reading data to hc164

[John_Smith]

HI
I have painted myself into a corner by offering to fit 3 bigger led displays to a friends machine that has 2 inch 7seg displays.
The displays I have are 7x5 alphanumeric unfortunatley driven by MAX7219..

The orig display has 3 x HC164 latchless shift registers, and I must leave this working, so I can tap into the data and clock feeds.

I bought home one of the displays and knocked up a test jig to send segment patterns with shiftout ( with no latch ) which works fine, but I have no idea what data rate is used in situ ( and I had to sell my scope )

#define data 18
#define clock 17
int delaytime = 500;


//  I got these patterns from the existing wiring between the chips and the 7seg led displays
byte zero  = B10001000;
byte one   = B11101011;
byte two   = B01001100;
byte three = B01001001;
byte four  = B00101011;
byte five  = B00011001;
byte six   = B00011000;
byte seven = B11001011;
byte eight = B00001000;
byte nine  = B00001001;


void setup()
{
  pinMode(clock, OUTPUT); // make the clock pin an output
  pinMode(data , OUTPUT); // make the data pin an output3
}
void loop()
{  //  shiftOut(data, clock, LSBFIRST, B01000000);
  shiftOut(data, clock, LSBFIRST, zero);
  delay(delaytime);


  // shiftOut(data, clock, LSBFIRST, B01000000);
  // shiftOut(data, clock, LSBFIRST, zero);
  //  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, one);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, two);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, three);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, four);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, five);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, six);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, seven);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, eight);
  delay(delaytime);
  shiftOut(data, clock, LSBFIRST, nine);
  delay(delaytime
       );
       }

I seem to be stuck just thinking about how to convert the 3 lots of serial bytes back into something I can use in a switch case routine to refer to my 5x7 matrix array patterns.

Its not a simple serial read, with its clock and data signals, and I cannot get shift(in) working.

Any suggestions ? I think my 73 years are catching up with me !

[wildbill]

Can you put the machine clock on an Arduino interrupt pin and use micros to tell you how fast it's running?

Maybe read the data line at the same time.

[John_Smith]

I think I will have to make a plan like that, it is at in a factory and I will have to balance my laptop on top of the machine ( and me )

Perhaps I can just have an interrupt on the falling clock pin to read the data, and save it in bunches of 8, or something.