Hi everybody I need a test jig that outputs three logic signals and has one logic input. Time resolution accuracy is ~500ns. It is needed to burn-in test a board (few at a time). We do not want to tie up CPU board that usually does this job. Probably something that has USB connector, may be set up to run by itself (so we do not have to have a PC attached to each of them) I have a feeling that somebody should make a plastic box that would do the job. Has anybody came across something like this? Thank you! Michael
It is very basic, I need a logic level to turn a power supply on, wait for few milliseconds when "ready" signal arrives, turn power supply off, generate ~1us pulse within at the same time (within few hundred ns), generate another ~2-5us pulse few hundred microseconds later. Repeat. Thing like this (just came across it)
would probably do the job. I'd like to find the one that:
Can you trigger your sequence with the ready signal with this device without the USB connection?
You could use a PIC for it. The free MPLAB IDE has a GUI and the serial connection of a PIC Start Plus can be connected with a USB-to-serial-converter :-) E.g. with the 16F628 the first pulse can be generated within a few hundred ns after the ready signal was received. Your description is not very exact, but I assume the following:
power on output = 1
wait for rising edge on the READY input
power on output = 0
generate 1us pulse on pulse output
generate 2us pulse on pulse output
The following program implements it, when clocked with 12MHz. If you don't need < 1us response time, you could use a cheaper PIC with a 4MHz external oscillator (you have to remove some NOPs and adjust the delay loop lower clocks)
; destinations W EQU D'0' F EQU D'1'
; port A bits READY EQU D'2' POWER EQU D'0' PULSE EQU D'1'
; init clrf STATUS clrf INTCON bcf STATUS, RP0 ; select bank 0 movlw D'0' ; set levels low movwf PORTA ; for port A movlw 0x07 ; turn comparators off and movwf CMCON ; enable pins for I/O functions bsf STATUS, RP0 ; select bank 1 movlw B'11111100' ; set bit 0 and 1 port A as output movwf TRISA - H'80' bcf STATUS, RP0 ; select bank 0
; power on POWER_ON bsf PORTA, POWER
; wait for ready signal low WAIT_READY1 btfsc PORTA, READY ; skip if ready signal is not set goto WAIT_READY1 ; else goto wait
; wait for ready signal high WAIT_READY2 btfss PORTA, READY ; skip if ready signal is set goto WAIT_READY2 ; else goto wait