Copies data from the SPI flash storage into a pre-existing blob
Address from which to copy the data
The blob into which to copy the bytes
The number of bytes to copy
This method reads the specified number of bytes, starting at the given address given, and writes them into the blob passed as the method’s second parameter. The bytes will be written at the current location of the blob’s read/write pointer, which can be determined with the blob.tell() method and set with the blob.seek() method.
Contrast this method with spiflash.read(), which performs the same task but returns the bytes read from the SPI flash as a new blob object.
Build up a pre-existing blob from SPI flash