12/22/2016 at 03:24 •
Here I combined screenshot from the datasheet with current prices (as available on DigiKey today):
As you can see not all combinations of packages/frequencies/cores are available (I used price for single chip and in case of availability of both commercial and industrial temperature ranges I wrote commercial price otherwise price of any available one).
Note: 33 MHz option is probably most problematic because of export regulations (too fast to ship outside of US?). Anyway it's obviously overkill in our case because according to datasheet for configuration with external program ROM the clock frequency of PIC17 should not exceed 25 MHz...
05/30/2016 at 01:37 •
I still have 3 green PIXPUTER boards from old batch, so I decided to make shortened version of PIXPUTER by removing WizNet, optocouplers, relays and wide extension bus on the right side:
This shortened version still has the processor (diamond shaped PLCC socket in the middle), ROM (large DIP on the left), PAL address decoder (smaller DIP at left-upper corner), RAM and other SOIC ICs, RTC (DIP on the right) and RS-232 chip and socket (on the top). 8+2 IO on the bottom of the board can be used to connect 2-line LCD-display as showed on older pics:
Also I want to connect little serial keyboard from Palm m100/m105 to it (people already connected this type of keyboards to DIY devices - it's called "Micro DataPad Mini Keyboard for Palm PDA" and it's still available on the Net here and there for about $10):
After that my PIXPUTER could be truly called "a computer" :)
05/25/2016 at 02:34 •
Package from China arrived yesterday :)
05/23/2016 at 22:58 •
It's strange, but I didn't know about other PIC17s until recently - along with PIC17C4X models there are bigger family PIC17C7XX (also obsolete):
with "monsterpic" PIC17C766 that has 66 IO-pins (ports from A to J)! Probably I'll try to build newer PIXPUTER around this one (with hope that all software from PIC17C4X will keep working). Another cool feature about them - ability to be programmed "In-Circuit" (but it's still one-timers that could not be re-programmed) and DigiKey even offers custom programming of PIC17C752 and PIC17C756A on order - in this case we can keep BIOS (and OS kernel) inside of the chip and all other software - outside (as pre-programmed into external 16-bit ROM or downloadable into external 16-bit RAM).
05/19/2016 at 03:23 •
As you probably know already I like to build computers from unusual things ;)
I wanted to design and build computer on PIC17 microcontroller since may be 2006 and when I found Circuit Cellar article from November 2000 about PIC17C44-computer with ROM, RAM and RS232 I finally decided to do that and WizNet contest became perfect opportunity for that. So along with ROM and RAM I added "smart" address decoder on PAL 16V8 programmable logic, RTC, optoisolated inputs, couple relays and Ethernet module WIZ810MJ (with W5100 chip on it with 4 hardwired sockets and 2x8KB memory buffers) to build I/O-board with remote control by HTTP from any browser. I didn't win the contest, but got "Distinctive Excellence" diploma and $100 from Circuit Cellar for the rights to use this board in the magazine (as I know my little article was never published, but still). WizNet brought this board to some exhibition in California and presented me a gift in form of 1GB USB flash-drive that broke a few months after that ;)
I still have 3 bare boards out of 4 manufactured in December 2007 (I paid $85 per board then):
But they have 2 errors (crystal instead of oscillator that is required for unprogrammed PIC17 and lack of reset circuit for W5100 as described in IO_Board.pdf), so in 2016 I finally re-ordered v1.1 of the board in China with fixed errors and colored in RED (now I paid only $18 per board):
On the right side you can see extension bus that could be used to connect other things as memory extension, game cartridge, videocard and floppy controller...
Schematics of v1.1 with fixed errors: