Update embedded-hal dependencies

[romancardenas]

NOTE: I still haven't tested these updates on boards. I will keep building some examples to verify that everything is alright. Furthermore, I have a few doubts about some peripherals (especially SPI, namely I don't understand why we would support SPI peripherals with MOSI or MISO missing).

[almindor]

NOTE: I still haven't tested these updates on boards. I will keep building some examples to verify that everything is alright. Furthermore, I have a few doubts about some peripherals (especially SPI, namely I don't understand why we would support SPI peripherals with MOSI or MISO missing).

By MOSI/MISO missing I'm guessing you mean using the (MOSI, SCK, CS) kind of tuples? This was done since some devices (e.g. displays) do not use MISO and do not have an actual connector for it.

[romancardenas]

So we provide SPI implementation without owning the MISO pin?

The potential problem I see here is that SPI traits usually deal with reading and writing. Maybe we need to re-structure the trait implementation to return errors in those pin configurations that are not complete (e.g., return an Error when trying to read from a display)

[romancardenas]

I rescued a few examples from riscv-quickstart but adapted them to use semihosting for QEMU emulation. However (surprise) QEMU does not support GPIO on sifive_e targets yet 🥲

In any case, I will try to set up a proper GDB session with semihosting so we can test examples on board. Eventually, QEMU will support our needs and we can start using more robust CI workflows.

[romancardenas]

I added new examples. It looks like QEMU supported GPIOs, but I introduced a bug in the GPIO implementation. Current examples work as expected both in QEMU and on board.

Examples are now in hifive1-examples. The idea is that hifive1-examples can work as riscv-rust-quickstart but with all the new configurations. Having all the examples in the same repo as the PAC, HAL, and BSP is useful while developing.

I managed to use semihosting on the board. However, it only works for OpenOCD, JLinkDebugger has this option disabled.
I added a few scripts to facilitate opening a debug session on board. Once I am done testing everything, I will write a nice README file.

[romancardenas]

I still need to check:

• GPIO input traits
• PWM traits
• I2C traits
• SPI traits