High-speed ADC9226 Acquisition Experiment – Xilinx Risc-V Board FII-PRX100 Experiment 19

October 3, 2020 SteveGuysAD acquisition sub-module, ADC9226 Acquisition Experiment

Experiment 19 High-speed ADC9226 Acquisition Experiment

19.1 Experiment Objective

Learn about parallel ADC collectors and master the use of ADC9226.

19.2 Experiment Implement

1. Insert the ADC9226 module face up into the FPGA development board to the GPIO2 and GPIO1 ports which are next to the red-green audio module. Write programs to use this module to test

19.3 Experiment

19.3.1 ADC9226 Module Introduction

ADC9226 module adopts AD9226 chip design of ADI Company. This chip is a monolithic, 12-bit, 65 MSPS analog-to-digital converter (ADC). It uses a single power supply and has an on-chip high-performance sample-and-hold amplifier and voltage reference. It uses a multistage differential pipelined architecture with a data rate of 65 MSPS and guarantees no missing codes over the full operating temperature range.

See Figure 19.1 for ADC9226 timing diagram.

Figure19.1 ADC9226 timing diagram

From this timing diagram, we know that there is no need to configure the AD9226 chip, as long as the appropriate CLOCK is provided, the chip can perform data acquisition.

19.3.2 Program Design

1. AD acquisition sub-module

As can be seen from Figure 19.1, the high bit of AD9226 is bit[0] and the low bit is bit [11], so the data bit order needs to be reversed in the program.

module ad_9226(

input ad_clk,

input [11:0] ad1_in,

output reg [11:0] ad_ch

);

always @(posedge ad_clk)

begin

ad_ch[11] <= ad1_in[0] ;

ad_ch[10] <= ad1_in[1] ;

ad_ch[9 ] <= ad1_in[2] ;

ad_ch[8 ] <= ad1_in[3] ;

ad_ch[7 ] <= ad1_in[4] ;

ad_ch[6 ] <= ad1_in[5] ;

ad_ch[5 ] <= ad1_in[6] ;

ad_ch[4 ] <= ad1_in[7] ;

ad_ch[3 ] <= ad1_in[8] ;

ad_ch[2 ] <= ad1_in[9] ;

ad_ch[1 ] <= ad1_in[10] ;

ad_ch[0 ] <= ad1_in[11] ;

end

endmodule

2.Data conversion program

The AD9226 module design uses an internal reference source. VREF is the output port of the reference source, which can be used for 1V and 2V reference voltages. It can be selected through SENCE. When SENCE is grounded, a 2V reference is provided, and when SENCE is connected to VREF, a 1V reference is provided. The module uses a 2V reference power supply. VINA input range is 1.0 ~ 3.0V.

The 22 pin of AD9226 has the function of collecting data selection. There are two input and output data formats of AD9226. For the specific format, refer to the 9226 datasheet. The 22 pin of the AD9226 module in this experiment is connected to high level, so it uses Binary Output Mode. The BCD conversion submodule has been introduced in Experiment 8 and is not repeated here.

module volt_cal(

input wire ad_clk,

input wire [11:0] ad_ch1,

output [19:0] ch1_dec,

output reg ch1_sig

);

reg [31:0] ch1_data_reg;

reg [11:0] ch1_reg;

reg [31:0] ch1_vol;

always @(posedge ad_clk)

begin

if(ad_ch1[11]==1’b1) begin

ch1_reg<={1’b0,ad_ch1[10:0]};

ch1_sig <= 0;

end

else begin

ch1_reg<={12’h800-ad_ch1[10:0]};

ch1_sig<=1;

end

always @(posedge ad_clk)

begin

ch1_data_reg<=ch1_reg * 2000;

ch1_vol<=ch1_data_reg >>11;

end

bcd bcd1_ist(

.hex (ch1_vol[15:0]),

.dec (ch1_dec),

.clk (ad_clk)

);

endmodule

9226 module AD acquisition range selection

The attenuation range of the AD acquisition module is divided into gears. Press the UP key on the development board to switch the range.

Table 19.1 Gear shift indication table

Gear comparison table (input voltage percentage)	Corresponding indicator
4%	led0 lit
8%	led0, led1 lit
20%	led0, led1, led2 lit
40%	led0, led1, led2, led2 lit

module range (

input wire clk ,

input wire rst_n ,

input wire key ,

output wire [3:0] led ,

output wire [1:0] scope

);

wire flag_switch ;

key_process key_process_inst(

.clk (clk) ,

.rst_n (rst_n) ,

.key_switch (key) ,

.flag_switch (flag_switch)

);

reg [1:0] scope_st =00 ;

reg [3:0] led_temp =4’he ;

always @ (posedge clk ,negedge rst_n)

begin

if (~rst_n)

begin

scope_st <= 0 ;

led_temp <= 4’he ;

end

else begin

case (scope_st)

0: begin

led_temp <= 4’he ;

if (flag_switch )

scope_st <= 1 ;

end

1: begin

led_temp <= 4’hc ;

if (flag_switch )

scope_st <= 2 ;

end

2: begin

led_temp <= 4’h8 ;

if (flag_switch )

scope_st <= 3 ;

end

3: begin

led_temp <= 4’h0 ;

if (flag_switch )

scope_st <= 0 ;

end

endcase

end

assign led = led_temp ;

assign scope = scope_st ;

endmodule

Main program design

The main program is divided into three sub-programs, which are AD_9226 acquisition module, data conversion calculation module volt_cal, and voltage value segment display module. The segment display part has been introduced in the previous experiment and will not be introduced here.

module high_speed_ad_test(

input wire sys_clk,

input wire otr ,

input wire key_switch ,

input wire sys_rst_n ,

input wire [11:0] ad1_in,

output wire ad1_clk,

output wire [5:0] sel,

output wire [3:0] led ,

output wire cain_a,

output wire cain_b,

output wire [7:0] sm_db

);

assign ad1_clk = sys_clk ;

assign sm_db={point1, ~sm_db_r };

wire [19:0] ch1_dec;

wire [11:0] ad_ch1 ;

wire ch1_sig ;

wire point1 ;

wire [6:0] sm_db_r ;

ad_9226 u1 (

.ad_clk (sys_clk),

.ad1_in (ad1_in ),

.ad_ch (ad_ch1 )

);

volt_cal u2(

.ad_clk (sys_clk),

.ad_ch1 (ad_ch1),

.ch1_dec (ch1_dec),

.ch1_sig (ch1_sig)

);

led_seg7 u3(

.clk (sys_clk),

.rst_n (sys_rst_n ),

.otr (otr) ,

.ch1_sig (ch1_sig ),

.ch1_dec (ch1_dec),

.sel (sel),

.point1 (point1),

.sm_db (sm_db_r)

);

range u4(

.clk (sys_clk),

.rst_n (sys_rst_n ),

.key (key_switch) ,

.led (led),

.scope ({cain_b,cain_a})

);

endmodule

19.4 Experiment Verification

Pin assignment

Signal Name	Port Description	Network Name	FPGA Pin
sys_clk	System clock	C10_50MCLK	U22
sys_rst_n	System reset	KEY1	M4
lg_en	ADG612 input	IO25	T15
hg_en	ADG612 input	IO24	U19
ad1_clk	Ad acquisition clock	IO28	V14
otr	Input voltage overrange flag	IO1	V24
sm_db[0]	Segment selection	SEG_PA	K26
sm_db[1]	Segment selection	SEG_PB	M20
sm_db[2]	Segment selection	SEG_PC	L20
sm_db[3]	Segment selection	SEG_PD	N21
sm_db[4]	Segment selection	SEG_PE	N22
sm_db[5]	Segment selection	SEG_PF	P21
sm_db[6]	Segment selection	SEG_PG	P23
sm_db[7]	Segment selection	SEG_DP	P24
sel[0]	Bit selection	SEG_3V3_D0	R16
sel[1]	Bit selection	SEG_3V3_D1	R17
sel[2]	Bit selection	SEG_3V3_D2	N18
sel[3]	Bit selection	SEG_3V3_D3	K25
sel[4]	Bit selection	SEG_3V3_D4	R25
sel[5]	Bit selection	SEG_3V3_D5	T24
ad1_in[0]	AD9226 acquisition data bus	IO0	U24
ad1_in[1]	AD9226 acquisition data bus	IO5	W23
ad1_in[2]	AD9226 acquisition data bus	IO4	V23
ad1_in[3]	AD9226 acquisition data bus	IO3	AA23
ad1_in[4]	AD9226 acquisition data bus	IO6	V22
ad1_in[5]	AD9226 acquisition data bus	IO2	AA22
ad1_in[6]	AD9226 acquisition data bus	IO7	V21
ad1_in[7]	AD9226 acquisition data bus	IO29	U14
ad1_in[8]	AD9226 acquisition data bus	IO30	V16

ad1_in[9]	AD9226 acquisition data bus	IO31	V17
ad1_in[10]	AD9226 acquisition data bus	IO27	U16
ad1_in[11]	AD9226 acquisition data bus	IO26	U15

Board verification

Use 1M sine wave as the signal source, AD9226 module to connect to GPIO1 and GPIO2 of 100T. Use the logic analyzer to capture the signal as shown in Figure 19.2.From the left to the right of the segment display, the first segment display is selected and lit to indicate that the input measurement voltage exceeds the AD9226 measurement range (the absolute value of VINA-VINB is less than or equal to the reference voltage, and the reference voltage of this module is 2V). The second segment display shows the sign of the input voltage (VINA-VINB). The last four digits are the input voltage value. When the input signal value is a slowly changing signal, the segment display can display the signal voltage amplitude.