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KL26Z UART with DMA Tx fails with baud > 115200

Question asked by geoffs on Feb 13, 2017
Latest reply on Feb 21, 2017 by Jorge Antonio Alcala Vazquez

I have been looking into a problem with using DMA transfers with the UART on a FRDM-KL26Z development board.  I have replicated the problem using one of the driver sample codes for the Kinetis SDK v2.


The example code is located in the following directory of the KSDK v2 folder:



This code builds and runs just fine with the default baud rate of 115,200 bps.  However changing the baud rate to the next highest standard value of 230,400 bps results in a hard fault when attempting to enable the UART Tx DMA.  I have traced the hard fault back to where a KSDK library function (UART_EnableTxDMA() in fsl_uart.h) attempts to set the Transmitter DMA Select bit "TDMAS" in the UART1_C4 register.


Is this expected behaviour ?  My reading of the KL26Z reference manual and other information suggests UART DMA transfers should be capable of much higher speeds.