Can any one help me with following code it is displaying only zero in the 7 segment leg even if i increasing Vin I have connected CS5550 SDI,SDO,SCK to 8051 port1 Thanks AD_VALUE_00 EQU 30H ; R:30H AD_VALUE_01 EQU 31H ; R:31H AD_VALUE_02 EQU 32H ; R:32H AD_DO BIT P1.0 ; CS5550UTPUT PORT AD_SK BIT P1.1 ; CS5550 CLOCK PORT AD_DI BIT P1.2 ; CS5550 INPUT PORT org 8000h ljmp main main: mov sp,#0dfh acall init_5550 adc_scan: acall ad_read mov ad_value_02,a mov 60h,a lcall 019bh acall ad_read mov ad_value_01,a mov 60h,a lcall 019bh acall ad_read mov ad_value_00,a mov 60h,a lcall 019bh ret ad_read: mov b,#08 read_next_bit: clr ad_sk nop mov c,ad_do rlc a setb ad_sk ;nop ;nop djnz b,read_next_bit ret init_5550: mov a,#04h ;write enable command acall ad_write ;gain PGA mov a,#00h acall ad_write mov a,#00h acall ad_write mov a,#00h acall ad_write ;gain mov a,#04h ;write enable command acall ad_write ;filter mov a,#00h acall ad_write mov a,#00h acall ad_write mov a,#20h ;High pass filter enable acall ad_write ; mov a,#74h ;write enable command acall ad_write ;conversion mov a,#80h acall ad_write mov a,#00h acall ad_write mov a,#00h acall ad_write mov a,#0e8h ;start conversion acall ad_write sjmp adc_scan ad_write: mov b,#08 write_next_bit: clr ad_sk rlc a mov ad_di,c setb ad_sk nop djnz b,write_next_bit ret end