PC Board artworks off to the fabricator

As I might have mentioned earlier, I was debating whether to focus on the FatFS library conversion or layout the PCB.  I was at the point that I needed the PCB to do any software development beyond the FatFS library conversion.  Well, after messing around with the FatFS conversion for a few days and knowing it needed a lot of work still, I caught a case of ADD and decided to switch to the PCB layout.  I THOUGHT I was ready to just go to layout BUT alas, upon looking at the schematic, I realized I still needed to finish it.  So be it ….  A few hours later and I was ready for layout.

I am glad I decided to go right to PCB rather than try to add parts to the solder-less breadboard … or worse, try to hand-wire a “one-off” using a perfboard.  Once the netlist was imported to the layout package, I saw there were 112 nets with 287 connections.  It is far more economical to layout a PCB and have it fabricated for the low cost, which definitely saved my time in wiring and possible re-wiring a “one-off” board.

z80computer_pcbv110-3d
3D view of Z80 Computer – from top

It took a few hours of multiple route and cleanup sessions as I realized that I forgot to add this or I no longer needed that.  Overall, the layout looks clean.  Since there are only six (6) electrical pins and two mounting pins, the Micro-SD memory card adapter is located on the bottom of the board so as to save space on the top.   It can be seen close to the edge at the lower-right in the 3D render.

s-l1600
DS3231 RTC daughter-board

At the last moment, I decided to add on a DS3231 RTC daughter-board.  The DS3231 is connected to the AVR’s I2C interface.  I deemed it a necessary addition as one of the goals is to be able to run CP/M, which supports date and time stamping of files.  The DS3231 has a built-in oscillator and is a one-chip RTC solution.  The daughter-board is nice because it has a build-in battery and a tall 5-pin header socket that fits nicely over the top of the LM7805 voltage regulator.   I ended up using two (2) SMD parts, an NC7P157 MUX and a si2305 P-MOSFET.  The NC7SP157 is used to select between the “SDout” pin of the SD memory card and the 74HC299.  The SDmem card’s output goes tri-state when de-selected but the 74HC299 output pin does not, hence the MUX is needed.  The si2305 is a low RdsON (50mΩ max), high current (5.8A) P-MOSFET device, which is being used as a power switch between USB power and an external power connection to the main VCC supply.  There are a lot of pins with 100 mil spacing on this PCB, which made it impossible to route 287 connections on a double-sided PCB (with power and ground) using my usual 12.5 mil signal and 25 mil power/ground traces.  Since the fabricator can deal with 6 mil traces, I ended going to 6 mil signal and 20 mil power/ground traces.  Copper pours for the ground plane are easy and I always use them, top and bottom.

For those interested, the fabricator I used is http://youpcb.com.  I chose them because the fabricator I have used in the past was twice as expensive as these folks.  Since the per-PCB charge is based on the order quantity and the panel size, it was actually more economical to order 10 pieces for a few dollars more rather than 5.  One thing I noticed is that on the order page, the copper density defaults to 0.5 oz, whereas all fabs I have worked with in the past use 1 oz copper density.  Be aware that 1 oz copper density can be selected without any additional charge.

_z80computer_pcbv110
Z80 Computer PCB – V1.10

I’ve attached the final schematic in PDF format here and a 1x printout of the PCB silkscreen, top and bottom clad here.  WORDPRESS does not allow uploading text files so the BOM and PL are shown below.

I suppose that until the PCB’s arrive in about 2 weeks, I’ll get back on the FatFS library conversion.  Although, the 8052SBC PCB’s should be arriving in about a week and hopefully, the ATMEL AT89S52’s I have on order as well.

For those of you interested in this project, I have ten (10) PCB’s on order but I will not use all of them.  I am considering making them available on TINDIE for a reasonable fee.

Parts List:

Z80 Single Board Computer - AVR Subsection Revised: Tuesday, November 08, 2016
Z80_COMPUTER_V100.DSN Revision: 1.0


Design Name: F:\PROJECTS\ACTIVE\Z80COMPUTER\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN

Cross Reference November 8,2016 3:25:57 Page1

Item Part Reference SchematicName Sheet Library
____________________________________________________________________________

1 1.2K R3 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
2 1.2K R4 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
3 1K R6 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
4 1M R2 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
5 1N4001 D4 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
6 1N4148 D3 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
7 10K R7 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
8 10K R8 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
9 10K R9 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
10 10K R10 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
11 10K R11 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
12 10K R12 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
13 10K R13 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
14 22V10 U5 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
15 74HC14 U1A /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\GATE.OLB 
16 74HC14 U1B /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\GATE.OLB 
17 74HC14 U1C /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\GATE.OLB 
18 74HC14 U1D /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\GATE.OLB 
19 74HC14 U1E /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\GATE.OLB 
20 74HC14 U1F /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\GATE.OLB 
21 74HC299 U6 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\SHIFTREGISTER.OLB 
22 100K R1 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
23 100K R5 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
24 100NF C1 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
25 100NF C2 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
26 100NF C4 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
27 100NF C5 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
28 100NF C6 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
29 100NF C7 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
30 100NF C8 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
31 100NF C9 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
32 100NF C10 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
33 100NF C11 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
34 100NF C12 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
35 100uF C3 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
36 7805 U3 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
37 8255 U10 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\MISC.OLB 
38 ATF16V8B U4 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
39 CON10B J5 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\CONNECTOR.OLB 
40 CON10B J7 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\CONNECTOR.OLB 
41 CON10B J8 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\CONNECTOR.OLB 
42 CONN JACK PWR J2 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\CONNECTOR.OLB 
43 GM76C256 U8 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\SRAM.OLB 
44 GM76C256 U9 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\SRAM.OLB 
45 HEADER 3X2 J3 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
46 I2C J6 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\CONNECTOR.OLB 
47 JTAG HEADER J1 /Z80/AVR 1 S:\CAD\ORCAD\CAPTURE_LIBRARY\KSV.OLB 
48 LED D1 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
49 LED D2 /Z80 2 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\DISCRETE.OLB 
50 MicroSDcard M2 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
51 NC7SP157 U2 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
52 RTC J4 /Z80/AVR 1 C:\CADENCE\SPB_16.3\TOOLS\CAPTURE\LIBRARY\CONNECTOR.OLB 
53 SW TACT-SPST-C SW1 /Z80/AVR 1 F:\PROJECTS\CAD\CAPTURE_LIBRARY\KSV.OLB 
54 TEENSY20PP M1 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
55 TEST POINT TP5 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
56 TEST POINT TP6 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
57 TEST POINT TP7 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
58 TEST POINT TP8 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
59 TEST POINT TP10 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
60 TEST POINT TP11 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
61 TEST POINT TP12 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
62 TEST POINT TP13 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
63 TEST POINT TP14 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
64 TEST POINT TP15 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
65 TEST POINT TP1 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
66 TEST POINT TP2 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
67 TEST POINT TP3 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
68 TEST POINT TP4 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN 
69 Z84C0020 U7 /Z80 2 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V100\Z80_COMPUTER-V100.DSN 
70 sI2305 Q1 /Z80/AVR 1 F:\PROJECTS\ACTIVE\Z80\SCHEMATICS\V110\Z80_COMPUTER-V110.DSN

Bill of Materials

Z80 Single Board Computer - AVR Subsection Revised: Tuesday, November 08, 2016
Z80_COMPUTER_V100.DSN Revision: 1.0

Bill Of Materials November 8,2016 3:26:02 Page1

Item Quantity Reference Part
______________________________________________

1 11 C1,C2,C4,C5,C6,C7,C8,C9, 100nf
 C10,C11,C12
2 1 C3 100uF
3 2 D1,D2 LED
4 1 D3 1N4148
5 1 D4 1N4001
6 1 J1 JTAG HEADER
7 1 J2 CONN JACK PWR
8 1 J3 HEADER 3X2
9 1 J4 RTC
10 3 J5,J7,J8 CON10B
11 1 J6 I2C
12 1 M1 TEENSY20PP
13 1 M2 MicroSDcard
14 1 Q1 sI2305
15 2 R1,R5 100K
16 1 R2 1M
17 2 R3,R4 1.2K
18 1 R6 1K
19 7 R7,R8,R9,R10,R11,R12,R13 10K
20 1 SW1 SW TACT-SPST-C
21 14 TP1,TP2,TP3,TP4,TP5,TP6, TEST POINT
      TP7,TP8,TP10,TP11,TP12,
      TP13,TP14,TP15
22 1 U1 74HC14
23 1 U2 NC7SP157
24 1 U3 7805
25 1 U4 ATF16V8B
26 1 U5 22V10
27 1 U6 74HC299
28 1 U7 Z84C0020
29 2 U8,U9 GM76C256
30 1 U10 8255
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