Add a target for the Adafruit Circuit Playground Bluefruit, which is
based on the nRF52840. Adds the necessary code for the machine
package and the json and linker script files in the targets directory.
The machine package code is based on board_circuitplay_express.go,
with modifications made by consulting the wiring diagram on the
adafruit website here:
https://learn.adafruit.com/adafruit-circuit-playground-bluefruit/downloads
Also adds support to the uf2 conversion packacge to set the familyID
field. The Circuit Playground Bluefruit firmware rejects uf2 files
without the family id set to 0xADA52840 (and without the flag specifying
that the family id is present).
UART2 was configured with the wrong SERCOM for the used pins (PB22 and
PB23). However, after changing the SERCOM from 3 to 5 that led to a
conflict with UART1 (used for the on-board WiFi). But the used pins are
also usable from SERCOM 3, so in the end I switched SERCOM5 and SERCOM3
around.
With this change, I was able to get examples/echo working.
These all-caps constants aren't in the Go style, so rename it to
CPUFrequency (which is more aligned with Go style). Additionally, make
it a function so that it is possible to add support for changing the
frequency in the future.
Tested by running `make smoketest`. None of the outputs did change.
This smartwatch doesn't have an on-board debugger, so I picked the one I
was using while getting this smartwatch to run Go programs (the J-Link
EDU Mini).
* machine/samd51: pin method cleanups.
- Use bit-math to select the group in Pin methods.
- Move Pin methods to atsamd51. They are not chip-specific, they apply to the whole atsamd51 family.
- Move the group/pin-id calculation into a helper method.
- Add a Pin.Toggle() method.
Comparing slices against nil currently causes the slice to escape, due
to a limitation in LLVM 8. This leads to lots of unnecessary heap
allocations. With LLVM 9 and some modifications to TinyGo, this should
be fixed. However, this commit is an easy win right now.
Returning an error when both slices are nil is not necessary, when the
check is left out it should just do nothing.
For updating an SPI screen using the st7735 driver, this results in a
~7% performance win.
Instead of configuring machine.I2C0, machine.I2C1, etc. statically,
allow the pins to be set using machine.I2CConfig. This will also
automatically configure the correct pin mode for each pin instead of
having to specify that manually.
The SPI peripheral in the nrf chips support double buffering, which
makes it possible to keep sending continuously. This change introduces
double buffering on the nrf chips, which should improve SPI performance.
Tested on the pca10040 (nrf52832).
Compared to the already supported stm32f103xx "bluepill" board this:
- features 128 KiB flash memory size ("RB" suffix) instead of 64 KiB, see `targets/stm32f103rb.ld`
- has onboard ST-LINK/V2-1 programmer and debugger requiring different OpenOCD configuration file
- uses USART2 connected to ST-LINK/V2-1 debugger as virtual COM port over USB for `putchar()`
- has a user-accessible button besides the reset button
Motivation: The bluepill uses USART1 as UART0 but other boards like the
STM32 Nucleo boards (and disco as well) use USART2 for USB COM port.
To avoid duplication of code the same pattern as in `machine_atsamd21.go`
is applied where only UART-specific code is moved to `board_*.go`.
The SPI frequency is broken since b8c326d710
added I2C interface and changed the unrelated `PCLK2 = HCLK/4` initialization
to `PCLK2 = HCLK/1` (but I2C uses PCLK1 anyways).
This commit changes all baud rate prescalers to be /4 compared to before.
Note: it is not possible to find an equivalent for 125 KHz SPI speed,
it will be too fast (`f = 72 MHz / 256`)
