New HW - Z80 SBC Design

[Tom Szolyga]

Hi Guys,

This is a new design spin of an old system.  I have a number of RC2014 systems, but I wanted a small system I could carry around.  I wanted to boot and run CP/M from a CF Card.  Thus, I designed a new version of the classic Grant Searle CP/M board.  My design is small, less than 100mm x 100mm.  There is an on board crystal oscillator or the 74AC00 package can be replace by a 14 pin can oscillator.  The reset circuit will assert /RESET until power is stable or after the reset button is pressed.   The IDE interface can connect directly to a CF card adapter.

I used EasyEDA to design the board.  The design is open to the public, just search for "RC2014" or "Z80".   The schematic, PCB layout and gerber files are available.  You can clone the design and make your own version or have EasyEDA fab boards.  The EasyEDA cost is $0.20 per board for a quantity order of 10 boards.  

I am thinking Version D of the board should use a Z180.  

I welcome your thoughts and ideas.  

Tom

[Steve Cousins]

Really nice design Tom, well done.

I think there is one little thing you have forgotten.... there does not seem to be a '14 bus connector!

Seriously though, very nice project.

Is there any good reason you did not take one of the spare outputs of the 259 to A16 of the RAM chip to allow for software bank select of the RAM. Admittedly it would be a bit restricted, but you could page the ROM in and move a couple of bytes in or out of the second RAM bank pretty quick. Not sure how much use that would be in practice. But you just can't 'waste' 64k bytes of RAM on a retro system. You just can't!!

Steve

[Steve Cousins]

Forgot to ask, but does it have a name? 

Every homebrew should have a catchy little name that just rolls off the tongue, like RC2014.

[Stephen Kelly]

Hello Tom,

Nice project.

I have ordered the pcb from EasyEDA and will have a go at building one.

Thanks for sharing it.

Cheers,

Stephen

[Steve Cousins]

Question for Stephen

I looked at ordering from EasyEDA. All seemed to be going well. I got to the Ordering screen where it said "For your first time order, the shipping cost will be free!". 

However when I got to the checkout there was a significant shipping charge. Is that what you found? So how much did your have to pay in total? 

Any comments appreciated.

[Paul Bigwood]

Nice design Tom. I like the use of the CF Card adaptor. i bought one like that from China expecting to use it on my RC2014, but got the one form Dr Baker in the end.

My only comment is that I would have liked a Z80 PIO on board as well for interfacing other i/O devices.

Paul 

[Phillip Stevens]

My only comment is that I would have liked a Z80 PIO on board as well for interfacing other i/O devices.

If you’re interested in lots of I/O off a Z80 SBC, then try Tindie YAZ180, for 8255 I/O and 2x I2C, plus USB serial and ESP-01S serial.

100mm x 160mm. Four layer PCB. 

And many optional blinking hex LEDs. 

Cheers Phillip

--

Sent from a Mobile Device. Replies may appear terse.

[Stephen Kelly]

@ Steve Cousins

I have ordered a number of PCBs from EasyEDA over the past year or two, so I didn't qualify for free shipping.

I generally use the air mail option.  It usually turns up in about three weeks.

Cheers,

Stephen

[Chris Scullion]

I must be missing something.  I can't find this board in EasyEDA. I can find lots of z80 and rc2014 results, but I can't tell if this one is in the search results.  Can someone post a link? I'd like to get a board to try.

[Mark Bramwell]

If another REV is being considered, I would like to suggest some mounting holes in the corners.

[Tom Szolyga]

Hi Mark,

I agree.  I need to add mounting holes.  I was so delighted that the autoroute finished, I just clicked order without adding the holes.

Tom

[Tom Szolyga]

Thanks Steve!

I thought about an enable for the second 64K of RAM via A16, but paging out the entire RAM memory seemed hard to use.  The board is pretty full right now, so adding memory paging logic requires higher level of integration.  One idea is to combine the random logic into a 22V10.  It could provide the paging functionality as well.  However, not everyone can program a 22V10, so there is a trade off.

Tom

[Stephen Kelly]

@Chris Scullion

Try this: https://easyeda.com/peabody1929/CPM_Z80_Board_REV_B_copy-76313012f79945d3b8b9d3047368abf7

Cheers,

Stephen

[Chris Scullion]

Thanks. That link helped. Placed my order.

[Jim80686]

> I am thinking Version D of the board should use a Z180.  

Hi, Tom:

A Z180 is an excellent idea. It would allow you to dump the SIO and leave space for a PIO or a floppy controller or maybe an expansion connector.

   <*> Jim

[Richard Deane]

Does anyone have a BOM/XLS  for ordering components from Mouser etc?

The suggested Toshiba memory chip is hard to find, what about alternatives?

On Friday, 30 March 2018 20:55:52 UTC+1, Tom Szolyga wrote:

[Tom Szolyga]

The Hitachi 128K x 8 memory chip works as well.  On the schematic I have the Hitachi 628128 part shown.  I use either this part or the Toshiba part and the board works ok.

One note:  the decoupling capacitors, the 0.1uf parts, have leads on 0.1" centers.  When ordering them, be sure to get the right lead spacing.  I found 100 of them for $1.53 on ebay: https://www.ebay.com/itm/100pcs-Multilayer-ceramic-capacitor-100nF-0-1uF-104m-50V-P-2-54mm-B104m-/291536405891 

Finally, you can extract a BOM on the EasyEDA website.  In the Schematic editor, there is a tab labeled BOM.  It will export a BOM for the project.

Tom

[Richard Deane]

thanks

[Richard Deane]

Tom,

Where can I find a CF card image for the CP/M build for this board?

I have a card on order and wish to get the free bits in order before I order components for a build/

Richard

On Saturday, 7 April 2018 19:34:06 UTC+1, Tom Szolyga wrote:

[Tom Szolyga]

Hi Richard,

The design is an updated version of Grant Searle's "CP/M on a breadboard".  All of the CP/M files are available on his website:

URL: http://searle.hostei.com/grant/cpm/index.html 

In addition, there are instructions about how to bring up the system.  This is the resource I used to bring up my system.

Tom

[Richard Deane]

Thanks
Thought there might have been some software tweaks for your board.

[Richard Deane]

In the UK the only distributor for a one-off Z80 SIO/2 with low delivery cost is RS Components, but they only have the 6MHz part (Z84C4206PEG) - can this be used instead of the 8MHz part, but with the existing specced crystal and 8MHz Z80 CPU?

Richard

On Saturday, 7 April 2018 19:34:06 UTC+1, Tom Szolyga wrote:

[Steve Cousins]

I remember seeing several different claims that you overclock Z80 family chips quite a bit without problems and don't recall any comments of this not working. So urban legend says yes.

[Richard Deane]

Do you have any part numbers for the SPDT right angle toggle switch (Power)? I need to get one the correct size, some are much smaller.

Cheers

Richard

[Richard Deane]

Thanks, I may give it a go, good to know it should work - though maybe I'll find I missed a few components or got some wrong, enough to justify another order with Mouser (free delivery for about £30 of order).

I got my circuit boards come through for Tom's design - 2$ + reasonable shipping charge - good price and not caught by Royal Mail £8 surcharge if imports aren't declared properly ( I have a few spare boards if anyone in UK wants one)  . Ordered most components from Mouser but forgot that I didn't have the Z80 SIO/2, I am using some ICs from a failed Zeta2 build, and forgot that uses a different chip.

Richard

[Steve Cousins]

Hi Richard

I'd really like to build Tom's SBC, so it would be good to acquire one of your spare boards.

Steve

[Richard Deane]

email me with your postal address (I think mine shows on the forum) and I'll whizz one into the post (from North Scotland, but post is pretty good). 

Richard

[Steve Cousins]

I have a PCB from Richard for Tom's SBC. Thanks Richard.

I built it and it works. 

It is a really nice little board. Good job Tom.

I have done a rough and ready port of my Monitor ROM and it seems to be working pretty well. See screen shot below.

I plan to include support for Tom's SBC in the next full release of the Monitor ROM.

I didn't have the reset chip, so currently only have a switch and pull-up. It seems to have a very unreliable reset at the moment, so I may have a problem to resolve.

Had to pinch the SIO from one of my RC2014 serial boards. Must order some more components.

Also my collection of switches did not include one to match the PCB's power switch holes. Its a pretty big switch for such a small board.

Initially I had a problem with the serial port not working. I found the cause was Tom's board has a different FTDI style connector pin-out to the RC2014. The Tx and Rx are the same but the handshaking lines are swapped. I made a little cross over board and now it works ok.

One thing concerns me a little about the board and that is the lack of current limit resistors on the serial signals. If powered from the FTDI board it is ok, but if you have a separate supply you need to think about what you are doing. Perhaps in practice nothing will get damaged if one side is not powered when the other is.

When trying to get my Monitor ROM to run, the first thing I missed was the digital I/O board the Monitor uses to display the results of its self test. Tom clearly chose not to make the board expandable, but I sure do miss it. I guess something had to go to fit on such a small PCB.

In conclusion I'd like to thank Tom for the design and Richard for the PCB, and to say again what a neat little SBC it is.

Steve

[Steve Cousins]

Tom, there is one part of your SBC that made me go "wow" when the Eureka moment hit me.

I have been writing a bit of code to select a paged ROM bank. Initially I thought having the two different ROM address lines on different port addresses would create quite a software overhead.

Indeed I started to write it with the usual test and jump logic, but then it occurred to me the genius of your design.

I've not actually tested this code, but to select a ROM bank specified in the A register with a value of 0 to 3, it appears the required code is just this:

OUT  (0x3F),A   ;Set ROM's A14 to bank bit 0

RRCA            ;Rotate bank bit 1 to bit 0

OUT  (0x3E),A   ;Set ROM's A15 to bank bit 0

You can even add a simple rotate A left to restore A's original value if required. 

I do like it when code ends up really short, efficient and simple.

So nicely done Tom.

My little homebrew, the "SC101", has ROM paging via a 74x259 similar to yours, but I thought it would be more efficient to use A0 as the data input. Wrong! However, at the time I was thinking about the efficiency of swapping between two 64k RAM banks. The use of A0 for the data input to the 74x259 means I can swap RAM banks with just a simple OUT (n),A where the value of A does not matter, as it is the value of 'n' that determines the RAM bank. Also this instruction does not change any registers or flags, which I figured would make it possible to swap RAM banks very quickly at the start of system calls and interrupts, thus reducing the overheads of having the operating system in a different RAM bank to the application.

Steve

[Tom Szolyga]

Thank you Steve for the complement!  Much appreciated.

Tom

[Stephan van Radecke]

@Tom: Can you please provide us with a part number for the toggle switch?

Thanks

Stephan

[Tom Szolyga]

Hi Stephan,

Here is documentation for the toggle switch and reset chip I used.

Switch:  

• Mfr: E-Switch
• Mfr part number 100SP1T1B4M6RE
  
• Digi-Key part number: EG2356-ND

Reset Chip:

• Dallas Semiconductor DS1233 Econo Reset
• Mfr part number:  DS1233-5+
• Digi-Key part number: DS1233-5+-ND

I have found both of these parts (or the equivalent of the switch) from other sources on the net through Google or eBay.  I like the switch, even though it is large, because it has 5 solder points to keep in on the board.  I tried a smaller, slide switch which broke off after some usage.

Best regards,

Tom

[Richard Deane]

Mouser switch 633-M2012S2A2W30 (NKK brand) has the correct pinning, soldered into my board but not been able to test it yet. (costs £2.60)

Richard

[Stephan van Radecke]

great, thanks a lot. (both)

I like those switches, too.

Stephan

[Thomas Riesen]

Tom,

Absolutely great, thank you for your effort!

I am a little bit confused about your picture of the assembled pcb, there are both, the crystal and the oscillator mounted. Why?

Thomas

[Thomas Riesen]

... sorry, one more question about the clock:

Grant used a 7.3728MHz crystal, in your schematic is a 3.6864 MHz listed ....   why?

I assume for the 74x04 works also a 74HCT04 and for all other TTL are 74LS types sufficient, right?

Thomas 

[Steve Cousins]

Hi Thomas

I've built Tom's SBC. It works well.

I fitted a 7.3728MHz oscillator to mine for software compatibility. Not sure why the schematic shows 3MHz.

I fitted an oscillator module so did not try the 74x04. I fitted HCT chips everywhere else.

If you build one, check the serial port handshaking lines carefully as they are not wired the same way round as the RC. I made a little adaptor board to swap the handshaking lines over. Also there are no current limit resistors on the serial lines, but I've not damaged mine yet.

Finally, one of the LEDs is shown reversed on the schematic.

Steve

[Thomas Riesen]

Hi Steve

I ordered the pcb today, so, I have now to wait for the delivery.

In the meantime I try to get the Small Computer Monitor 1.0 on my two years old Grant Searle circuit,

(see pic) but it doesn't work. Is there a major change on the board from Tom? I didn't saw such a big

change ...

Thomas

[Steve Cousins]

Hi Thomas

I've not checked Grant's design carefully, but I would have thought the version for Tom's SBC should work on Grant's design..

One thing that can stop the Monitor running on Tom's board is the CTS inputs on the serial ports. If either of these is left floating it can upset my Monitor's initialisation.

I could fix this in software as the hanging at reset is just my SIO test code being a bit too enthusiastic, although unused CTS inputs will still need grounding to satisfy handshaking requirements.

This is what I did on Tom's board (picture below). Hm, just noticed all the dust on the board!

Grant's schematic has a note by the CTS input saying "Ground if not being used".

Check carefully the connections for the TTL serial port as Grant's pin-out is different to the RC2014 and also different to Tom's SBC.

Other than that I can't think of any issues.

Steve

[Tom Szolyga]

It is possible to use either a crystal or a oscillator on the board.  I soldered in the crystal to test both options.  To use the crystal, load position U6 with a 74AC00 or 74HC00 (or 74HCT00 but I have not tried HCT).  To use the oscillator, load position U6 with the oscillator.  It turns out that a 14 pin oscillator has its output on pin 8.  The output gate for the 74xx00 uses the same pin.  This makes it possible to use either option by just changing U6.

I used a 3.6864 MHz frequency because I use worst case design rules.  The Z80A family is rated at 4MHz over voltage and temperature.  Running the system at or below 4MHz guarantees it will boot and run, regardless.

Finally, I use 74ALS logic because it is characterized over voltage and temperature.  Again, I am being conservative.  Other families will work fine at "typical" conditions: 5V and
room temperature.  Stay away from the original 7400 family of logic; it is terribly slow.

Best regards,

Tom

P.S.  My EE career started with a project designing minicomputers that just worked, no questions asked.  That "worst case" design philosophy (voltage, temperature and just adding up max prop delays) has stayed with me.

[Thomas Riesen]

Hi Steve, Tom

Thank you for your help!

On my Grant Searle system the CTS/Handshaking works well when I transfer programs via

the Download program. As you can see, I use a MAX232 and at the end is a RS232 signal

connected to the COM1: port of my PC.

@Tom:

Your SCM 1.0 is really great, I hope to get this running on my system.  

I am a little bit confused about the clock speed, is there really no change necessary when

my crystal is a 7.3728MHz type? Steve use also this frequency.

On my Grant Searle system I use a 74HCT00 type and it works well. I checked the signal

by a oscilloscope, the signal is proper and stable.

Thomas

[Tashima Hob]

Hi Tom and Hi guys, I have a question about the C10 component of the schematic. 

Comparing the layout and the photo of your built board, I have a doubt about the 50u capacitor, could someone kindly post a link of this component on Farnell/Digikey/Mouser/Rsonline/Ebay or any other shop you used? Or the component number? 

I don't want to make a mistake, I see the position is near the cpu. 

Thanks in advance and congrats for this amazing board 

[Steve Cousins]

Hi Tashima

I believe the label on the schematic is a typo. I'm sure it is a decoupling capacitor the same as C9, C11, etc. That's what I fitted and I'm sure it is correct.

Also watch out for LED2 which is drawn backwards on the schematic.

Also worth noting the serial header pin out is not the same as the RC2014.

Steve

[Tashima Hob]

Thank you indeed Steve, for your clear and quick answer

[Tom Szolyga]

Hi Steve and Tashima,

You are right about the capacitor.  I made a typo on the schematic when I placed C10.  It should be a 0.1 decoupling capacitor like the others.  I have corrected the schematic on EasyEDA. 

Best regards,

Tom

[John Newcombe]

Hi Tom, I have just built this machine, actually I built two. They both work really well so thought I would post a short review etc. 

Many thanks for your efforts.

https://glasstty.com/wiki/index.php/Grant_Serle%27s_Z80_SBC_using_Tom_Szolyga%27s_SBC-Z80_Board

Kind Regards
John

On Friday, 30 March 2018 20:55:52 UTC+1, Tom Szolyga wrote:

Hi Guys,

This is a new design spin of an old system...

  

    ...I welcome your thoughts and ideas.  

Tom

[Bill Knighton]

I’ve just finished this as my first Z80 machine and it’s
excellent. It’s hard to believe how nice turbo pascal
is on this.  
   My rs-232 to ttl board only has tx and rx.  I have both cts
pulled down with 10k resistors.  In the bios I can paste
code without issues but from cpm there are many errors
and I have to resort to adding a character delay in teraterm.
But even a delay of 1 destroys the speed.  Like 15 minutes
to paste kerm411.  If I found a rd-232 to ttl board with
handshaking would it clean this up?
  
   I also had a problem with installing cpm from the small computer monitor bios.  It would boot but hang on A>.
  It installed fine from Grant Searle’s bios so I switched back
to the small computer monitor bios after I installed cpm and
it all works.  

[Richard Deane]

I had the same problem of booting to cpm hanging at A》 prompt when using grant Searle cpm but was able to switch to the linc80 version of cpm and booting from scm.I am having problems with serial xmodem support. I shall try again using all Grant Searle components and see if I can boot into cpm ok and use xmodem.
Richard

[Richard Deane]

Can someone post a good bootable cp/m cf image containing a working xmodem to assist with debugging? If image is zipped it shouldn't be too large.
Richard

[Phillip Stevens]

Here in the RC2014 repository is a cpm drive zipped which contains XMODEM.
https://github.com/RC2014Z80/RC2014/blob/master/ROMs/CPM-IDE/CPM%20Drives/SYS.CPM.zip

As well as a bunch of other drives with cpm applications.

Cheers , Phillip

[Richard Deane]

Thanks,

Is that only for rc2014 as I am looking for one known to work on Tom's SBC? I thought it wasn't 100% compatible with rc2014. I know Tom's  SBC is a little off-thread for this rc2014 group, but it seems to have crept in as it has no better home (and where better to find active cp/m, rom and z80 fans?)

Richard

[Phillip Stevens]

This system disk works across a range (or all CP/M 2.2) systems, afaik.

Most of the utilities originated in from RunCPM, but I added some (including XMODEM) specific for RC2014.

The file SYS.CPM contains all the standard CP/M utilities, including the XMODEM optimised for the RC2014.

It is the system disk I use daily with CPM-IDE.

Depending on how you want to build your system, the boot code, BIOS, and CCP/BDOS need to be located appropriately either in ROM or on some boot tracks.

This file doesn't contain the CCP/BDOS & BIOS code at all. It is just a "system disk". But it does contain the working XMODEM for RC2014 that you asked for.

Regards, Phillip

 Richard Deane wrote:

Thanks,

Is that only for rc2014 as I am looking for one known to work on Tom's SBC?

[Richard Deane]

Thanks, I will try that as I do have a lot of different xmodem versions, and maybe I am using the wrong one.

I am hoping someone can post a known bootable cf image from Tom's SBC so that I know I have the correct system track structure and gets round any errors I have from the virgin build process.
Richard

[Bill Knighton]

I tried a z80 cpm/2.2 xmodem utility from github today. It works blazing fast on small files but stalls at 121 packets every
time. Kerm411 is having the same issues as is pasting
into download.com. Is there a file size limit? By any method
either with a 3.x crystal or 7.x crystal(57 or 115 kbaud) I am
having this problem using either the Grant Searle bios or the
Small Computer Monitor bios.
Maybe it’s my cp/m?

[paul]

This probably your BIOS overflowing the disc buffers and not having an interrupt routine to pause the data flow whilst the buffers are flushed to disc

I'd check what happens when the buffer overflows on your BIOS.

Paul

Sent from Samsung tablet.

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[Marco Maccaferri]

Il 14/04/19 22:41, Bill Knighton ha scritto:

Have you tested the ram chips ? Had a similar problem in the past and
turned out it was a faulty ram chip.

Best regards,
Marco.

[Bill Knighton]

It could be the ram. I used a UM61512. The only pin difference is A16 is an NC.

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[John Newcombe]

I used Minicom with a tx char delay of 1ms for 7.4Mhz and 2ms for 3.7Mhz and it all worked well. I have added details and some application package files at the article at the link I posted above. I do use CTS/RTS but with that turned off in Minicom it still works OK. On the second machine I use a cheap FTDI adapter and plug that straight into a USB port, this gives me CTS/RTS  and is quite a neat option.

I can create my image of my 128Mb Lexar CF card and pop it up there if it helps.

John

[Richard Deane]

I certainly would find it useful for debugging purposes to be able to access a pre-configured CF image for the SBC.  Thanks

Richard

[Karl A. Brokstad]

I have made two CF images which you can download from my site. I cant guarantee they work with sbc. LiNC.no has also one image available. 

Karl

Sent from my iPad

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[Richard Deane]

Thanks, I will try and then see if the sbc symptoms vary.

[MyklHn]

Karlab,

You've mentioned your web site a couple of times, but I don't know the URL.  Would you mind posting it?

Thanks,

Michael

On Friday, March 30, 2018 at 3:55:52 PM UTC-4, Tom Szolyga wrote:

Hi Guys,

This is a new design spin of an old system.  I have a number of RC2014 systems, but I wanted a small system I could carry around.  I wanted to boot and run CP/M from a CF Card.  Thus, I designed a new version of the classic Grant Searle CP/M board.  My design is small, less than 100mm x 100mm.  There is an on board crystal oscillator or the 74AC00 package can be replace by a 14 pin can oscillator.  The reset circuit will assert /RESET until power is stable or after the reset button is pressed.   The IDE interface can connect directly to a CF card adapter.

I used EasyEDA to design the board.  The design is open to the public, just search for "RC2014" or "Z80".   The schematic, PCB layout and gerber files are available.  You can clone the design and make your own version or have EasyEDA fab boards.  The EasyEDA cost is $0.20 per board for a quantity order of 10 boards.  

I am thinking Version D of the board should use a Z180.  

[Steve Cousins]

Karl's website is https://www.z80.no/

[Bill Knighton]

I can’t get anything good to happen with the new serial driver board. I put a logic analyzer on the RTS-CTS connection but it just stays high. Over several seconds and various serial commands including a download that’s over-running the Z80 board, that signal never moves. Shouldn’t I see a lot of activity?
Maybe even a blimp for each character?

[Bill Knighton]

I wrote a python script that meters the serial data. A Package
file now transmits at 0.0005 seconds between
Each character and an additional delay between each
“A: Download” command in the package. I left it at a second
and didn’t fine tune it. The 0.0005 character delay is tuned as
fast as I can reliable get it.
It’s visual studio python. I was too annoyed at Idle.

[Bill Shen]

Were you successful in getting XMODEM to load file?  It is much faster.  I have never used download.com, I used XMODEM exclusively to transfer CP/M files to a new CF disk.  The CP/M files are compressed with arj.exe on PC and decompressed with unarj.com on Z80 so file transfer is fast.  It takes me about 2 minutes to transfer CP/M2 to a new CF disk.
  Bill

[Mark Bramwell]

I have some notes on how to put xmodem on a freshly formatted CF card.

Seems to work well for me.  http://web1.foxhollow.ca/cpm/

download the xmodem.zip and read the .txt file.

Specifically:

-----------------------------------------------------------------------------------------
RC2014: How to load on a newly formatted CF Card
-----------------------------------------------------------------------------------------
Step 1: power on the RC2014 and hit space bar
Step 2: Paste XMODEM.HEX (a relocated XMODEM.HEX) to terminal window.
        This will load xmodem.com into high memory. This normally
        resides at 0100, but as the ROM is active, this area is not available.
Step 3: Type GFFE8 and press ENTER (this will relocate RAM 4100-->0100 and restart CP/M)
Step 4: When in CP/M, SAVE 17 XMODEM.COM

[Bill Knighton]

I was only able to get xmodem to work on small files. When they hit 122 packets it always failed. It was an xmodem on github and the author said it had a problem large files.
I’ve tried so many things over the last week that I can’t remember exactly what I did but I believe with xmodem
I also had to add a character delay in teraterm and even
1ms destroys the speed. Like 100 bytes/sec. It is disproportionate. With the python script to throttle the transmission I was able send 1.5-2 k byte/sec.
The post after this has links to a different xmodem and I will
Try it out next.

[Bill Knighton]

I’m going to try those instructions and that looks like a good link with some utilities I was looking all over for.

[Mikhail]

I made a board for the project in EasyEDA, but JLC ​​PCB did it very carelessly - there were many short circuits between conductors. From the boards I received, I found one without closures and assembled it. On the serial connectors between CTS and GND, I soldered SMD resistors 4.7 kΩ in size 0603.

But I didn't like how EasyEDA spread the board. I overdone it with the parameters:
track width - 12 mils
cleanliness - 12 mil
Chopper Aria Manager - cleanliness - 24 mil.
I replaced the big toggle switch with a small switch (you can put a small toggle switch instead), changed the wiring of the serial connectors to the corresponding RC2014 and installed a direct IDE connector. It turned out compact, very convenient board.
Instead of the CF module, you can use the DOM module. It is short and very comfortable.