SPI implement transaction locking

Use transactions to skip mutex locks for reads and writes

cores/esp32/esp32-hal-spi.c

@@ -517,41 +517,24 @@ uint8_t spiTransferByte(spi_t * spi, uint8_t data)
     return data;
 }
 
-uint32_t __spiTranslate16(uint16_t data, bool msb)
+uint32_t __spiTranslate24(uint32_t data)
 {
-    if(msb) {
-        return (data >> 8) | (data << 8);
-    } else {
-        return data;
-    }
-}
-
-uint32_t __spiTranslate24(uint32_t data, bool msb)
-{
-    if(msb) {
     union {
         uint32_t l;
         uint8_t b[4];
     } out;
     out.l = data;
     return out.b[2] | (out.b[1] << 8) | (out.b[0] << 16);
-    } else {
-        return data;
-    }
 }
 
-uint32_t __spiTranslate32(uint32_t data, bool msb)
+uint32_t __spiTranslate32(uint32_t data)
 {
-    if(msb) {
     union {
         uint32_t l;
         uint8_t b[4];
     } out;
     out.l = data;
     return out.b[3] | (out.b[2] << 8) | (out.b[1] << 16) | (out.b[0] << 24);
-    } else {
-        return data;
-    }
 }
 
 void spiWriteWord(spi_t * spi, uint16_t data)
@@ -559,10 +542,13 @@ void spiWriteWord(spi_t * spi, uint16_t data)
     if(!spi) {
         return;
     }
+    if(!spi->dev->ctrl.wr_bit_order){
+        data = (data >> 8) | (data << 8);
+    }
     SPI_MUTEX_LOCK();
     spi->dev->mosi_dlen.usr_mosi_dbitlen = 15;
     spi->dev->miso_dlen.usr_miso_dbitlen = 0;
-    spi->dev->data_buf[0] = __spiTranslate16(data, !spi->dev->ctrl.wr_bit_order);
+    spi->dev->data_buf[0] = data;
     spi->dev->cmd.usr = 1;
     while(spi->dev->cmd.usr);
     SPI_MUTEX_UNLOCK();
@@ -573,14 +559,20 @@ uint16_t spiTransferWord(spi_t * spi, uint16_t data)
     if(!spi) {
         return 0;
     }
+    if(!spi->dev->ctrl.wr_bit_order){
+        data = (data >> 8) | (data << 8);
+    }
     SPI_MUTEX_LOCK();
     spi->dev->mosi_dlen.usr_mosi_dbitlen = 15;
     spi->dev->miso_dlen.usr_miso_dbitlen = 15;
-    spi->dev->data_buf[0] = __spiTranslate16(data, !spi->dev->ctrl.wr_bit_order);
+    spi->dev->data_buf[0] = data;
     spi->dev->cmd.usr = 1;
     while(spi->dev->cmd.usr);
-    data = __spiTranslate16(spi->dev->data_buf[0] & 0xFFFF, !spi->dev->ctrl.rd_bit_order);
+    data = spi->dev->data_buf[0];
     SPI_MUTEX_UNLOCK();
+    if(!spi->dev->ctrl.rd_bit_order){
+        data = (data >> 8) | (data << 8);
+    }
     return data;
 }
 
@@ -589,10 +581,13 @@ void spiWriteLong(spi_t * spi, uint32_t data)
     if(!spi) {
         return;
     }
+    if(!spi->dev->ctrl.wr_bit_order){
+        data = __spiTranslate32(data);
+    }
     SPI_MUTEX_LOCK();
     spi->dev->mosi_dlen.usr_mosi_dbitlen = 31;
     spi->dev->miso_dlen.usr_miso_dbitlen = 0;
-    spi->dev->data_buf[0] = __spiTranslate32(data, !spi->dev->ctrl.wr_bit_order);
+    spi->dev->data_buf[0] = data;
     spi->dev->cmd.usr = 1;
     while(spi->dev->cmd.usr);
     SPI_MUTEX_UNLOCK();
@@ -603,57 +598,21 @@ uint32_t spiTransferLong(spi_t * spi, uint32_t data)
     if(!spi) {
         return 0;
     }
+    if(!spi->dev->ctrl.wr_bit_order){
+        data = __spiTranslate32(data);
+    }
     SPI_MUTEX_LOCK();
     spi->dev->mosi_dlen.usr_mosi_dbitlen = 31;
     spi->dev->miso_dlen.usr_miso_dbitlen = 31;
-    spi->dev->data_buf[0] = __spiTranslate32(data, !spi->dev->ctrl.wr_bit_order);
+    spi->dev->data_buf[0] = data;
     spi->dev->cmd.usr = 1;
     while(spi->dev->cmd.usr);
-    data = __spiTranslate32(spi->dev->data_buf[0], !spi->dev->ctrl.rd_bit_order);
+    data = spi->dev->data_buf[0];
     SPI_MUTEX_UNLOCK();
-    return data;
-}
-
-void spiTransferBits(spi_t * spi, uint32_t data, uint32_t * out, uint8_t bits)
-{
-    if(!spi) {
-        return;
-    }
-
-    if(bits > 32) {
-        bits = 32;
+    if(!spi->dev->ctrl.rd_bit_order){
+        data = __spiTranslate32(data);
     }
-    uint32_t bytes = (bits + 7) / 8;//64 max
-    uint32_t mask = (((uint64_t)1 << bits) - 1) & 0xFFFFFFFF;
-
-    SPI_MUTEX_LOCK();
-    spi->dev->mosi_dlen.usr_mosi_dbitlen = (bits - 1);
-    spi->dev->miso_dlen.usr_miso_dbitlen = (bits - 1);
-    if(bytes == 1) {
-        spi->dev->data_buf[0] = data & mask;
-    } else if(bytes == 2) {
-        spi->dev->data_buf[0] = __spiTranslate16(data & mask, !spi->dev->ctrl.wr_bit_order);
-    } else if(bytes == 3) {
-        spi->dev->data_buf[0] = __spiTranslate24(data & mask, !spi->dev->ctrl.wr_bit_order);
-    } else {
-        spi->dev->data_buf[0] = __spiTranslate32(data & mask, !spi->dev->ctrl.wr_bit_order);
-    }
-    spi->dev->cmd.usr = 1;
-
-    while(spi->dev->cmd.usr);
-
-    if(out) {
-        if(bytes == 1) {
-            *out = spi->dev->data_buf[0] & mask;
-        } else if(bytes == 2) {
-            *out = __spiTranslate16(spi->dev->data_buf[0] & mask, !spi->dev->ctrl.wr_bit_order);
-        } else if(bytes == 3) {
-            *out = __spiTranslate24(spi->dev->data_buf[0] & mask, !spi->dev->ctrl.wr_bit_order);
-        } else {
-            *out = __spiTranslate32(spi->dev->data_buf[0] & mask, !spi->dev->ctrl.wr_bit_order);
-        }
-    }
-    SPI_MUTEX_UNLOCK();
+    return data;
 }
 
 void __spiTransferBytes(spi_t * spi, uint8_t * data, uint8_t * out, uint32_t bytes)
@@ -721,6 +680,320 @@ void spiTransferBytes(spi_t * spi, uint8_t * data, uint8_t * out, uint32_t size)
     SPI_MUTEX_UNLOCK();
 }
 
+/*
+ * Manual Lock Management
+ * */
+
+#define MSB_32_SET(var, val) { uint8_t * d = (uint8_t *)&(val); (var) = d[3] | (d[2] << 8) | (d[1] << 16) | (d[0] << 24); }
+#define MSB_24_SET(var, val) { uint8_t * d = (uint8_t *)&(val); (var) = d[2] | (d[1] << 8) | (d[0] << 16); }
+#define MSB_16_SET(var, val) { (var) = (((val) & 0xFF00) >> 8) | (((val) & 0xFF) << 8); }
+
+void spiTransaction(spi_t * spi, uint32_t clockDiv, uint8_t dataMode, uint8_t bitOrder)
+{
+    if(!spi) {
+        return;
+    }
+    SPI_MUTEX_LOCK();
+    spi->dev->clock.val = clockDiv;
+    switch (dataMode) {
+        case SPI_MODE1:
+            spi->dev->pin.ck_idle_edge = 0;
+            spi->dev->user.ck_out_edge = 1;
+            break;
+        case SPI_MODE2:
+            spi->dev->pin.ck_idle_edge = 1;
+            spi->dev->user.ck_out_edge = 0;
+            break;
+        case SPI_MODE3:
+            spi->dev->pin.ck_idle_edge = 1;
+            spi->dev->user.ck_out_edge = 1;
+            break;
+        case SPI_MODE0:
+        default:
+            spi->dev->pin.ck_idle_edge = 0;
+            spi->dev->user.ck_out_edge = 0;
+            break;
+    }
+    if (SPI_MSBFIRST == bitOrder) {
+        spi->dev->ctrl.wr_bit_order = 0;
+        spi->dev->ctrl.rd_bit_order = 0;
+    } else if (SPI_LSBFIRST == bitOrder) {
+        spi->dev->ctrl.wr_bit_order = 1;
+        spi->dev->ctrl.rd_bit_order = 1;
+    }
+}
+
+void spiSimpleTransaction(spi_t * spi)
+{
+    if(!spi) {
+        return;
+    }
+    SPI_MUTEX_LOCK();
+}
+
+void spiEndTransaction(spi_t * spi)
+{
+    if(!spi) {
+        return;
+    }
+    SPI_MUTEX_UNLOCK();
+}
+
+void spiWriteByteNL(spi_t * spi, uint8_t data)
+{
+    if(!spi) {
+        return;
+    }
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = 7;
+    spi->dev->miso_dlen.usr_miso_dbitlen = 0;
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+}
+
+uint8_t spiTransferByteNL(spi_t * spi, uint8_t data)
+{
+    if(!spi) {
+        return 0;
+    }
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = 7;
+    spi->dev->miso_dlen.usr_miso_dbitlen = 7;
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+    data = spi->dev->data_buf[0] & 0xFF;
+    return data;
+}
+
+void spiWriteShortNL(spi_t * spi, uint16_t data)
+{
+    if(!spi) {
+        return;
+    }
+    if(!spi->dev->ctrl.wr_bit_order){
+        MSB_16_SET(data, data);
+    }
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = 15;
+    spi->dev->miso_dlen.usr_miso_dbitlen = 0;
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+}
+
+uint16_t spiTransferShortNL(spi_t * spi, uint16_t data)
+{
+    if(!spi) {
+        return 0;
+    }
+    if(!spi->dev->ctrl.wr_bit_order){
+        MSB_16_SET(data, data);
+    }
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = 15;
+    spi->dev->miso_dlen.usr_miso_dbitlen = 15;
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+    data = spi->dev->data_buf[0] & 0xFFFF;
+    if(!spi->dev->ctrl.rd_bit_order){
+        MSB_16_SET(data, data);
+    }
+    return data;
+}
+
+void spiWriteLongNL(spi_t * spi, uint32_t data)
+{
+    if(!spi) {
+        return;
+    }
+    if(!spi->dev->ctrl.wr_bit_order){
+        MSB_32_SET(data, data);
+    }
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = 31;
+    spi->dev->miso_dlen.usr_miso_dbitlen = 0;
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+}
+
+uint32_t spiTransferLongNL(spi_t * spi, uint32_t data)
+{
+    if(!spi) {
+        return 0;
+    }
+    if(!spi->dev->ctrl.wr_bit_order){
+        MSB_32_SET(data, data);
+    }
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = 31;
+    spi->dev->miso_dlen.usr_miso_dbitlen = 31;
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+    data = spi->dev->data_buf[0];
+    if(!spi->dev->ctrl.rd_bit_order){
+        MSB_32_SET(data, data);
+    }
+    return data;
+}
+
+void spiWriteNL(spi_t * spi, const void * data_in, size_t len){
+    size_t longs = len >> 2;
+    if(len & 3){
+        longs++;
+    }
+    uint32_t * data = (uint32_t*)data_in;
+    size_t c_len = 0, c_longs = 0;
+
+    while(len){
+        c_len = (len>64)?64:len;
+        c_longs = (longs > 16)?16:longs;
+
+        spi->dev->mosi_dlen.usr_mosi_dbitlen = (c_len*8)-1;
+        spi->dev->miso_dlen.usr_miso_dbitlen = 0;
+        for (int i=0; i<c_longs; i++) {
+            spi->dev->data_buf[i] = data[i];
+        }
+        spi->dev->cmd.usr = 1;
+        while(spi->dev->cmd.usr);
+
+        data += c_longs;
+        longs -= c_longs;
+        len -= c_len;
+    }
+}
+
+void spiTransferBytesNL(spi_t * spi, const void * data_in, uint8_t * data_out, size_t len){
+    if(!spi) {
+        return;
+    }
+    size_t longs = len >> 2;
+    if(len & 3){
+        longs++;
+    }
+    uint32_t * data = (uint32_t*)data_in;
+    uint32_t * result = (uint32_t*)data_out;
+    size_t c_len = 0, c_longs = 0;
+
+    while(len){
+        c_len = (len>64)?64:len;
+        c_longs = (longs > 16)?16:longs;
+
+        spi->dev->mosi_dlen.usr_mosi_dbitlen = (c_len*8)-1;
+        spi->dev->miso_dlen.usr_miso_dbitlen = (c_len*8)-1;
+        if(data){
+            for (int i=0; i<c_longs; i++) {
+                spi->dev->data_buf[i] = data[i];
+            }
+        } else {
+            for (int i=0; i<c_longs; i++) {
+                spi->dev->data_buf[i] = 0xFFFFFFFF;
+            }
+        }
+        spi->dev->cmd.usr = 1;
+        while(spi->dev->cmd.usr);
+        if(result){
+            for (int i=0; i<c_longs; i++) {
+                result[i] = spi->dev->data_buf[i];
+            }
+        }
+        if(data){
+            data += c_longs;
+        }
+        if(result){
+            result += c_longs;
+        }
+        longs -= c_longs;
+        len -= c_len;
+    }
+}
+
+void spiTransferBitsNL(spi_t * spi, uint32_t data, uint32_t * out, uint8_t bits)
+{
+    if(!spi) {
+        return;
+    }
+
+    if(bits > 32) {
+        bits = 32;
+    }
+    uint32_t bytes = (bits + 7) / 8;//64 max
+    uint32_t mask = (((uint64_t)1 << bits) - 1) & 0xFFFFFFFF;
+    data = data & mask;
+    if(!spi->dev->ctrl.wr_bit_order){
+        if(bytes == 2) {
+            MSB_16_SET(data, data);
+        } else if(bytes == 3) {
+            MSB_24_SET(data, data);
+        } else {
+            MSB_32_SET(data, data);
+        }
+    }
+
+    spi->dev->mosi_dlen.usr_mosi_dbitlen = (bits - 1);
+    spi->dev->miso_dlen.usr_miso_dbitlen = (bits - 1);
+    spi->dev->data_buf[0] = data;
+    spi->dev->cmd.usr = 1;
+    while(spi->dev->cmd.usr);
+    data = spi->dev->data_buf[0];
+    if(out) {
+        *out = data;
+        if(!spi->dev->ctrl.rd_bit_order){
+            if(bytes == 2) {
+                MSB_16_SET(*out, data);
+            } else if(bytes == 3) {
+                MSB_24_SET(*out, data);
+            } else {
+                MSB_32_SET(*out, data);
+            }
+        }
+    }
+}
+
+void spiWritePixelsNL(spi_t * spi, const void * data_in, size_t len){
+    size_t longs = len >> 2;
+    if(len & 3){
+        longs++;
+    }
+    bool msb = !spi->dev->ctrl.wr_bit_order;
+    uint32_t * data = (uint32_t*)data_in;
+    size_t c_len = 0, c_longs = 0, l_bytes = 0;
+
+    while(len){
+        c_len = (len>64)?64:len;
+        c_longs = (longs > 16)?16:longs;
+        l_bytes = (c_len & 3);
+
+        spi->dev->mosi_dlen.usr_mosi_dbitlen = (c_len*8)-1;
+        spi->dev->miso_dlen.usr_miso_dbitlen = 0;
+        for (int i=0; i<c_longs; i++) {
+            if(msb){
+                if(l_bytes && i == (c_longs - 1)){
+                    if(l_bytes == 2){
+                        MSB_16_SET(spi->dev->data_buf[i], data[i]);
+                    } else {
+                        spi->dev->data_buf[i] = data[i] & 0xFF;
+                    }
+                } else {
+                    MSB_32_SET(spi->dev->data_buf[i], data[i]);
+                }
+            } else {
+                spi->dev->data_buf[i] = data[i];
+            }
+        }
+        spi->dev->cmd.usr = 1;
+        while(spi->dev->cmd.usr);
+
+        data += c_longs;
+        longs -= c_longs;
+        len -= c_len;
+    }
+}
+
+
+
+/*
+ * Clock Calculators
+ *
+ * */
 
 typedef union {
     uint32_t regValue;
@@ -795,5 +1068,3 @@ uint32_t spiFrequencyToClockDiv(uint32_t freq)
     return bestReg.regValue;
 }
 
-
-

cores/esp32/esp32-hal-spi.h

@@ -85,12 +85,15 @@ void spiSSClear(spi_t * spi);
 void spiWaitReady(spi_t * spi);
 
 uint32_t spiGetClockDiv(spi_t * spi);
-void spiSetClockDiv(spi_t * spi, uint32_t clockDiv);
-
 uint8_t spiGetDataMode(spi_t * spi);
-void spiSetDataMode(spi_t * spi, uint8_t dataMode);
-
 uint8_t spiGetBitOrder(spi_t * spi);
+
+
+/*
+ * Non transaction based lock methods (each locks and unlocks when called)
+ * */
+void spiSetClockDiv(spi_t * spi, uint32_t clockDiv);
+void spiSetDataMode(spi_t * spi, uint8_t dataMode);
 void spiSetBitOrder(spi_t * spi, uint8_t bitOrder);
 
 void spiWrite(spi_t * spi, uint32_t *data, uint8_t len);
@@ -102,10 +105,32 @@ void spiTransfer(spi_t * spi, uint32_t *out, uint8_t len);
 uint8_t spiTransferByte(spi_t * spi, uint8_t data);
 uint16_t spiTransferWord(spi_t * spi, uint16_t data);
 uint32_t spiTransferLong(spi_t * spi, uint32_t data);
-
-void spiTransferBits(spi_t * spi, uint32_t data, uint32_t * out, uint8_t bits);
 void spiTransferBytes(spi_t * spi, uint8_t * data, uint8_t * out, uint32_t size);
+void spiTransferBits(spi_t * spi, uint32_t data, uint32_t * out, uint8_t bits);
 
+/*
+ * New (EXPERIMENTAL) Transaction lock based API (lock once until endTransaction)
+ * */
+void spiTransaction(spi_t * spi, uint32_t clockDiv, uint8_t dataMode, uint8_t bitOrder);
+void spiSimpleTransaction(spi_t * spi);
+void spiEndTransaction(spi_t * spi);
+
+void spiWriteNL(spi_t * spi, const void * data, uint32_t len);
+void spiWriteByteNL(spi_t * spi, uint8_t data);
+void spiWriteShortNL(spi_t * spi, uint16_t data);
+void spiWriteLongNL(spi_t * spi, uint32_t data);
+void spiWritePixelsNL(spi_t * spi, const void * data, uint32_t len);
+
+#define spiTransferNL(spi, data, len) spiTransferBytesNL(spi, data, data, len)
+uint8_t spiTransferByteNL(spi_t * spi, uint8_t data);
+uint16_t spiTransferShortNL(spi_t * spi, uint16_t data);
+uint32_t spiTransferLongNL(spi_t * spi, uint32_t data);
+void spiTransferBytesNL(spi_t * spi, const void * data_in, uint8_t * data_out, uint32_t len);
+void spiTransferBitsNL(spi_t * spi, uint32_t data_in, uint32_t * data_out, uint8_t bits);
+
+/*
+ * Helper functions to translate frequency to clock divider and back
+ * */
 uint32_t spiFrequencyToClockDiv(uint32_t freq);
 uint32_t spiClockDivToFrequency(uint32_t freq);
 

libraries/SPI/src/SPI.cpp

@@ -31,6 +31,7 @@ SPIClass::SPIClass(uint8_t spi_bus)
     ,_ss(-1)
     ,_div(0)
     ,_freq(1000000)
+    , _inTransaction(false)
 {}
 
 void SPIClass::begin(int8_t sck, int8_t miso, int8_t mosi, int8_t ss)
@@ -84,16 +85,6 @@ void SPIClass::setHwCs(bool use)
     _use_hw_ss = use;
 }
 
-void SPIClass::beginTransaction(SPISettings settings)
-{
-    spiWaitReady(_spi);
-    setFrequency(settings._clock);
-    setBitOrder(settings._bitOrder);
-    setDataMode(settings._dataMode);
-}
-
-void SPIClass::endTransaction() {}
-
 void SPIClass::setFrequency(uint32_t freq)
 {
     //check if last freq changed
@@ -121,38 +112,79 @@ void SPIClass::setBitOrder(uint8_t bitOrder)
     spiSetBitOrder(_spi, bitOrder);
 }
 
+void SPIClass::beginTransaction(SPISettings settings)
+{
+    //check if last freq changed
+    uint32_t cdiv = spiGetClockDiv(_spi);
+    if(_freq != settings._clock || _div != cdiv) {
+        _freq = settings._clock;
+        _div = spiFrequencyToClockDiv(_freq);
+    }
+    spiTransaction(_spi, _div, settings._dataMode, settings._bitOrder);
+    _inTransaction = true;
+}
+
+void SPIClass::endTransaction()
+{
+    if(_inTransaction){
+        spiEndTransaction(_spi);
+        _inTransaction = false;
+    }
+}
+
 void SPIClass::write(uint8_t data)
 {
+    if(_inTransaction){
+        return spiWriteByteNL(_spi, data);
+    }
     spiWriteByte(_spi, data);
 }
 
 uint8_t SPIClass::transfer(uint8_t data)
 {
+    if(_inTransaction){
+        return spiTransferByteNL(_spi, data);
+    }
     return spiTransferByte(_spi, data);
 }
 
 void SPIClass::write16(uint16_t data)
 {
+    if(_inTransaction){
+        return spiWriteShortNL(_spi, data);
+    }
     spiWriteWord(_spi, data);
 }
 
 uint16_t SPIClass::transfer16(uint16_t data)
 {
+    if(_inTransaction){
+        return spiTransferShortNL(_spi, data);
+    }
     return spiTransferWord(_spi, data);
 }
 
 void SPIClass::write32(uint32_t data)
 {
+    if(_inTransaction){
+        return spiWriteLongNL(_spi, data);
+    }
     spiWriteLong(_spi, data);
 }
 
 uint32_t SPIClass::transfer32(uint32_t data)
 {
+    if(_inTransaction){
+        return spiTransferLongNL(_spi, data);
+    }
     return spiTransferLong(_spi, data);
 }
 
 void SPIClass::transferBits(uint32_t data, uint32_t * out, uint8_t bits)
 {
+    if(_inTransaction){
+        return spiTransferBitsNL(_spi, data, out, bits);
+    }
     spiTransferBits(_spi, data, out, bits);
 }
 
@@ -165,7 +197,12 @@ void SPIClass::transferBits(uint32_t data, uint32_t * out, uint8_t bits)
  */
 void SPIClass::writeBytes(uint8_t * data, uint32_t size)
 {
-    spiTransferBytes(_spi, data, 0, size);
+    if(_inTransaction){
+        return spiWriteNL(_spi, data, size);
+    }
+    spiSimpleTransaction(_spi);
+    spiWriteNL(_spi, data, size);
+    spiEndTransaction(_spi);
 }
 
 /**
@@ -175,6 +212,9 @@ void SPIClass::writeBytes(uint8_t * data, uint32_t size)
  */
 void SPIClass::transferBytes(uint8_t * data, uint8_t * out, uint32_t size)
 {
+    if(_inTransaction){
+        return spiTransferBytesNL(_spi, data, out, size);
+    }
     spiTransferBytes(_spi, data, out, size);
 }
 

libraries/SPI/src/SPI.h

@@ -36,6 +36,19 @@ public:
 
 class SPIClass
 {
+private:
+    int8_t _spi_num;
+    spi_t * _spi;
+    bool _use_hw_ss;
+    int8_t _sck;
+    int8_t _miso;
+    int8_t _mosi;
+    int8_t _ss;
+    uint32_t _div;
+    uint32_t _freq;
+    bool _inTransaction;
+    void writePattern_(uint8_t * data, uint8_t size, uint8_t repeat);
+
 public:
     SPIClass(uint8_t spi_bus=HSPI);
     void begin(int8_t sck=-1, int8_t miso=-1, int8_t mosi=-1, int8_t ss=-1);
@@ -61,17 +74,8 @@ public:
     void write32(uint32_t data);
     void writeBytes(uint8_t * data, uint32_t size);
     void writePattern(uint8_t * data, uint8_t size, uint32_t repeat);
-private:
-    int8_t _spi_num;
-    spi_t * _spi;
-    bool _use_hw_ss;
-    int8_t _sck;
-    int8_t _miso;
-    int8_t _mosi;
-    int8_t _ss;
-    uint32_t _div;
-    uint32_t _freq;
-    void writePattern_(uint8_t * data, uint8_t size, uint8_t repeat);
+
+    spi_t * bus(){ return _spi; }
 };
 
 extern SPIClass SPI;