Buttons communication problem NIOS II

Thanks for helping me. Here is my top level entity :

module niossram (

// inputs:

osc_clk,

reset_n,

button,

// outputs:

flash_ssram_a,

flash_ssram_d,

led,

ssram_adsc_n,

ssram_bw_n,

ssram_bwe_n,

ssram_ce_n,

ssram_clk,

ssram_oe_n

);

input osc_clk;

input reset_n;

input [ 3: 0] button;

output [ 23: 0] flash_ssram_a;

inout [ 31: 0] flash_ssram_d;

output [ 3: 0] led;

output ssram_adsc_n;

output [ 3: 0] ssram_bw_n;

output ssram_bwe_n;

output ssram_ce_n;

output ssram_clk;

output ssram_oe_n;

wire [ 3: 0] led_n;

wire [ 3: 0] button_n;

assign ssram_clk = osc_clk;

assign led = ~led_n;

niossram_sopc niossram_sopc_instance

(

.in_port_to_the_button_pio (button_n),

.adsc_n_to_the_ssram (ssram_adsc_n),

.bw_n_to_the_ssram (ssram_bw_n),

.bwe_n_to_the_ssram (ssram_bwe_n),

.chipenable1_n_to_the_ssram (ssram_ce_n),

.address_to_the_ssram (flash_ssram_a),

.data_to_and_from_the_ssram (flash_ssram_d),

.clk (osc_clk),

.out_port_from_the_led_pio (led_n),

.outputenable_n_to_the_ssram (ssram_oe_n),

.reset_n (reset_n),

);

endmodule