On Tue, 11 Mar 2008, Paul Lowe wrote: > Here's one way to do it (thought up by a Comp. E. student who thinks > he knows everything): > > Otherwise, here is a solution using only one data port in parallel: > > - Wire each 7 segment display to a digital 8 bit latch. > - Use one data port to send your seven bits of segment data to all > three seven segments via a bus > - Use two wires as multiplexing selection lines to select which seven > segment latch will receive the data. (e.g.: [00] -> segment 1, [01] > -> segment 2, [10] -> segment 3) > - Use some digital logic chips to check the multiplex selection lines > to see which digital latch to enable for loading. > > So: > > 7-bit Data line > (to all three displays)
I don't think that will work with this because it's 3 7 segment displays ganged in parallel. The latch idea would work for 3 separate 7 seg displays, however it's probably more sensible to refresh each one frequently (fewer parts needed). If the OP has something like this.. http://pdf1.alldatasheet.com/datasheet-pdf/view/168057/ETC/LDT-M514RI.html (although common cathode instead) Then they will need to update each separate display often enough so the user doesn't see any flicker (50Hz+). So you have 3 pins for 'select' (connecting to pins 12, 9, & 8), say PORTB[0:2] and 7 for the segments, say PORTC[0:7] (pins 1, 2, 3, 4, 5, 7, 10, 11). Make sure you have resistors in series with the LEDs or they will probably get fried :) DDRB = 0x07; DDRC = 0x7f; while {1} { PORTB = 0x06; PORTC = num2seg(hundreds) _delay_us(20); PORTB = 0x05; PORTC = num2seg(tens); _delay_us(20); PORTB = 0x03; PORTC = num2seg(ones); _delay_us(20); } (ie port B pulls low and port C pulls high - this presumes the AVR can sink & source enough current to drive your LED - should be OK I think) You can also put this into a timer routine with minimal work. If you aren't sure of the pinout I suggest carefully probing with a fairly high value resistor (5kOhm I guess) and check. I suspect that 99.9999% of all 7 seg displays have the same pinout as on that data sheet though. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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