyRx = isReceiving && isActivelyReceiving();

    if (busyTx || busyRx) {
        if (busyTx)
            DEBUG_MSG("Can not send yet, busyTx\n");
        if (busyRx)
            DEBUG_MSG("Can not send yet, busyRx\n");
        return false;
    } else
        return true;
}

/// Send a packet (possibly by enquing in a private fifo).  This routine will
/// later free() the packet to pool.  This routine is not allowed to stall because it is called from
/// bluetooth comms code.  If the txmit queue is empty it might return an error
ErrorCode RadioLibInterface::send(MeshPacket *p)
{
    DEBUG_MSG("enqueuing for send on mesh fr=0x%x,to=0x%x,id=%d (txGood=%d,rxGood=%d,rxBad=%d)\n", p->from, p->to, p->id, txGood,
              rxGood, rxBad);
    ErrorCode res = txQueue.enqueue(p, 0) ? ERRNO_OK : ERRNO_UNKNOWN;

    if (res != ERRNO_OK) { // we weren't able to queue it, so we must drop it to prevent leaks
        packetPool.release(p);
        return res;
    }

    // We want all sending/receiving to be done by our daemon thread, We use a delay here because this packet might have been sent
    // in response to a packet we just received.  So we want to make sure the other side has had a chance to reconfigure its radio
    startTransmitTimer(true);

    return res;
}

bool RadioLibInterface::canSleep()
{
    bool res = txQueue.isEmpty();
    if (!res) // only print debug messages if we are vetoing sleep
        DEBUG_MSG("radio wait to sleep, txEmpty=%d\n", txQueue.isEmpty());

    return res;
}

/** At the low end we want to pick a delay large enough that anyone who just completed sending (some other node)
 * has had enough time to switch their radio back into receive mode.
 */
#define MIN_TX_WAIT_MSEC 100

/**
 * At the high end, this value is used to spread node attempts across time so when they are replying to a packet
 * they don't both check that the airwaves are clear at the same moment.  As long as they are off by some amount
 * one of the two will be first to start transmitting and the other will see that.  I bet 500ms is more than enough
 * to guarantee this.
 */
#define MAX_TX_WAIT_MSEC 2000 // stress test would still fail occasionally with 1000

/** radio helper thread callback.

We never immediately transmit after any operation (either rx or tx).  Instead we should start receiving and
wait a random delay of 50 to 200 ms to make sure we are not stomping on someone else.  The 50ms delay at the beginning ensures all
possible listeners have had time to finish processing the previous packet and now have their radio in RX state.  The up to 200ms
random delay gives a chance for all possible senders to have high odds of detecting that someone else started transmitting first
and then they will wait until that packet finishes.

NOTE: the large flood rebroadcast delay might still be needed even with this approach.  Because we might not be able to hear other
transmitters that we are potentially stomping on.  Requires further thought.

FIXME, the MIN_TX_WAIT_MSEC and MAX_TX_WAIT_MSEC values should be tuned via logic analyzer later.
*/
void RadioLibInterface::loop()
{
    pending = ISR_NONE;

    switch (notification) {
    case ISR_TX:
        handleTransmitInterrupt();
        startReceive();
        startTransmitTimer();
        break;
    case ISR_RX:
        handleReceiveInterrupt();
        startReceive();
        startTransmitTimer();
        break;
    case TRANSMIT_DELAY_COMPLETED:
        // If we are not currently in receive mode, then restart the timer and try again later (this can happen if the main thread
        // has placed the unit into standby)  FIXME, how will this work if the chipset is in sleep mode?
        if (!txQueue.isEmpty()) {
            if (!canSendImmediately()) {
                startTransmitTimer(); // try again in a little while
            } else {
                // Send any outgoing packets we have ready
                MeshPacket *txp = txQueue.dequeuePtr(0);
                assert(txp);
                startSend(txp);
            }
        }
        break;
    default:
        assert(0); // We expected to receive a valid notification from the ISR
    }
}

#ifndef NO_ESP32
#define USE_HW_TIMER
#else
// Not needed on NRF52
#define IRAM_ATTR
#endif

void IRAM_ATTR RadioLibInterface::timerCallback(void *p1, uint32_t p2)
{
    RadioLibInterface *t = (RadioLibInterface *)p1;

    t->timerRunning = false;

    // We use without overwrite, so that if there is already an interrupt pending to be handled, that gets handle properly (the
    // ISR handler will restart our timer)
#ifndef USE_HW_TIMER
    t->notify(TRANSMIT_DELAY_COMPLETED, eSetValueWithoutOverwrite);
#else
    BaseType_t xHigherPriorityTaskWoken;
    instance->notifyFromISR(&xHigherPriorityTaskWoken, TRANSMIT_DELAY_COMPLETED, eSetValueWithoutOverwrite);

    /* Force a context switch if xHigherPriorityTaskWoken is now set to pdTRUE.
    The macro used to do this is dependent on the port and may be called
    portEND_SWITCHING_ISR. */
    YIELD_FROM_ISR(xHigherPriorityTaskWoken);
#endif
}

void RadioLibInterface::startTransmitTimer(bool withDelay)
{
    // If we have work to do and the timer wasn't already scheduled, schedule it now
    if (!timerRunning && !txQueue.isEmpty()) {
        timerRunning = true;
        uint32_t delay =
            !withDelay ? 0 : random(MIN_TX_WAIT_MSEC, MAX_TX_WAIT_MSEC); // See documentation for loop() wrt these values
                                                                         // DEBUG_MSG("xmit timer %d\n", delay);
#ifdef USE_HW_TIMER
        bool okay = scheduleHWCallback(timerCallback, this, 0, delay);
#else
        bool okay = scheduleOSCallback(timerCallback, this, 0, delay);
#endif
        assert(okay);
    }
}

void RadioLibInterface::handleTransmitInterrupt()
{
    // DEBUG_MSG("handling lora TX interrupt\n");
    assert(sendingPacket); // Were we sending? - FIXME, this was null coming out of light sleep due to RF95 ISR!

    completeSending();
}

void RadioLibInterface::completeSending()
{
    if (sendingPacket) {
        txGood++;
        DEBUG_MSG("Completed sending to=0x%x, id=%u\n", sendingPacket->to, sendingPacket->id);

        // We are done sending that packet, release it
        packetPool.release(sendingPacket);
        sendingPacket = NULL;
        // DEBUG_MSG("Done with send\n");
    }
}

void RadioLibInterface::handleReceiveInterrupt()
{
    assert(isReceiving);
    isReceiving = false;

    // read the number of actually received bytes
    size_t length = iface->getPacketLength();

    int state = iface->readData(radiobuf, length);
    if (state != ERR_NONE) {
        DEBUG_MSG("ignoring received packet due to error=%d\n", state);
        rxBad++;
    } else {
        // Skip the 4 headers that are at the beginning of the rxBuf
        int32_t payloadLen = length - sizeof(PacketHeader);
        const uint8_t *payload = radiobuf + sizeof(PacketHeader);

        // check for short packets
        if (payloadLen < 0) {
            DEBUG_MSG("ignoring received packet too short\n");
            rxBad++;
        } else {
            const PacketHeader *h = (PacketHeader *)radiobuf;
            uint8_t ourAddr = nodeDB.getNodeNum();

            rxGood++;
            if (h->to != 255 && h->to != ourAddr) {
                DEBUG_MSG("ignoring packet not sent to us\n");
            } else {
                MeshPacket *mp = packetPool.allocZeroed();

                mp->from = h->from;
                mp->to = h->to;
                mp->id = h->id;
                addReceiveMetadata(mp);

                mp->which_payload = MeshPacket_encrypted_tag; // Mark that the payload is still encrypted at this point
                assert(payloadLen <= sizeof(mp->encrypted.bytes));
                memcpy(mp->encrypted.bytes, payload, payloadLen);
                mp->encrypted.size = payloadLen;

                DEBUG_MSG("Lora RX interrupt from=0x%x, id=%u\n", mp->from, mp->id);

                deliverToReceiver(mp);
            }
        }
    }
}

/** start an immediate transmit */
void RadioLibInterface::startSend(MeshPacket *txp)
{
    DEBUG_MSG("Starting low level send from=0x%x, id=%u!\n", txp->from, txp->id);
    setStandby(); // Cancel any already in process receives

    size_t numbytes = beginSending(txp);

    int res = iface->startTransmit(radiobuf, numbytes);
    assert(res == ERR_NONE);

    // Must be done AFTER, starting transmit, because startTransmit clears (possibly stale) interrupt pending register bits
    enableInterrupt(isrTxLevel0);
}