Microblaze MCS I/O Module Uart Rx Interrupt Example and bug in xiomodule_uart_intr.c

uart_test

#include <stdio.h>
#include "xiomodule.h"
#include "xiomodule_l.h"
#include "xparameters.h"

void recv_handler(void *CallBackRef, unsigned int ByteCount);

int main()
{
    XIOModule io;

    microblaze_enable_interrupts();
    microblaze_register_handler(XIOModule_DeviceInterruptHandler, XPAR_IOMODULE_0_DEVICE_ID);

    XIOModule_Initialize(&io, XPAR_IOMODULE_0_DEVICE_ID);
    XIOModule_SetRecvHandler(&io, recv_handler, &io);
    XIOModule_Uart_EnableInterrupt(&io);
    XIOModule_Connect(&io, XIN_IOMODULE_UART_RX_INTERRUPT_INTR, (XInterruptHandler)XIOModule_Uart_InterruptHandler, &io);
    XIOModule_Start(&io);

    while (1);
}


void recv_handler(void *CallBackRef, unsigned int ByteCount) {
	xil_printf("uart interrupt");
}

xiomodule_uart_intr.c:XIOModule_Uart_InterruptHandler()

...

/**
*
* This function is the interrupt handler for the UART.
* It must be connected to an interrupt system by the user such that it is
* called when an interrupt for any UART lite occurs. This function
* does not save or restore the processor context such that the user must
* ensure this occurs.
*
* @param	InstancePtr contains a pointer to the instance of the IOModule
*		that the interrupt is for.
*
* @return	None.
*
* @note		None.
*
******************************************************************************/
void XIOModule_Uart_InterruptHandler(XIOModule *InstancePtr)
{
	u32 IsrStatus;

	Xil_AssertVoid(InstancePtr != NULL);

	/*
	 * Read the status register to determine which, could be both,
	 * interrupt is active
	 */
	
	/*
	 * BUG:
	 *
	 * In the original code, the I/O Module's Interrupt Pedning Register 0x00000034 was 
	 * read instead of the UART Status Register, causing the handlers never to be called.
	 *
	 * 	IsrStatus = XIOModule_ReadReg(InstancePtr->BaseAddress,
	 *				XIN_IPR_OFFSET);
	 * The followoing works:
	 */
	IsrStatus = XIOModule_ReadReg(InstancePtr->BaseAddress,
					XUL_STATUS_REG_OFFSET);

	if ((IsrStatus & XUL_SR_RX_FIFO_VALID_DATA) != 0) {
		ReceiveDataHandler(InstancePtr);
	}

	if (((IsrStatus & XUL_SR_TX_FIFO_FULL) == XUL_SR_TX_FIFO_FULL) &&
		(InstancePtr->SendBuffer.RequestedBytes > 0)) {
		SendDataHandler(InstancePtr);
	}
}

...

See http://forums.xilinx.com/t5/Embedded-Development-Tools/Bug-Solution-for-Microblaze-MCS-I-O-Module-UART-Interrupt-driver/td-p/598484