pw_uart_mcuxpresso#

pw_uart_mcuxpresso implements the pw_uart interface for reading and writing to a UART using the NXP MCUXpresso SDK.

The only implementation currently provided is DmaUartMcuxpresso, which uses DMA transfers to read and write to the UART, minimizing CPU utilization.

Note

For a simpler UART interface, see pw_stream_uart_mcuxpresso.

Setup#

This module requires a little setup:

  1. Use pw_build_mcuxpresso to create a pw_source_set for an MCUXpresso SDK.

  2. Include the debug console component in this SDK definition.

  3. Specify the pw_third_party_mcuxpresso_SDK GN global variable to specify the name of this source set.

  4. Use a target that calls pw_sys_io_mcuxpresso_Init in pw_boot_PreMainInit or similar.

The name of the SDK source set must be set in the “pw_third_party_mcuxpresso_SDK” GN arg

Usage#

DmaUartMcuxpresso example:

 1  constexpr uint32_t kFlexcomm = 0;
 2  const auto kUartBase = USART0;
 3  constexpr uint32_t kBaudRate = 115200;
 4  constexpr uint32_t kUartInstance = 5;
 5  std::array<std::byte, 65536> ring_buffer = {};
 6  constexpr uint32_t kUartRxDmaCh = 0;
 7  constexpr uint32_t kUartTxDmaCh = 1;
 8
 9  uint32_t flexcomm_clock_freq = CLOCK_GetFlexcommClkFreq(kUartInstance);
10
11  const pw::uart::DmaUartMcuxpresso::Config kConfig = {
12      .usart_base = kUartBase,
13      .baud_rate = kBaudRate,
14      .parity = kUSART_ParityDisabled,
15      .stop_bits = kUSART_OneStopBit,
16      .dma_base = DMA0,
17      .rx_dma_ch = kUartRxDmaCh,
18      .tx_dma_ch = kUartTxDmaCh,
19      .rx_input_mux_dmac_ch_request_en =
20          kINPUTMUX_Flexcomm0RxToDmac0Ch0RequestEna,
21      .tx_input_mux_dmac_ch_request_en =
22          kINPUTMUX_Flexcomm0TxToDmac0Ch1RequestEna,
23      .buffer = pw::ByteSpan(ring_buffer),
24      .srcclk = flexcomm_clock_freq,
25  };
26
27  auto uart = pw::uart::DmaUartMcuxpresso{kConfig};
28
29  PW_TRY(uart.Enable());
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