Add TWAI support for ESP32 and ESP32-S2

[jessebraham]

While this builds, unfortunately I have not yet gotten it to actually work. Just opening a draft in case somebody else feels like taking a look at it in the meantime. Hoping to dig into this next week, though.

[Dazza0]

@jessebraham For ESP32 ECO2 or later revisions, in fn set_baud_rate() we may want to set the interrupt_enable_reg.brp_div field to 0 explicitly. Else, we risk the operating baud rate of the TWAI peripheral to be half of what is specified.

In early versions of the ESP32 (i.e., ECO0 and ECO1), the bus_timing_0_reg.brp field was only 6-bits wide. Assuming an input APB clock of 80MHz and the bit timing configuration below, the lowest achievable bit rate of TWAI on early ESP32 revisions was limited to 25K.

#define TWAI_TIMING_CONFIG_25KBITS()    {.quanta_resolution_hz = 625000, .tseg_1 = 16, .tseg_2 = 8, .sjw = 3, .triple_sampling = false}

Thus, to achieve lower bit rates on the ESP32 (without needing to change the bit timing register), in later versions of the ESP32 (i.e. ECO2 and ECO3) we added the interrupt_enable_reg.brp_div. If set, this bit will pre-divide the input APB clock (resulting in an 40MHz input clock) thus allowing lower bit rates to be achieved:

#if (SOC_TWAI_BRP_MAX > 128) || (CONFIG_ESP32_REV_MIN_FULL >= 200)
#define TWAI_TIMING_CONFIG_12_5KBITS()  {.quanta_resolution_hz = 312500, .tseg_1 = 16, .tseg_2 = 8, .sjw = 3, .triple_sampling = false}
#define TWAI_TIMING_CONFIG_16KBITS()    {.quanta_resolution_hz = 400000, .tseg_1 = 16, .tseg_2 = 8, .sjw = 3, .triple_sampling = false}
#define TWAI_TIMING_CONFIG_20KBITS()    {.quanta_resolution_hz = 400000, .tseg_1 = 15, .tseg_2 = 4, .sjw = 3, .triple_sampling = false}
#endif // (SOC_TWAI_BRP_MAX > 128) || (CONFIG_ESP32_REV_MIN_FULL >= 200)

However, I'm not sure if the interrupt_enable_reg.brp_div is reset by default, so it a good idea to clear this bit explicitly. For reference, please take a look at the twai_ll_set_bus_timing() function and the TWAI struct in ESP-IDF.