Z80 Emulation Using the RP2040

[Chris Savage]

I had not realized that TASM works in Linux! TASM just went way up in my estimation.

LOL TASM just works. I have used it to assemble on at least 4 different platforms, including the Z80, 6502, 6809 and 8085, as well as variants of these.

[Chris Savage]

Gentlemen,

If I may ask (I have so many things going on at once), what was the consensus with regards to building a Z80 emulator? In the first post I mentioned a cheap hardware platform and some software. But our conversation evolved across two threads and I wanted to order some hardware this weekend for it.

What sounds like the best bang for the buck for build an emulator for those who want to assemble for Z80, without an actual Z80 IC?

[granz]

I still think that the Pico with RunCPM will be the best deal:

Amazon:

• SD Card Breakout (2 ea) - $5.49 - https://www.amazon.com/DIYables-Adapter-Arduino-ESP8266-Raspberry/dp/B0BXKLNN2L
• Raspberry Pi Pico H w/ USB Cable - $9.90 - https://www.amazon.com/Microcontroller-Development-Pre-Soldered-Dual-Core-Multi-Function/dp/B0DSBQS5ZF/
• 830 Point Breadboard - $4.59 - https://www.amazon.com/California-JOS-Breadboard-Solderless-Distribution/dp/B0BRQX6G3T/
• 1 GB Micro SD Card - $7.79 - https://www.amazon.com/Lerdisk-Wholesale-1GB-Produced-Authorized/dp/B0D3KWY34B
• Hookup Wire - $3.86 - https://www.amazon.com/MECCANIXITY-Breadboard-Electronics-Electronic-Projects/dp/B0F1YDQ53Q

Total - $31.63 + sales tax
No shipping fee for Prime Members.
Price could be considerably less for someone who can solder.
No soldering, nothing else to purchase.
RunCPM firmware is a single file that is extremely easy to install on the Pico - great for complete beginner.

[Chris Savage]

The first two links are identical. 

[granz]

Thank you for catching that, the link has been corrected. I also put in my description of that item that it includes the USB cable. That particular sale item also includes the three-pin male header for the Debug port, but for a total beginner they could simply ignore that.

If you like this, next payday (18 Feb) I will order this set, and do a write-up on how to put this kit together and set it up for RunCPM. It would be better if I put together an A: drive image specifically for this kit - the drive images that are recommended by the RunCPM project are WAY too much for a beginner. The image that I will set up will just have the assembler/linker, an editor (probably ZDE,) a simple language like BASIC, maybe a word processor (WordStar?) and maybe a game, or so.

The only thing that would be required beyond this set would be a computer/tablet/phone. I will give directions for setting up a Linux, a Windows, a Mac (I just need to set up one of my Mac Minis) computer and an Android tablet/phone. I would need someone else to add the instructions for an IOS I-Pad/I-Phone, as I don't have any of those.

How does this sound to you?

[Chris Savage]

The image that I will set up will just have the assembler/linker, an editor (probably ZDE,) a simple language like BASIC, maybe a word processor (WordStar?) and maybe a game, or so.

The only thing that would be required beyond this set would be a computer/tablet/phone. I will give directions for setting up a Linux, a Windows, a Mac (I just need to set up one of my Mac Minis) computer and an Android tablet/phone. I would need someone else to add the instructions for an IOS I-Pad/I-Phone, as I don't have any of those.

How does this sound to you?

Well, I do have a couple of questions. Why did you choose a 1GB SD card? I have noticed that on typical R-Pi boards, the included / recommended SD card size has steadily increased over time, though I have never taken note of the used space after an OS has been installed. Often, larger cards are cheaper. So unless a small card is necessary, it is often cheaper to go larger. I wasn't sure if there was a size limitation on the driver you're going to be using?

Also,

Right now I have all the parts you linked in my Amazon cart. With two of everything (except what I already have). My intention is to follow what you're doing on my end. I am going to send the items in the list to you after they arrive. I was the one asking about doing this and I do not have the time to experiment with this, therefore, I will provide the parts if you'll write up a tutorial on putting this together. Depending on the results, I may put it up on the main website as a project. But first I want to see how it works out with the specified parts.

I will delay placing the order until I hear back from you on the SD card size specifications.

[granz]

Well, I do have a couple of questions. Why did you choose a 1GB SD card? I have noticed that on typical R-Pi boards, the included / recommended SD card size has steadily increased over time, though I have never taken note of the used space after an OS has been installed. Often, larger cards are cheaper. So unless a small card is necessary, it is often cheaper to go larger. I wasn't sure if there was a size limitation on the driver you're going to be using?

I have had a pretty rough several days, and was exhausted. When you texted, I had already gone to bed. Starting to feel a bit better, and no appointments until Friday, so another few days of early-to-bed, late-to-rise  will, hopefully, get me better rested.

As I mentioned in the texting chat, I spec'ed the lowest price for everything. I also wanted a single source for everything - no multiple orders. Also, with Amazon, many people have the Prime membership, and shipping on all of that stuff is free for Prime. Plus, a whopping 1 GB of disk space is monstrously huge for a CP/M system. CP/M was meant for floppies, and when hard drives came out, only supported 5MB (max of 8 MB per drive.) Regular Pi systems need far more space than CP/M, however they are able to do way more - but you wanted a system for Z-80 assembly programming, and this hardware, along with some (free) CP/M software will do the job.

Now, that doesn't mean that this is the bottom-of-the-barrel pricing. Anyone who has fair-to-decent soldering skills can get cheaper by soldering the kit themselves, and lower prices can be found on places like AliExpress (if you are willing to risk it,) or stopping by their local MicroCenter, or other electronics store. And, most people who are interested in this project would probably have a breadboard, and jumper wires, etc. but, like I said the idea for these choices was to be easily available to the lowest common denominator in newbies, for the cheapest price.

Also,

Right now I have all the parts you linked in my Amazon cart. With two of everything (except what I already have). My intention is to follow what you're doing on my end. I am going to send the items in the list to you after they arrive. I was the one asking about doing this and I do not have the time to experiment with this, therefore, I will provide the parts if you'll write up a tutorial on putting this together. Depending on the results, I may put it up on the main website as a project. But first I want to see how it works out with the specified parts.

I will delay placing the order until I hear back from you on the SD card size specifications.

Well, I appreciate that; I can do that. Also, if you have Prime, it would be cheaper for you to make two orders, one shipped to you, and the other sipped to me. It would save you the cost of shipping from your place to mine. Plus, save the price of the box, and packing.

[granz]

By the way, if you do not have a Prime subscription, let me purchase these parts, and have one set shipped to you. I do have a Prime membership.

[Chris Savage]

I have had a pretty rough several days, and was exhausted. When you texted, I had already gone to bed. Starting to feel a bit better, and no appointments until Friday, so another few days of early-to-bed, late-to-rise  will, hopefully, get me better rested.

I can appreciate that. I am home from work today. Clearing snow two days in a row took a toll on me. My back and feet just can't do it. Recovering today, since it's not snowing.

As I mentioned in the texting chat, I spec'ed the lowest price for everything. I also wanted a single source for everything - no multiple orders. Also, with Amazon, many people have the Prime membership, and shipping on all of that stuff is free for Prime. Plus, a whopping 1 GB of disk space is monstrously huge for a CP/M system. CP/M was meant for floppies, and when hard drives came out, only supported 5MB (max of 8 MB per drive.) Regular Pi systems need far more space than CP/M, however they are able to do way more - but you wanted a system for Z-80 assembly programming, and this hardware, along with some (free) CP/M software will do the job.

I guess I was thinking about the overhead of the R-Pi OS, but that's fine. You're right. My sole interest in this is a cheap Z80 assembly platform.

Well, I appreciate that; I can do that. Also, if you have Prime, it would be cheaper for you to make two orders, one shipped to you, and the other sipped to me. It would save you the cost of shipping from your place to mine. Plus, save the price of the box, and packing.

Obviously, you're thinking better than I am. I didn't even think about that. I will place two orders right now and have one shipped to you.

[granz]

I guess I was thinking about the overhead of the R-Pi OS, but that's fine. You're right. My sole interest in this is a cheap Z80 assembly platform.

With the RunCPM firmware, that is the OS, not Raspberry Pi OS. RunCPM has a pretty small footprint (325 KB)! And, that is completely onboard the Pico - the entire SD card is for CP/M files.

Obviously, you're thinking better than I am. I didn't even think about that. I will place two orders right now and have one shipped to you.

Thanks, I'll get started on the write-up.

[Chris Savage]

With the RunCPM firmware, that is the OS, not Raspberry Pi OS. RunCPM has a pretty small footprint (325 KB)! And, that is completely onboard the Pico - the entire SD card is for CP/M files.

I ordered everything in the list for you. For me, I ordered the R-Pi, SD Card and SD Card Sockets. I have plenty of breadboards and wires.

As with the project that @Jeff_T is working on, once I complete things on my end, I may post the project in my own words to the main website, with attribution to you both as well as linking to your posts here in the Member Project section.

[Chris Savage]

As is the case pretty much every time with Amazon, my order, which was due today, is now late and expected tomorrow instead. 

[granz]

As is the case pretty much every time with Amazon, my order, which was due today, is now late and expected tomorrow instead. 

Unfortunately that is becoming the norm for Amazon. The other day, I was trying to set up one of my new Raspberry Pi systems as Spock, and realized that I needed a micro-HDMI to HDMI adapter. I selected the option to "get it by tomorrow" morning in the search parameters, and a set came up that looked good. However, when I actually tried to order the things, they were two-day (not the over night that I searched for.  ) I paid the additional money for overnight - by 11:00 in the morning. Of course, even with spending the extra shipping cost, it did not come until late yesterday. I cancelled the order, and got my money back - I did not like paying the extra, especially when it did not arrive by the time that they said it would!

I ended up using an older Pi 3 (has a full-sized HDMI port) for Spock, and we were able to watch a movie last night on Spock. So, I may just use that Pi 3 for Spock, and use the Pi 5 (with the micro-HDMI) for something else. So, I just placed a regular "Prime" order for some adapters, and will accept 2- to 3-day delivery, without the extra charge.

Amazon is getting worse, and worse. I wish that we had a MicroCenter (or better yet, a Fry's or something) close by.

[granz]

Well, I got everything except for the SD Card Breakouts - they should arrive on Monday.


I did get a bit of a start there, I received the SD Card, but it was a micro card - I thought that the breakout was full-sized. It only took a minute, or two, to find out that they were both for micro- and not full-sized.

The breadboard does come with some jumper wires, but they are all male-to-female jumper wires. I'm not sure how the female connectors would help with a breadboard, but they were there any way. Yet another annoyance for the beginner - we may want to choose another breadboard, one without the jumper wires that the buyer needs to just "throw out" (get rid of them.) That would just make the newbie wonder why he should waste his money.

Interestingly, there is no mention of jumper wires in the description on that Amazon page. I guess that they just added the wires as a bonus - makes it more difficult to choose these for a beginners kit, although great for non-beginners.

If you were to decide to sell these kits all in one pack, then you could save a huge amount of money by buying in bulk, and soldering things yourself. This is just for the newbie who is wanting to get into this assembly programming by him-(her-?)self.

[Chris Savage]

I did get a bit of a start there, I received the SD Card, but it was a micro card - I thought that the breakout was full-sized. It only took a minute, or two, to find out that they were both for micro- and not full-sized.

Yeah, almost nobody uses full-sized SD cards anymore. Just a fact of life, I guess.

The breadboard does come with some jumper wires, but they are all male-to-female jumper wires. I'm not sure how the female connectors would help with a breadboard, but they were there any way.

Here is where my own recent experience shines. The vast majority of sensors and accessories I get for the Arduino have pins on them. I use the M-F wires to connect these devices to the breadboard. You can see an example here: New Project

It's especially nice when the pins are such that you can't actually plug the board into the breadboard.

If you were to decide to sell these kits all in one pack, then you could save a huge amount of money by buying in bulk, and soldering things yourself. This is just for the newbie who is wanting to get into this assembly programming by him-(her-?)self.

Yeah, something to think about, especially since you've identified other uses for it than what my interests are.

P.S. - My last part came in, so now I have everything I need to realize your configuration.

P.P.S. - Two things about these card readers that I am mildly disappointed with is the PCB edges (rough) and the lack of a card detect pin. I know we're trying to keep costs down, but that's something I use in my own designs, usually.