This patch adds support to mboot for programming external SPI flash. It
allows SPI flash to be programmed via a USB DFU utility in the same way
that internal MCU flash is programmed.
Prior to this patch the QSPI driver assumed that the length of all data
reads and writes was a multiple of 4. This patch allows any length. Reads
are optimised for speed by using 32-bit transfers when possible, but writes
always use a byte transfer because they only use a single data IO line and
are relatively slow.
These examples rely on machine and pyb modules, so they have to get.
Leaving 3 BLE examples that also rely on those modules, but can be
fixed to use CP's modules.
This commit cleans up the pin generation code, all the pins and their
AF (only ADC, for now) are specified in nrf52_af.csv and board use their
own csv file to specify which pins are available on that board and if
they have any special names.
With the only difference between a SD and non-SD build is the linker
file, there's no need to have two separate .mk per board files,
just use a conditional.
The DMA peripheral is limited to transferring 65535 elements at a time so
in order to send more than that the SPI driver must split the transfers up.
The user must be aware of this limit if they are relying on precise timing
of the entire SPI transfer, because there might be a small delay between
the split transfers.
Fixes issue #3851, and thanks to @kwagyeman for the original fix.
This behaviour of a NULL write C method on a stream that uses the write
adaptor objects is no longer supported. It was only ever used by the
coverage build for testing the fail path of mp_get_stream_raise().
If the user button is held down indefinitely (eg unintenionally, or because
the GPIO signal of the user button is connected to some external device)
then it makes sense to end the reset mode cycle with the default mode of
1, which executes code as normal.
