The has successfully run my loopback self-test program for CAN,
which tests transmission, reception, and filtering. The 1M baud rate setting
was also verified on saleae to be accurate.
I have a function where it should be impossible to reach the end, so I put in a safe-mode reset at the bottom:
```
int find_unused_slot(void) {
// precondition: you already verified that a slot was available
for (int i=0; i<NUM_SLOTS; i++) {
if( slot_free(i)) {
return i;
}
}
safe_mode_reset(MICROPY_FATAL_ERROR);
}
```
However, the compiler still gave a diagnostic, because safe_mode_reset was not declared NORETURN.
So I started by teaching the compiler that reset_into_safe_mode never returned. This leads at least one level deeper due to reset_cpu needing to be a NORETURN function. Each port is a little different in this area. I also marked reset_to_bootloader as NORETURN.
Additional notes:
* stm32's reset_to_bootloader was not implemented, but now does a bare reset. Most stm32s are not fitted with uf2 bootloaders anyway.
* ditto cxd56
* esp32s2 did not implement reset_cpu at all. I used esp_restart(). (not tested)
* litex did not implement reset_cpu at all. I used reboot_ctrl_write. But notably this is what reset_to_bootloader already did, so one or the other must be incorrect (not tested). reboot_ctrl_write cannot be declared NORETURN, as it returns unless the special value 0xac is written), so a new unreachable forever-loop is added.
* cxd56's reset is via a boardctl() call which can't generically be declared NORETURN, so a new unreacahble "for(;;)" forever-loop is added.
* In several places, NVIC_SystemReset is redeclared with NORETURN applied. This is accepted just fine by gcc. I chose this as preferable to editing the multiple copies of CMSIS headers where it is normally declared.
* the stub safe_mode reset simply aborts. This is used in mpy-cross.
This is a slight trade-off with code size, in places where a "_varg"
mp_raise variant is now used. The net savings on trinket_m0 is
just 32 bytes.
It also means that the translation will include the original English
text, and cannot be translated. These are usually names of Python
types such as int, set, or dict or special values such as "inf" or
"Nan".
.. this probably came from the examples that I studied at the beginning
of implementation.
The card detection feature is unused. As a "detect pin" is not
sent from the shared-bindings, there is no way to get the correct pin
anyway. Instead, if code needs to detect the insertion state it can
directly use the pin as GPIO in Python code.
Currently, only the bus specs of the stm32f405xx have been coded.
Other stm-family chips need (at a minimum) the specs added in their
periph.[ch] files.
I discussed with Hierophect on Discord about how to "de-nest" the code
for configuring SPI objects on STM, because the problems with one
nesting level per pin becomes unmanageable with the up to 10 pins of
SDIO.
This code (which is only compile-tested so far) demonstrates the concept
we discussed.
The SCK pin is always required. Loop over all possibilities of the SCK
pin. When we are considering a particular item in the mcu_spi_sck_list
we have now become committed to using a particular periph_index. If all
the other pins can be satisfied by that periph_index, then we have a
working combination. Once we have a working combination that is not
reserved, we can return that combination. On reaching the end, we have
checked all the possible possibilities and can give the same errors as
before: One if there was a possibility that worked but was reserved;
and another if no possibility worked.
Since Actions passed on the previous commit, where this computed value
was checked against the specified value (if any), this is no net change,
except that we no longer need to specify it for particular boards or
ports.
