Keep dummy clocks in SCLK (SPI) - arduino

Question

I'm using ESP32 on VSPI in a half-duplex manner with a slave device.
I wish to first send the device a standard SPI transaction, and right after that to keep clocking out dummy pulses in the same VSPI interface (clocking VSPICLK pin with same frequency, with zeros on VSPID).
I managed to send the transaction itself, but I don't find the right way to keep the dummy clocks. Important to mention that the dummy pulses shouldn't block the code so I can handle other tasks.
Any thoughts?
Update:
Getting closer by calling a simple write bytes method
/**
* #param data uint8_t *
* #param size uint32_t
*/
void SPIClass::writeBytes(const uint8_t * data, uint32_t size)
{
if(_inTransaction){
return spiWriteNL(_spi, data, size);
}
spiSimpleTransaction(_spi);
spiWriteNL(_spi, data, size);
spiEndTransaction(_spi);
}
But this one blocks...
Previously:
I've tries to send empty bytes in a normal SPI transaction but this is a blocking method and got some lags between bytes (you can see it in the VSCLK blue channel).
dummy clocks with lags, and blocking code
void write(uint8_t data)
{
noInterrupts();
// Working transaction to the device
// _spi_dev is an SPIClass*
_spi_dev->beginTransaction();
_spi_dev->transfer(data);
_spi_dev->endTransaction();
delayMicroseconds(10); // Required delay by the slave device to latch the command
// naively sending dummy bytes - a blocking call
_spi_dev->beginTransaction();
for (uint8_t n = 0; n < 100; n++) {
for (int8_t c = 10; c > 0; c--) _spi_dev->transfer(0x0);
}
_spi_dev->endTransaction();
interrupts();
}
This code:
_spi_dev->transfer(data);
ends up with this:
uint8_t spiTransferByte(spi_t * spi, uint8_t data)
{
if(!spi) {
return 0;
}
SPI_MUTEX_LOCK();
spi->dev->mosi_dlen.usr_mosi_dbitlen = 7;
spi->dev->miso_dlen.usr_miso_dbitlen = 7;
spi->dev->data_buf[0] = data;
#if CONFIG_IDF_TARGET_ESP32C3
spi->dev->cmd.update = 1;
while (spi->dev->cmd.update);
#endif
spi->dev->cmd.usr = 1;
while(spi->dev->cmd.usr);
data = spi->dev->data_buf[0] & 0xFF;
SPI_MUTEX_UNLOCK();
return data;
}
In Addition this one:
_spi_dev->beginTransaction();
With this:
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;
}