| The purpose of this test is to validate that uart_poll_out call is resilient to |
| being interrupted by another uart API call. That includes uart_poll_out called |
| from higher priority context, uart_fifo_fill called from UART interrupt context |
| and uart_tx called from higher priority context. Preemptions shall not lead to |
| any bytes being dropped. |
| |
| This test is establishing 3 context from which uart_poll_out is called: |
| - main thread |
| - higher priority thread |
| - k_timer timeout context |
| |
| From each context stream of data is being sent. Bytes in streams are encoded as |
| following: 4 MSB bits contains stream ID, 4 LSB bits are incremented. |
| |
| Test requires that two pairs of pins are shortened: TX with RX and CTS with RTS. |
| UART receives loopback data and validates if for each stream (identified by ID) |
| data is consistent. |
