tests: drivers: uart: baudrate_test: Improve accuracy measurement

[nordic-krch]

Test was reporting high deviation 17-25% which seemed high. Such measurement inaccuracy was due to 3 reasons:

• using gpio Zephyr API for reading pin state which is twice longer than using GPIO HAL
• assumption that stop bits are also 0 and should be included in the measurement. UART stop bits are 1 so they should not be included
• starting UART transfer and then starting the measurement. For high baudrates beginning of the byte was not included in the measurement as first gpio read was already 0.

All issues have been fixed:

• Reduced number of bits in the frame (biggest gain).
• Using GPIO HAL for reading the input - sampling frequency is doubled.
• Transferring 2 bytes and measuring the second byte which improved accuracy for higher baudrates.

Additionally, reduced number of repeats from 10 to 3 to shorten the test.

[NordicBuilder]

CI Information

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Build number: 2

Inputs:

Sources:

sdk-nrf: PR head: a24ca615f01723a65d8fc6f75b79b511a8693fa9

more details

sdk-nrf:

PR head: a24ca615f01723a65d8fc6f75b79b511a8693fa9
merge base: 01c741a64db9181ca9914d35efc6bc0ef98003ce
target head (main): 01c741a64db9181ca9914d35efc6bc0ef98003ce
Diff

Github labels

Enabled	Name	Description
	ci-disabled	Disable the ci execution
	ci-all-test	Run all of ci, no test spec filtering will be done
	ci-force-downstream	Force execution of downstream even if twister fails
	ci-run-twister	Force run twister
	ci-run-zephyr-twister	Force run zephyr twister

List of changed files detected by CI (2)

tests
│  ├── drivers
│  │  ├── uart
│  │  │  ├── uart_baudrate_test
│  │  │  │  ├── Kconfig
│  │  │  │  ├── src
│  │  │  │  │  │ main.c

Outputs:

Toolchain

Version: 53ac68dd62
Build docker image: docker-dtr.nordicsemi.no/sw-production/ncs-build:53ac68dd62_5ea73affbf

Test Spec & Results: ✅ Success; ❌ Failure; 🟠 Queued; 🟡 Progress; ◻️ Skipped; ⚠️ Quarantine

• ◻️ Toolchain - Skipped: existing toolchain is used
• ✅ Build twister
  • sdk-nrf test count: 16
• ✅ Integration tests

Disabled integration tests

• • test-fw-nrfconnect-nrf_lrcs_mosh
  • test-fw-nrfconnect-nrf_lrcs_positioning
  • desktop52_verification
  • test_ble_nrf_config
  • test-fw-nrfconnect-apps
  • test-fw-nrfconnect-ble_mesh
  • test-fw-nrfconnect-ble_samples
  • test-fw-nrfconnect-chip
  • test-fw-nrfconnect-fem
  • test-fw-nrfconnect-nfc
  • test-fw-nrfconnect-nrf-iot_libmodem-nrf
  • test-fw-nrfconnect-nrf-iot_lwm2m
  • test-fw-nrfconnect-nrf-iot_samples
  • test-fw-nrfconnect-nrf-iot_thingy91
  • test-fw-nrfconnect-nrf-iot_zephyr_lwm2m
  • test-fw-nrfconnect-nrf_crypto
  • test-fw-nrfconnect-ps-main
  • test-fw-nrfconnect-rpc
  • test-fw-nrfconnect-rs
  • test-fw-nrfconnect-tfm
  • test-fw-nrfconnect-thread-main
  • test-low-level
  • test-sdk-audio
  • test-sdk-dfu
  • test-sdk-find-my
  • test-sdk-mcuboot
  • test-sdk-wifi

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