DSD 7 segment LED sample rate display G. Forrest Cook 1993 Here's a circuit that will take signals from the DSD and convert them to 2 LED digits for displaying the sample rate and lock status. Credit goes to Bryan Levin for the original idea. This definitely falls under the category of creaping featurism for the DSD but it adds lights to the box so it's inherently cool. The numbers to display are: 00 for unlocked, 32 for 32Khz, 44 for 44.1Khz, and 48 for 48Khz. Some basics about LED displays: LED displays come in several varieties, common cathode(CC), common anode(CA), and multiplexed. This circuitry will work with CC and CA but not with multiplexed displays. In other words, use single digits, most multi-digit displays are multiplexed. In common cathode displays, the common pin is grounded. In common anode displays, the common pin is connected to +5 volts. All LED segments MUST have a current limiting resistor or they will smoke. Decimal points may be on the left or the right side depending on which type of display you use. If you go with the option for the .1 display, use the decimal point that's between digits 2 and 3. The segments in the displays are named as follows: Display1 Display2 (optional Display 3) -------- -------- -------- | A1 | | A2 | | A3 | |F1 B1| |F2 B2| |F3 B3| | G1 | | G2 | | G3 | |E1 C1| |E2 C2| |E3 C3| | D1 | | D2 | | D3 | -------- -------- -------- There are also DP1 and DP2 and DP3 "segments" for the decimal points. A little logic circuits type math: The signals the display circuitry needs from the DSD are FC0, FC1, (sample rates bits) and ERF (inverted lock). These are fed into the Eprom Address bits A0, A1, and A2 respectively. The following tables show all of the state information. Table 1 shows the individual segments and the states in which they are active. Several segments in Table 1 have the same active states so they may be combined as shown in Table 2. Table 2 also shows which EPROM Data pins the single segments and segment groups are assigned to. Note that 3 segments, B1,C1,B2 are always on so they do not need to be driven by the EPROM at all. Table 3 shows the EPROM programming information and lists the states. Table 1 Table 3 ------------------------ --A2--A1--A0----------------------------------------- |Segment|States when on| |ERF|FC1|FC0|Disp|State|D7|D6|D5|D4|D3|D2|D1|D0|DHEX| ------------------------ ----------------------------------------------------- | A1 | 2+3 | | 0 | 0 | 0 | 44 | 0 | 0| 0| 1| 0| 0| 1| 1| 0| 26 | | B1 | All | | 0 | 0 | 1 | 32 | 1 | 0| 0| 0| 1| 0| 1| 1| 0| 16 | | C1 | All | | 0 | 1 | 0 | 48 | 2 | 0| 0| 0| 1| 0| 1| 0| 1| 15 | | D1 | 2+3 | | 0 | 1 | 1 | 00 | 3 | 0| 0| 0| 1| 1| 0| 1| 1| 1B | | E1 | 3 | | 1 | 0 | 0 | 00 | 4 | 0| 0| 0| 1| 1| 0| 1| 1| 1B | | F1 | 0+1+3 | | 1 | 0 | 1 | 00 | 5 | 0| 0| 0| 1| 1| 0| 1| 1| 1B | | G1 | 0+1+2 | | 1 | 1 | 0 | 00 | 6 | 0| 0| 0| 1| 1| 0| 1| 1| 1B | | | | | 1 | 1 | 1 | 00 | 7 | 0| 0| 0| 1| 1| 0| 1| 1| 1B | | A2 | 1+2+3 | ----------------------------------------------------- | B2 | All | | C2 | 0+1+3 | | D2 | 1+2+3 | | E2 | 1+2+3 | | F2 | 0+1+3 | | G2 | 0+1+2 | | | | |(optional) | | DP2 | 0 | | B3 | 0 | | C3 | 0 | ------------------------ Table 2 -------------- |D#|Segments | -------------- |D0|A1,D1 | |D1|F1,C2,F2 | |D2|G1,G2 | |D3|E1 | |D4|A2,D2,E2 | |D5|B3,C3,DP2| (optional) |ON|B1,C1,B2 | -------------- And finally, the hardware: Here is the pinout of the 2716 EPROM, any old PROM may be substituted with appropriate pinout changes if you can burn the data into it. Note that this describes the circuitry to drive VERY SMALL LED displays, it is much better to add a driver chip to get more current for the LEDs. 2716 Name Connect to pin 1 A7 ground 2 A6 ground 3 A5 ground 4 A4 ground 5 A3 ground 6 A2 ERF From DSD, U1 pin 25 7 A1 FC1 From DSD, U3 pin 23 8 A0 FC0 From DSD, U3 pin 22 9 D0 Segments A1,D1 through 330 ohm resistors or driver IC 10 D1 Segments F1,C2,F2 through 330 ohm resistors or driver IC 11 D2 Segments G1,G2 through 330 ohm resistors or driver IC 12 A5 ground 13 D3 Segment E1 through a 330 ohm resistor or driver IC 14 D4 Segments A2,D2,E2 through 330 ohm resistors or driver IC 15 D5 optionally connected to DP2 and B3,C3 through 330 ohm resistor or driver IC. 16 D6 no connection 17 D7 no connection 18 CE ground 19 A10 ground 20 OE ground 21 VPP +5V 22 A9 ground 23 A8 ground 24 VCC +5V The B1,C1,B2 segments all connect to +5V through 330 ohm resistors. Actually, these resistors should be a higher value to equalize the brightness since the EPROM can't drive as much current as the +5V supply. Something around 560 ohms should work ok. I really recommend driving the LED with an additional driver IC, the display will be brighter and the EPROM will be cooler. I used a 74LS241 and a pair of common cathode displays. Note that the always on segments B1,C1,B2 are driven by the LS241 to equalize segment current. I included the option of using the EPROM D5 pin to drive a third digit to display the . and 1 in 44.1, if you don't care use the 3rd digit, D5 can be left unconnected. For common anode displays, I suggest using a common 74LS04 IC, it has 6 inverters and there are no enable pins to fuss with. LS241 Name Connect to 1 1G! ground 2 1A1 2716 pin 9, D0 3 2Y4 no connection 4 1A2 2716 pin 10, D1 5 2Y3 Segments B1,C1,B2 through 330 ohm resistors 6 1A3 2716 pin 11, D2 7 2Y2 Segments B3,C3,DP2 through 330 ohm resistors (optional) 8 1A4 2716 pin 13, D3 9 2Y1 Segments A2,D2,E2 through 330 ohm resistors 10 GND ground 11 2A1 2716 pin 14, D4 12 1Y4 Segment E1 through a 330 ohm resistor 13 2A2 2716 pin 15, D5 (optional) or ground 14 1Y3 Segments G1,G2 through 330 ohm resistors 15 2A3 +5V 16 1Y2 Segments F1,C2,F2 through 330 ohm resistors 17 2A4 ground 18 1Y1 Segments A1,D1 through 330 ohm resistors 19 2G +5V 20 VCC +5V Pinouts for various LED displays differ, I recommend using the data sheet first and failing that, a 5 volt power supply with a series 330 ohm resistor can be connected to the various pins on the display to find out which segments are connected to which pins. Some displays have 1 "common" pin and others have 2 "common" pins, truly uncommon. Parts Sources: JDR Microdevices has a good deal going on displays, the FND357 CC display is $1.09, the Man74 CC display is $0.99. They also stock a bunch of suitable TTL driver ICs and have no minimum order. Phone: 800-538-5000 For once, Digi-Key falls short, they do have displays but they are kind of pricey. Ratty-ole-shack probably sells appropriate displays, you could also hack some out of an old calculator or your VCR :-) ***** You may need a higher current power supply if ***** you use the 7 segment mod, assuming 5ma per segment X 12 segments ***** all on at once for "00", it will need 60ma plus chip current, I'd ***** recommend at least another 100ma of capacity, more if you run ***** your LEDs brighter. Battery operated folks should definitely have ***** a defeat switch on the + supply of this circuitry. Have fun hardware hacking.