read in the display on 2 cascaded seven segment displays.

[isabella]

HI ALL,

IM STRUGGLING WITH THIS PROJECT IM TAKING ON.

HERE GOES........

THERE IS 2 CASCADED 7 SEGMENT DISPLAYS WHICH DISPLAYS A 'TRIP CODE'. THIS CODE RANGES FROM 00 TO 99.
I WANT TO READ THAT CODE IN MY PIC PROGRAM. AFTER I KNOW WHAT NUMBER IS DISPLAYED, I HAVE TO MATCH IT WITH A DESCRIPTION FOR THAT SPECIFIC NUMBER. THIS DESCRIPTION WILL THEN BE DISPLAYED ON A LCD.

NOW....HOW DO I MANAGE TO DETECT WHICH NUMBER IS DISPLAYED?
THE INPUT TO THE SEVEN SEGMENT DISPLAYS ARE a, b, c, d, e, f, g, h, DM, DL

pleeeeeeeze HELP!!!!:-(

 

[anothermort]

Well it looks like you need to wire a-h to portb0-7 (so you can use a portb interupt on change)
Then hook up DM and DL to another two ports!
Set all of the above as inputs

When the 7 segments are lit the interupt will fire off.
Read all of the port values and use these to work out the trip number.
Might need a look up table in there.
Obviously this needs to be done twice for both digits

not sure how you will sync it so you dont end up with 10 when it was 01!
This would depend on the refresh rate of the seven segments

Good luck

 

[Kurenai_ryu]

Well it looks like you need to wire a-h to portb0-7 (so you can use a portb interupt on change)
Then hook up DM and DL to another two ports!
Set all of the above as inputs

When the 7 segments are lit the interupt will fire off.
Read all of the port values and use these to work out the trip number.
Might need a look up table in there.
Obviously this needs to be done twice for both digits

not sure how you will sync it so you dont end up with 10 when it was 01!
This would depend on the refresh rate of the seven segments

Good luck

i think you should sync with DM and DL
once the DM digit is readed, the DL should be readed... hopefully they aren't doing PWM so you only need to do this once at every change... (DM and DL are changing very fast)

once you got both digits, decode them (how? just read some data first and make a table.) and compare over time,
if its stable, just show your message on the LCD,


don't forget to check the voltages on ther led display,

 

[pavans2510]

from where is that trip code coming?

 

[isabella]

thank you all for replying. i want to program in C and im not sure how to implement your advise in C programming. the trip codes come from a card that i'm not allowed to alter. so i must use the inputs of the display panel.

 

[masterleous]

thank you all for replying. i want to program in C and im not sure how to implement your advise in C programming. the trip codes come from a card that i'm not allowed to alter. so i must use the inputs of the display panel.

In cascaded display module, each 7 Segments have to be display for atleast 100micro seconds to 5 ms, this time is different for different display, two segments may have 1ms to 10ms time range.

For detection, first take all 7 segments inputs to micro (including each segment's enable input to interrupt inputs).
Now, the main task will start to detect the number, when ever segment enable input comes to micro via interrupt. read 7 segments inouts and calculate that number, do the same for other interrupt input. From this way you will get your results.

 

[pavans2510]

**broken link removed**

check the above link it might help to reduce the use of number of i/o pins.

 

[isabella]

thank you for your replies.

can you help me with a sample code for the interrupt routines. in the routines i want to determine the decimal value of the msb input and then store it so i can add it to the value of the lsb. i have to use 2 external interrupt and i have no idea how. also im not sure what pic to use for the whole application. one with enough in and outputs. heres a drawing of how the current panel is connected, i have to work from that.View attachment untitled2.bmp

thanks again