This project was inspired by Habi and his work on getting a colour video output from the original PCW machines.
The only issue with his approach was that he used FPGA which i dont have and dont really want to spend the money on...
Anyway, what you will need to get this to work:
- Raspberry Pi Pico microcontroller board (any model, costs as little as £5)
- 4 resistors (1K, 100 and 2x270 Ohms)
This is how it all connects:
pico.png
NSYNC, VIDEO and GND inputs come from your PCW (either from the expansion port or from the Video connector on the system board). You can also get the 5V from PCW itself.
Outputs go to your RGB monitor (I use a SCART cable breakout). The resistor values don't have to be exact to make it work...it should also work with 220 or 330 Ohms, only the intensity of the colours will vary. In this implementation I am using a CGA 4 colour palette Black/Red/Greed/Yellow hence there is no need for RGB Blue output. Personally i cant stand the Cyan/Magenta CGA palette, hence i went for the Red/Greed one, but it shouldn't be difficult to adapt it to it.
Some photos of it in action on my old Technika TV, connected via SCART:
Screenshot 2025-01-02 145150.png
Screenshot 2025-01-02 145218.png
Screenshot 2025-01-02 145125.png
Screenshot 2025-01-02 140303.png
I also added an option to switch back and forth between 4 colour and standard green on black mode with a press of the button on Pi Pico.
It does look very nice and bright, for such a chip and easy solution.
The software side on the Pi Pico is just few lines of Micropython as below (heavily relying on the outstanding PIO feature of Pi Pico):
import rp2
from machine import Pin,freq
import time
@rp2.asm_pio(out_shiftdir=1,out_init=(rp2.PIO.OUT_LOW, rp2.PIO.OUT_LOW,rp2.PIO.OUT_LOW,rp2.PIO.IN_LOW,rp2.PIO.IN_LOW))
def video4colour():
wrap_target()
wait(1,gpio,20) # wait for end of Sync pulse
label("loop")
out(pins,3).delay(10) # output red,green and Sync to the monitor
in_(pins,2).delay(15) # sample 1st bit and Sync pulse then wait for 2nd pixel
in_(pins,1) # sample 2nd bit
mov(osr,isr).delay(2)
jmp(pin, "loop") # jump back to Loop if still in active drawing area
mov(osr,x)
out(pins,3) # output all zeroes to the monitor as we are in the blanking area
wrap()
@rp2.asm_pio(out_shiftdir=1,out_init=(rp2.PIO.OUT_LOW,rp2.PIO.OUT_LOW,rp2.PIO.IN_LOW,rp2.PIO.IN_LOW))
def video2colour():
wrap_target()
wait(1,gpio,20) # wait for end of Sync pulse
label("loop")
in_(pins,2) # sample video and Sync pulse
mov(osr,isr)
out(pins,2) # output video and Sync to the monitor
jmp(pin, "loop") # jump back to Loop if still in active drawing area
mov(osr,x)
out(pins,2) # output all zeroes to the monitor as we are in the blanking area
wrap()
freq(256000000)
colourSM = rp2.StateMachine(6, video4colour, freq=256000000,in_base=Pin(19),out_base=Pin(16),jmp_pin=Pin(20))
monoSM = rp2.StateMachine(5, video2colour, freq=128000000,in_base=Pin(19),out_base=Pin(17),jmp_pin=Pin(20))
monoSM.active(1) # start the 2 colour video initially
while True:
if rp2.bootsel_button() ==1: #if Bootsel button pressed then switch between colour and mono video
colourSM.active(not colourSM.active())
monoSM.active(not monoSM.active())
time.sleep(1)
EDIT: Above post fixed with pictures now displaying correctly
That is really nice. Excellent work.
Thanks for sharing 👍
Very interesting!!!
It would be great to be able to take advantage of this along with @Habi's board (https://www.habisoft.com/pcwwiki/doku.php?id=es:hardware:perifericos:pcw-io) to take advantage of the PCW boards that are loose.
That's pretty cool.
It would be nice if the button switched between different palettes (if blue is wired up eventually).
I imagine Locoscript looks a mess!
Cool expansion!!! :) :) :) Just awesome!!! :) :) :)
Can it be bought somewhere?
Quote from: GUNHED on 16:29, 10 January 25Cool expansion!!! :) :) :) Just awesome!!! :) :) :)
Can it be bought somewhere?
I have no plans to create and sell a board out of it.
Anyone is free to use this design to create their own board, i dont claim any rights for it or anything like that, and the components are all very cheap.
Well, if somebody is going to create this awesome expansion, please let me know. I would be interested in 2 units. Sadly I'm in time-troubles, so I can't do a batch by myself.
Quote from: Sykobee (Briggsy) on 14:12, 10 January 25That's pretty cool.
It would be nice if the button switched between different palettes (if blue is wired up eventually).
I imagine Locoscript looks a mess!
I have wired up Blue to create 8 colour mode (optionally 16 colour with the extra diodes and resistors as shown on the additional diagram). I dont seem to be able to modify the original post, so let me put the details in here:
3 different modes are selectable by pressing the Button on Pi Pico:
1. Standard Green on Black 720x256
2. 4 colour 360x256 (Black, Red, Green, Yellow - although you can get different colours if you connect the outputs to different RGB channels of your monitor)
3. 8 colour (optionally 16) 180x256
Schematic:
rgb.png
This is the option for 16 colour wiring i found online where the Intensity pin (Y0) is also connected. I don't have space on my breadboard to test it, but its fully implemented in software, should work as expected but the resistor values will need tweaking most likely:
16colours.png
Pi Pico code modified to support 2,4,8 and 16 colour modes:
import rp2
from machine import Pin,freq
import time
@rp2.asm_pio(out_shiftdir=1,out_init=(rp2.PIO.OUT_LOW,rp2.PIO.OUT_LOW, rp2.PIO.OUT_LOW,rp2.PIO.OUT_LOW,rp2.PIO.IN_LOW))
def video8colour():
wrap_target()
wait(1,gpio,22) # wait for end of Sync pulse
label("loop")
in_(pins,1).delay(15) # sample 1st bit then wait for 2nd bit
in_(pins,1).delay(15) # sample 2nd bit
in_(pins,1).delay(15) # sample 3rd bit
in_(pins,1) # sample 4th bit
mov(osr,isr).delay(0)
out(pins,4).delay(12)
jmp(pin, "loop") # jump back to Loop if still in active drawing area
mov(osr,x)
out(pins,4) # output all zeroes to the monitor as we are in the blanking area
wrap()
@rp2.asm_pio(out_shiftdir=1,out_init=(rp2.PIO.OUT_LOW,rp2.PIO.OUT_LOW,rp2.PIO.IN_LOW))
def video4colour():
wrap_target()
wait(1,gpio,22) # wait for end of Sync pulse
label("loop")
in_(pins,1).delay(15) # sample 1st bit for 2nd bit
in_(pins,1) # sample 2nd bit
mov(osr,isr)
out(pins,2).delay(12)
jmp(pin, "loop") # jump back to Loop if still in active drawing area
mov(osr,x)
out(pins,2) # output all zeroes to the monitor as we are in the blanking area
wrap()
@rp2.asm_pio(out_shiftdir=1,out_init=(rp2.PIO.OUT_LOW,rp2.PIO.IN_LOW))
def video2colour():
wrap_target()
wait(1,gpio,22) # wait for end of Sync pulse
label("loop")
in_(pins,1) # sample video
mov(osr,isr)
out(pins,1).delay(4) # output video
jmp(pin, "loop") # jump back to Loop if still in active drawing area
mov(osr,x)
out(pins,1) # output
wrap()
@rp2.asm_pio(out_shiftdir=1,out_init=(rp2.PIO.OUT_LOW,rp2.PIO.IN_LOW))
def sync():
wrap_target()
in_(pins,1) # sample Sync pulse
mov(osr,isr)
out(pins,1) # output Sync to the monitor
wrap()
freq(256000000)
colourSM = rp2.StateMachine(7, video4colour, freq=256000000,in_base=Pin(21),out_base=Pin(17),jmp_pin=Pin(22))
monoSM = rp2.StateMachine(5, video2colour, freq=128000000,in_base=Pin(21),out_base=Pin(17),jmp_pin=Pin(22))
fullcolourSM = rp2.StateMachine(6, video8colour, freq=256000000,in_base=Pin(21),out_base=Pin(16),jmp_pin=Pin(22))
syncSM = rp2.StateMachine(4, sync, freq=256000000,in_base=Pin(22),out_base=Pin(20))
syncSM.active(1) # start the Sync video initially
monoSM.active(1) # start the 2 colour video initially
current_mode = 0
while True:
if rp2.bootsel_button() == 1: # if Bootsel button pressed then switch between video modes
current_mode = (current_mode + 1) % 3
if current_mode == 0:
fullcolourSM.active(1)
colourSM.active(0)
monoSM.active(0)
elif current_mode == 1:
fullcolourSM.active(0)
colourSM.active(1)
monoSM.active(0)
elif current_mode == 2:
fullcolourSM.active(0)
colourSM.active(0)
monoSM.active(1)
time.sleep(1)
Finally, as screenshot from 16 colour game Astro Marine Corps (https://www.habisoft.com/pcwwiki/doku.php?id=es:nuevos:amc (https://www.habisoft.com/pcwwiki/doku.php?id=es:nuevos:amc)) displayed using 8 colour mode:
amc8colour.png
This is so cool! :) :) :)
Who'd have thought!...
This is amazing..
I'm havign real problems getting this to work with micropython - for some reason my pi pico (usb-c) board wont work with micropython after 1.14 and it seems this is too old to have the required libraries.
Does anyone have it as a compiled .uf2 to just upload to a pico?
Quote from: squelch41 on 23:34, 05 April 25I'm havign real problems getting this to work with micropython - for some reason my pi pico (usb-c) board wont work with micropython after 1.14 and it seems this is too old to have the required libraries.
Does anyone have it as a compiled .uf2 to just upload to a pico?
Solved it - had to compile with 1.22 - the 1.24 kept saying memory alignment error.
Here it is if anyone needs it:
(I dont think this forum supports direct attachments?)
https://www.dropbox.com/scl/fi/86331yoizp6q1qmx2vh5f/pcw-colour.uf2?rlkey=xqkybd9teew6hlflufr2pfw7u&st=f9mg85kv&dl=0
I'm not too familiar with the PCW video output, does it have 4 brightness levels like the Gameboy, or is it taking in pairs of adjacent pixels and treating them as a 2-bit number?
Does it work with regular PCW software or are you modifying those games in some way?
Quote from: Amagni on 01:40, 07 April 25I'm not too familiar with the PCW video output, does it have 4 brightness levels like the Gameboy, or is it taking in pairs of adjacent pixels and treating them as a 2-bit number?
Does it work with regular PCW software or are you modifying those games in some way?
The system here treats 2 pixels as 2 bit number.
Most games just work unmodified as graphics were ported from cga or cpc.
Quote from: czarnikjak on 08:40, 07 April 25Quote from: Amagni on 01:40, 07 April 25I'm not too familiar with the PCW video output, does it have 4 brightness levels like the Gameboy, or is it taking in pairs of adjacent pixels and treating them as a 2-bit number?
Does it work with regular PCW software or are you modifying those games in some way?
The system here treats 2 pixels as 2 bit number.
Most games just work unmodified as graphics were ported from cga or cpc.
That's awesome!
I need to order a Rpi Pico, then I'm definitely trying it out!
turns out using an alie
Quote from: squelch41 on 23:34, 05 April 25I'm havign real problems getting this to work with micropython - for some reason my pi pico (usb-c) board wont work with micropython after 1.14 and it seems this is too old to have the required libraries.
Does anyone have it as a compiled .uf2 to just upload to a pico?
Turns out using an aliexpress pi pico was the issue! used a pimoroni one and fine!
Quote from: czarnikjak on 11:44, 17 January 25I have wired up Blue to create 8 colour mode (optionally 16 colour with the extra diodes and resistors as shown on the additional diagram). I dont seem to be able to modify the original post, so let me put the details in here:
3 different modes are selectable by pressing the Button on Pi Pico:
Schematic:
rgb.png
This is the option for 16 colour wiring i found online where the Intensity pin (Y0) is also connected. I don't have space on my breadboard to test it, but its fully implemented in software, should work as expected but the resistor values will need tweaking most likely:
16colours.png
Hi just checking: is this schematic/ code working for scart or VGA or both?
Quote from: fuzzweed on 07:32, 04 May 25Quote from: czarnikjak on 11:44, 17 January 25I have wired up Blue to create 8 colour mode (optionally 16 colour with the extra diodes and resistors as shown on the additional diagram). I dont seem to be able to modify the original post, so let me put the details in here:
3 different modes are selectable by pressing the Button on Pi Pico:
Schematic:
rgb.png
This is the option for 16 colour wiring i found online where the Intensity pin (Y0) is also connected. I don't have space on my breadboard to test it, but its fully implemented in software, should work as expected but the resistor values will need tweaking most likely:
16colours.png
Hi just checking: is this schematic/ code working for scart or VGA or both?
It's 15kHz output - works for SCART.
I'd imagine would also work if you have a 15kHz capable vga monitor, but obviously, most don't support that scan rate
Ah OK. It was just the different pin labelling on the two schematics that confused me. Could a pico not manage 30k?
Quote from: fuzzweed on 13:45, 29 May 25Ah OK. It was just the different pin labelling on the two schematics that confused me. Could a pico not manage 30k?
Pico could. But the signal coming from PCW is not. I'm doing minimal processing here, for example the Sync signal is just passed through.
For VGA you would need to create your own SYNC timing and fit the pixel data coming from PCW into it. All Doable, but more complicated than this simple example.
Great stuff. Thanks for the info
I'm struggling to get this working properly -
I get video fine from the pico but if I run anything with grey scales eg head over heels, I cant see anything other than the bright white text. In the game, I can see the play character but not the lives or the pattern on the floor.
This is the same for any of the colour modes.
I've use 270ohm resistors on RGB, 1k on sync and 100ohm on RGB blanking.
Even if I bypass the resistors, the problem remains.
What am I doing wrong?
Quote from: squelch41 on 21:59, 01 June 25I'm struggling to get this working properly -
I get video fine from the pico but if I run anything with grey scales eg head over heels, I cant see anything other than the bright white text. In the game, I can see the play character but not the lives or the pattern on the floor.
This is the same for any of the colour modes.
I've use 270ohm resistors on RGB, 1k on sync and 100ohm on RGB blanking.
Even if I bypass the resistors, the problem remains.
What am I doing wrong?
Hard to diagnose remotely, I would check first if you are getting voltages from all R G B pins on the pico. Display something with all white pixels on the screen and check voltages on the pico output pins. But if you are getting white text I would expect it to work.
Also in normal 2 colour mode boot to cpm and see if text is green, then and try connecting G output from pico to R input on your RGB lead, see if you are getting red text, and try the same with B input as well to see if the text is blue. This should test all 3 channels.
Quote from: czarnikjak on 09:53, 03 June 25Quote from: squelch41 on 21:59, 01 June 25I'm struggling to get this working properly -
I get video fine from the pico but if I run anything with grey scales eg head over heels, I cant see anything other than the bright white text. In the game, I can see the play character but not the lives or the pattern on the floor.
This is the same for any of the colour modes.
I've use 270ohm resistors on RGB, 1k on sync and 100ohm on RGB blanking.
Even if I bypass the resistors, the problem remains.
What am I doing wrong?
Hard to diagnose remotely, I would check first if you are getting voltages from all R G B pins on the pico. Display something with all white pixels on the screen and check voltages on the pico output pins. But if you are getting white text I would expect it to work.
Also in normal 2 colour mode boot to cpm and see if text is green, then and try connecting G output from pico to R input on your RGB lead, see if you are getting red text, and try the same with B input as well to see if the text is blue. This should test all 3 channels.
Thanks - I'm getting red, green and blue output and the mode switch works.
When I 'scope the pins I get quite low voltages -
This is without anything connected to the pico, just the values after the resistors:
(Yellow is the green channel, blue is the sync pin - all taken on the head over heels start screen)
(https://www.cpcwiki.eu/forum/index.php?action=dlattach;attach=45355;image)
With the scart connected to a monitor, I get
(https://www.cpcwiki.eu/forum/index.php?action=dlattach;attach=45357;image)
I thought that if I bypassed the resistors, that might help but it doesnt make any difference.
This is the Head over Heels start screen as a photo of the monitor:
(https://www.cpcwiki.eu/forum/index.php?action=dlattach;attach=45359;image)
Silly question. Is it rgb capable monitor? Scart =/= rgb
Quote from: fuzzweed on 18:25, 03 June 25Silly question. Is it rgb capable monitor? Scart =/= rgb
Hehe, yes :)
Tried on my SCART scaler that I use for megadrive, snes etc with RGB scart cables and a Sony LCD TV which has a couple of other rgb scarted consoles
Quote from: squelch41 on 18:38, 03 June 25Quote from: fuzzweed on 18:25, 03 June 25Silly question. Is it rgb capable monitor? Scart =/= rgb
Hehe, yes :)
Tried on my SCART scaler that I use for megadrive, snes etc with RGB scart cables and a Sony LCD TV which has a couple of other rgb scarted consoles
Does the cable you use with the PCW have a voltage on the RGB detect pin?
That's a common issue on the CPC that the TVs don't switch to RGB mode.
You can bluff that with a battery. Put 1.5v on pin 16 should do it
Quote from: eto on 18:46, 03 June 25Quote from: squelch41 on 18:38, 03 June 25Quote from: fuzzweed on 18:25, 03 June 25Silly question. Is it rgb capable monitor? Scart =/= rgb
Hehe, yes :)
Tried on my SCART scaler that I use for megadrive, snes etc with RGB scart cables and a Sony LCD TV which has a couple of other rgb scarted consoles
Does the cable you use with the PCW have a voltage on the RGB detect pin?
That's a common issue on the CPC that the TVs don't switch to RGB mode.
Yes, it's in the schematic - 3.3v taken from the pico at pin 36.
I'm getting RGB as all the colours are visible - it just seems to either not be sampling the pcw signal correctly (so detecting the grays as black) or not outputting a strong enough signal to the scart (so essentially it is compressing down the levels) but I'm not sure which.
Or, it's something else that I am missing as a novice with analog video
Could that be over voltage? Just googling / guessing here, but rgb select says 1-3v