Conveyor (38-dma-uart-tx)

A telemetry system needs to transmit data buffers over UART without tying up the CPU in a polling loop. Your job: configure DMA2 Stream 7 to transfer a message buffer to USART1's data register automatically.

The starter code provides working UART initialization and helper functions. Your task is to fill in the DMA configuration: enable the DMA clock, set up stream registers, trigger the transfer, and wait for completion.

On the STM32F4, USART1_TX maps to DMA2 Stream 7, Channel 4. The DMA controller lives on AHB1 (RCC AHB1ENR bit 22).

Expected output:

HELLO
STATUS:OK

The first line is transmitted by DMA. The second line is sent via polling after the transfer completes. The DMA configuration registers are also inspected directly, so they must hold correct values.