Enable UARTE1 for 52840 MCUs.

[bjc]

This is mentioned in the datasheet in §4.2 Table 3 (Instantiation
Table) and exists in the PAC for this chipset.

Tested with a nrf52840-mdk board.

[jacobrosenthal]

Checks out on an nrf52840 dk. (and works with #102 with a fix hopefully @korken89 saw https://github.com/korken89/nrf52-hal/pull/1)

One annoying note I hadn't seen before, unlike UARTE0, both the interrupt and the handler are named UARTE1

so with UARTE0 it looks like this

use hal::target::{interrupt, TIMER0 as TIM0, UARTE1 as UARTE0};

    #[interrupt(priority = 2, resources = [RX, TX], spawn = [printer, rx_error])]
    fn UARTE0_UART0() {
    }

but on UARTE1 you have to import UARTE1 as something else

use hal::target::{interrupt, TIMER0 as TIM0, UARTE1 as UARTE1_OTHER};

    #[interrupt(priority = 2, resources = [RX, TX], spawn = [printer, rx_error])]
    fn UARTE1() {
    }

[bjc]

In general, the peripherals and their interrupts share names. The exceptions are the peripherals which share instances (e.g., UART0/UARTE0 share an instance, and the peripherals are named differently, but the interrupt handler is named UARTE0_UART0).

UARTE1 doesn't share any instances with anything else (there is no UART1), so, like most other things, the peripheral and the interrupt have the same name.

I don't use rtfm, so I don't run into this issue. I also only import the $pac::Interrupt enum, so it doesn't conflict with the peripheral name itself (e.g., I refer to the peripheral type as UARTE0, the interrupt as Interrupt::UARTE0_UART0 and the isr is fn UARTE0_UART0() {}).

[korken89]

Hi, is there something blocking this PR?