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cpu/sam0_common: Implement time-sharing of SERCOMs
Contribution description
This adds a periph_sercom feature and implementation which periph_i2c, periph_uart, and periph_spi are implemented on top. This allows for sharing a single SERCOM instance to provide multiple serial interfaces (in round-robin time-sharing fashion).
[!NOTE] In practice, a SERCOM can often not be shared if it needs to provide an UART.
Background:
While code using the I2C/SPI APIs is already optimized to share the peripheral with i2c_acquire()/spi_acquire() and i2c_release()/spi_release(), UARTs are typically not shared and most users will not call uart_poweron() and uart_poweroff() to only have the SERCOM in UART mode when actually needed. Worse: For many use cases (such as stdin), the UART will need to be constantly running, as receiving data happens asynchronously at unpredictable points in time.
Testing procedure
make BOARD=adafruit-metro-m4-express flash term -C tests/periph/selftest_shield
2024-11-21 20:29:42,410 # ALL TESTS SUCCEEDED
2024-11-21 20:29:42,395 # main(): This is RIOT! (Version: 2025.01-devel-156-g1baf0-cpu/sam0_common/periph_sercom)
2024-11-21 20:29:42,396 # self-testing peripheral drivers
2024-11-21 20:29:42,396 # ===============================
2024-11-21 20:29:42,396 # Starting test for GPIO at tests/periph/selftest_shield/main.c:350
2024-11-21 20:29:42,396 # [OK]
2024-11-21 20:29:42,397 # Starting test for GPIO at tests/periph/selftest_shield/main.c:372
2024-11-21 20:29:42,397 # [OK]
2024-11-21 20:29:42,397 # Starting test for GPIO at tests/periph/selftest_shield/main.c:402
2024-11-21 20:29:42,397 # [OK]
2024-11-21 20:29:42,397 # Starting test for GPIO at tests/periph/selftest_shield/main.c:432
2024-11-21 20:29:42,397 # (skipped)
2024-11-21 20:29:42,398 # Starting test for GPIO at tests/periph/selftest_shield/main.c:458
2024-11-21 20:29:42,398 # (skipped)
2024-11-21 20:29:42,398 # Starting test for GPIO-IRQ at tests/periph/selftest_shield/main.c:505
2024-11-21 20:29:42,398 # [OK]
2024-11-21 20:29:42,399 # Starting test for GPIO-IRQ at tests/periph/selftest_shield/main.c:571
2024-11-21 20:29:42,399 # [OK]
2024-11-21 20:29:42,399 # Starting test for GPIO-IRQ at tests/periph/selftest_shield/main.c:637
2024-11-21 20:29:42,399 # [OK]
2024-11-21 20:29:42,399 # Starting test for I2C at tests/periph/selftest_shield/main.c:711
2024-11-21 20:29:42,399 # [OK]
2024-11-21 20:29:42,400 # Starting test for UART at tests/periph/selftest_shield/main.c:806
2024-11-21 20:29:42,400 # [OK]
2024-11-21 20:29:42,400 # Starting test for UART at tests/periph/selftest_shield/main.c:815
2024-11-21 20:29:42,400 # [OK]
2024-11-21 20:29:42,400 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,401 # [OK]
2024-11-21 20:29:42,401 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,401 # [OK]
2024-11-21 20:29:42,401 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,401 # [OK]
2024-11-21 20:29:42,402 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,402 # [OK]
2024-11-21 20:29:42,402 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,402 # [OK]
2024-11-21 20:29:42,402 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,402 # [OK]
2024-11-21 20:29:42,403 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,403 # [OK]
2024-11-21 20:29:42,403 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,403 # [OK]
2024-11-21 20:29:42,404 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,404 # [OK]
2024-11-21 20:29:42,404 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,404 # [OK]
2024-11-21 20:29:42,404 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,405 # [OK]
2024-11-21 20:29:42,405 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,405 # [OK]
2024-11-21 20:29:42,405 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,405 # [OK]
2024-11-21 20:29:42,406 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,406 # [OK]
2024-11-21 20:29:42,406 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,406 # [OK]
2024-11-21 20:29:42,406 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,406 # [OK]
2024-11-21 20:29:42,407 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,407 # [OK]
2024-11-21 20:29:42,407 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,407 # [OK]
2024-11-21 20:29:42,408 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,408 # [OK]
2024-11-21 20:29:42,408 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,408 # [OK]
2024-11-21 20:29:42,408 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,408 # [OK]
2024-11-21 20:29:42,409 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,409 # [OK]
2024-11-21 20:29:42,409 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,409 # [OK]
2024-11-21 20:29:42,409 # Starting test for SPI at tests/periph/selftest_shield/main.c:858
2024-11-21 20:29:42,409 # [OK]
2024-11-21 20:29:42,410 # Starting test for ADC at tests/periph/selftest_shield/main.c:1072
2024-11-21 20:29:42,410 # [OK]
2024-11-21 20:29:42,410 #
2024-11-21 20:29:42,410 #
2024-11-21 20:29:42,410 # ALL TESTS SUCCEEDED
2024-11-21 20:29:42,410 # { "threads": [{ "name": "main", "stack_size": 1536, "stack_used": 572}]}
Issues/PRs references
None
Murdock results
:heavy_check_mark: PASSED
bd365b11ffdbe4cf3c119af18ca2d6aa701e350e boards: fix whitespace style issues
| Success | Failures | Total | Runtime |
|---|---|---|---|
| 10248 | 0 | 10249 | 16m:54s |
Artifacts
please reduce static noise
there are multiple warnings like
Check warning on line 122 in boards/arduino-nano-33-iot/include/periph_conf.h
GitHub Actions / static-tests
comma should be followed by whitespace
- .rx_pin = GPIO_PIN(PB,23),
+ .rx_pin = GPIO_PIN(PB, 23),
boards/samd20-xpro/include/periph_conf.h and boards/samd21-xpro/include/periph_conf.h
also miss white space ( i don't know why these messages are not brought up at once but trickel after every commit)
the static test also don't like regular form past tens of irregular "reset"
seems like vera++ produced that noise, i reduced that list to once per file and warning
boards/samd20-xpro/include/periph_conf.h:141: warning: comma should be followed by whitespace
boards/samd21-xpro/include/periph_conf.h:143: warning: comma should be followed by whitespace
boards/samr21-xpro/include/periph_conf.h:165: warning: comma should be followed by whitespace
boards/samr30-xpro/include/periph_conf.h:63: warning: comma should be followed by whitespace
boards/sodaq-autonomo/include/periph_conf.h:45: warning: comma should be followed by whitespace
boards/sodaq-explorer/include/periph_conf.h:41: warning: comma should be followed by whitespace
boards/sodaq-one/include/periph_conf.h:44: warning: comma should be followed by whitespace
boards/sodaq-sara-aff/include/periph_conf.h:61: warning: comma should be followed by whitespace
cpu/cortexm_common/include/cpu.h:95: warning: line is longer than 100 characters
cpu/cortexm_common/include/cpu.h:[24](https://github.com/RIOT-OS/RIOT/actions/runs/12050475159/job/33599437291?pr=21029#step:6:31)4: warning: horizontal tab used
cpu/sam0_common/periph/i2c.c:209: warning: comma should not be preceded by whitespace
cpu/sam0_common/periph/i2c.c:308: warning: full block {} expected in the control structure
cpu/samd21/include/periph_cpu.h:55: warning: too many consecutive empty lines
cpu/saml1x/include/periph_cpu.h:139: warning: line is longer than 100 characters
cpu/saml21/include/periph_cpu.h:198: warning: line is longer than 100 characters
pkg/openwsn/include/openwsn_log.h:72: warning: full block {} expected in the control structure