Xilinx Vivado Design Suite 16.2 and Embedded Processing Using Microblaze with BASYS3 Old

Example: MB_16p2_07_PeripheralTestWorks

This design works and does the peripheral test over the UART. Unlike the example below, the "reset" issue was finally fixed by setting the "reset" in from the board to an active high and using the Locked output from the Clocking Wizard for the Processor System Reset ext_reset_in. (Creating the design was similar to the steps outlined below, except for these changes mentioned which were done after verifying the design.) The Microblaze uses 32 kB memory but no cache.

The design wrapper is given below:

module design_1_wrapper

(dip_switches_16bits_tri_i,

led_16bits_tri_o,

reset,

sys_clock,

usb_uart_rxd,

usb_uart_txd);

input [15:0]dip_switches_16bits_tri_i;

output [15:0]led_16bits_tri_o;

input reset;

input sys_clock;

input usb_uart_rxd;

output usb_uart_txd;

wire [15:0]dip_switches_16bits_tri_i;

wire [15:0]led_16bits_tri_o;

wire reset;

wire sys_clock;

wire usb_uart_rxd;

wire usb_uart_txd;

design_1 design_1_i

(.dip_switches_16bits_tri_i(dip_switches_16bits_tri_i),

.led_16bits_tri_o(led_16bits_tri_o),

.reset(reset),

.sys_clock(sys_clock),

.usb_uart_rxd(usb_uart_rxd),

.usb_uart_txd(usb_uart_txd));

endmodule

The modified SDK files are shown below. (The original files created by SDK did not include the GPIO led_16bits. I added the changes to include the GPIO output.)

#include <stdio.h>

#include "xparameters.h"

#include "xil_cache.h"

#include "xgpio.h"

#include "gpio_header.h"

int main()

{

Xil_ICacheEnable();

Xil_DCacheEnable();

print("---Entering main---\n\r");

{

u32 status;

print("\r\nRunning GpioInputExample() for axi_gpio_0...\r\n");

u32 DataRead;

status = GpioInputExample(XPAR_AXI_GPIO_0_DEVICE_ID, &DataRead);

if (status == 0) {

xil_printf("GpioInputExample PASSED. Read data:0x%X\r\n", DataRead);

}

else {

print("GpioInputExample FAILED.\r\n");

}

status = GpioOutputExample(XPAR_AXI_GPIO_0_DEVICE_ID, 16);

if (status == 0) {

xil_printf("GpioOutputExample PASSED. Read data:0x%X\r\n", DataRead);

}

else {

print("GpioOutputExample FAILED.\r\n");

}

}

print("---Exiting main---\n\r");

Xil_DCacheDisable();

Xil_ICacheDisable();

return 0;

}

Also the xgpio_tapp_example file was modified to accomodate the two different GPIO channels, "1" for input and "2" for output. See the added / modified code snippet from this file:

#define LED_CHANNEL 2

#define LED_CHANNELIN 1

int GpioInputExample(u16 DeviceId, u32 *DataRead)

{

int Status;

/*

* Initialize the GPIO driver so that it's ready to use,

* specify the device ID that is generated in xparameters.h

*/

Status = XGpio_Initialize(&GpioInput, DeviceId);

if (Status != XST_SUCCESS) {

return XST_FAILURE;

}

/* Set the direction for all signals to be inputs */

XGpio_SetDataDirection(&GpioInput, LED_CHANNELIN, 0xFFFFFFFF);

/* Read the state of the data so that it can be verified */

*DataRead = XGpio_DiscreteRead(&GpioInput, LED_CHANNELIN);

//New try this! Seems to work

// XGpio_DiscreteWrite(&GpioInput, 2, 0xff);

return XST_SUCCESS;

}

Reset and Clock Wizard Settings

The design only worked after using the "reset" settings shown above, i.e., reset active high and only connected to Clocking Wizard and not to the Processor System Reset's ext_reset_in. With the settings shown below (which are similar to the sample Xilinx design, however these are Active High), the reset button must be pressed for the entire program execution.

By default, reset on the BASYS3 board is LO; pressing it makes it go HI.

The scope screen shot below shows what happens when reset is first pushed:

Channel 1: (Top) is the "reset" button being pushed and going high

Channel 2: is is Clocking Wizard's "locked" output going low because of the reset

Channel 3: is the sys_clock which is not affected by this

Channel 4; (Bottom) is the Clocking Wizard's "clk_out1" which is terminated because of the reset.