| Z80-SBC by Scott Baker, info needed. [message #9356] |
Sat, 06 November 2021 11:52  |
guus.assmann
Messages: 50
Registered: May 2018
Location: Netherlands
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Member |
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Hello,
One of my many projects is an SBC, designed by Scott Baker.
Unfortunatelly, the data seems to be incomplete, as I cannot find the values in the BOM.
A query on his website has not helped. Maybe he's bussy elsewhere....
The components I would like to know values for are:
R11, RN3, 6, 7, 8, 9, SV3, SV4, RN14, RN15 and both oscillatores OG1 and OG2.
Of course the oscillators determine baud-rate for the Duart and clock for the CPU, but still I'd like some recommendations.
BR/
Guus Assmann
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| Re: Z80-SBC by Scott Baker, info needed. [message #9362 is a reply to message #9359] |
Sun, 07 November 2021 01:45  |
speed3ple
Messages: 1
Registered: March 2020
Location: Norway
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Junior Member |
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Hi Guus
I did build this sbc some time ago, maybe I can be of some help.
See my attempt here:
builderpages:speed3ple:z80-trainer
The design files from Mr Baker did seems to lack some info about values and I might have gotten it wrong, but my board booted with these values:
R11 = 10K (This is just for fine tuning the 555 freq, so I used R11+R12=10K and R17=100K)
RN3 (for the LEDS) = 471
RN6, 7, 8, 9(Pull up resistors for keypad)= All 10K, I didnt have the correct pins on the RN9 so i simply cut it to length and measured it before soldered in.
SV3, SV4 = I never used or installed components at these ports, but I have marked 2K2 for the resistors on my buildpapers, sorry.
RN14, RN15 = If You refer to RN4+RN5, I used 471. (I looked at the Zeta 2 design and just took a chance here...
oscillators:
OG1=7.372Mhz
OG2=1.8432Mhz
I use these jumper settings:
JP2=ON (CPU Osc ON)
JP4=short 3+2 (determines UART osc is being used, OG1+divider or OG2?
JP1=OPEN (LCD screen)
S1=All OFF
For IC7+IC16 i used ATF16v8 and burned them with the new MiniPro. I did struggle with this.
TTL logic, I used AHCT/HCT to minimize current. (132+670 is HCT)
I tested the keypad/pullup resistors via a simple basic program for detecting the keypad number input and it seems to work fine.
What I never got to work was to compile a new RomWBW for this (bc I wanted to try to connect the RC2014 bus to a IDE/CF storage like I did with the excellent EasyZ80 design by Mr. Kiselev).
I did try to recompile the RomWBW version from Mr Baker site with some different options, but I not succeed, got a lot of error messages.
I also didn't manage to set the baud rate at anything other than 115k, probably due to my lack of understanding how to handle the CTC chip/divider?
OBS! The voltage regulator gets very hot if used this board with TIL311's, so I quickly switched a LCD. I think the TIL311's looks a lot better!
I have 3 PCB's in my box if anyone is interested.
Please share any progress on this project! 
All the best
Svend
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