Step By Step: How To Build the N8VEM SBC

You can help by adding to this Wiki! These step by step instructions will be enhanced with more detail as more users complete their boards.

Step 1: Order a board. Please go to the N8VEM google group and check the thread regarding ordering of boards. If the thread has been inactive for a while and is not visible, please start a new thread. Boards are made in batches whenever enough orders come in. 

Step 2) Parts list. This step will be edited in the next 48 hours as of 3rd July. The parts list exists as a BOM in the files section but needs to be rewritten as something that could be submitted as an order to a supplier. Parts list and cost and suppliers for the Mini N8VEM is in the the folder Mini N8VEM Eagle Schematic and is similar to the standard N8VEM parts list. 

Step 3) Order an EPROM programmer. You will need to program eproms (or eeproms) to create a boot section of code that tells the CPU how to access disks to get CPM data. Larger EPROMs can also contain all the common and useful parts of the CPM operating system, so it is possible to have an entire operating system on a single chip. Go to www.ebay.com and search for Willem EPROM.

Step 4) Solder up the board. The board uses "old school" DIP chips which are easy to solder. Make sure there are no accidental solder bridges and that chips are inserted the correct way round (notch to the left).

Step 5) Burn the eprom. There are various eprom images around and some of the older ones have a bug with the xmodem program. A newer image is in the folders further down the right side of the wiki home page in Software and ROM images. In the mini N8VEM section is a series of files and programs that can create a new romimage from scratch with various different parameters. These include different baud rates (1200 to 38400), different sized eproms (32k or 1meg), and other options such as support for Terminate and Stay Resident programs (for keyboards and small LCD displays). You can build your own with a simple menu driven display, or put a request on the N8VEM forum with a list of files you would like included and ask for a custom image (free service, turnaround time of several days). 

Step 6) Build a link cable. If you have an old RS232 terminal with an old keyboard, this can be pressed into service. But a more practical solution is to use hyperterminal on a PC to emulate a terminal. You will need a RS232 cable and the easiest way to make one is to use D9 IDC plugs and sockets and several metres of ribbon cable (strip off 9 wires from a wider ribbon). [photo to add]. This brings out the serial from the back of a PC to the front which is much more practical. If your PC has no serial port, there are USB to serial adaptors on ebay.

Step 7) Copy some more CPM software to the board.You can use xmodem (on the eprom image in drive B) and hyperterminal or teraterm to send over files one at a time. Or you can include up to 1 meg of files on the eprom drive F (see step 5). Or you can get the vb.net program N8VEM from the mini N8VEM folder and use that as both a terminal and as a platform for making new romimages. Battery backup on the ram chip means the files stay on drive A even when the board is powered off.

Step 7a) Get some information about C/PM. For starters downlod this http://www.cpm.z80.de/manuals/cpm22-m.pdf This C/PM 2.2 manual gives an explanation about the commands. To expand your knowledge look also at the mainpage  http://www.cpm.z80.de/drilib.html for a great collection of scanned original C/PM docs.

Step 8) Enlarge the disk drive size to megabytes and gigabytes. There are active projects at the moment to build MMC SD flash ram adaptors, and Compact Flash adaptors, and IDE hard drive adaptors. These projects are not quite ready for publication but will be uploaded once the hardware and software is debugged. As of February 2009 the IDE iinterface is working. 

Step 9) Adding a small onboard display. There are 20x4 character LCD displays on ebay for very reasonable prices, and there are even larger displays available as well. Many CPM programs were designed to fit in an 80x25 character display which may be too large to be practical. However, simple basic programs that print "Hello" or "Enter n[1-10]:" will fit on these smaller displays.See the mini N8VEM folder for software. This uses some of the lines on the 8255 chip.

Step 10) Adding a keyboard.Software is available in the Mini N8VEM and uses 4 lines on the 8255 chip. You can use any PC keyboard with either a 5 pin DIN or 6 pin mini DIN connector. 

Step 11) Wireless routing. It is possible to sent RS232 signals over 500 metres using cheap wireless modules http://www.instructables.com/id/Build-a-500-metre-radio-data-link-for-under-40./  A work in progess is to interface these with the N8VEM board so it is possible to log into a board from a PC and control the board without a need for the board to have its own monitor or keyboard.

Step 12) Build a backplane, and add peripheral boards. More boards are being added to the N8VEM project.

Step 12a) Add a terminal using the Propeller chip and a vga monitor http://www.brielcomputers.com/files/pocketermrev1.jpg

Last updated 11th February by Dr_Acula