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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 28th Feb 2021, 11:43 am   #21
ortek_service
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Default Re: Reading PROMs with a Raspberry Pi

I presume these are the 0.64mm dia pins, designed to go into turned-pin sockets, so would be quite wobbly in breadboard if thinner than the average resistor lead. So the 0.64mm sides square pins would be a better fit (and also likely to provide two-sides of contact, rather than a single point, with round-pins).

Although it may also depend on quality / how well used the breadboard is, as may well suffer the problem of forcing too-large square-pins into IC sockets, which meant they wouldn't then work very-well with IC's (recently replaced one on a BBC Micro board, as ROM would fall out, without being taped down, it was that loose. So probably was one of the main faults with it).
Breadboard could often be rather intermittent, but you could often take the bottom off, and remove the contact strips to compress them back again / remove the bit of wire snapped off stuck in them!)
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Old 28th Feb 2021, 3:51 pm   #22
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Default Re: Reading PROMs with a Raspberry Pi

The 'Arduino jumper leads' which are widely available are primarily meant to go into the SIL sockets which are universally fitted to Arduino boards although they are rarely as snug a fit in there as I would like, and mostly a very slack fit in the average breadboard receptacle.

The 'Dupont' type, characterised by having 'hard' square connector bodies rather than rubbery round ones, are a much better friction fit in the two breadboards I have here so maybe they would be OK for the kind of breadboard lash-up I went for in my first round of experimentation. The project was really aimed at people who only have one PROM or set of PROMs to read, and who only need to be able to do it once.
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Old 1st Mar 2021, 10:40 pm   #23
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Default Re: Reading PROMs with a Raspberry Pi

You're not wrong about the jumpers. There's nothing worse than trying to do something for the first time with the wrong equipment - I really had no idea where to even start looking.

Buy cheap, you buy twice.

Colin.


Quote:
Originally Posted by SiriusHardware View Post
The 'Arduino jumper leads' which are widely available are primarily meant to go into the SIL sockets which are universally fitted to Arduino boards although they are rarely as snug a fit in there as I would like, and mostly a very slack fit in the average breadboard receptacle.

The 'Dupont' type, characterised by having 'hard' square connector bodies rather than rubbery round ones, are a much better friction fit in the two breadboards I have here so maybe they would be OK for the kind of breadboard lash-up I went for in my first round of experimentation. The project was really aimed at people who only have one PROM or set of PROMs to read, and who only need to be able to do it once.
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Old 2nd Mar 2021, 1:10 am   #24
SiriusHardware
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Default Re: Reading PROMs with a Raspberry Pi

Quote:
Buy cheap, you buy twice.
Maybe so. I've just been trying to replicate your Arduino Mega reading PROM reading exploits because I added a checksumming feature to the reader sketch, but thought I should probably check it before posting it.

Turns out there is some sort of problem with pins 28 (used for D0) and 31 (used for D4) on my Elegoo-branded Mega clone. It's never been hit with anything higher than 5V but those two pins are definitely out of order, they don't see a logic 1 input even when internal pullups are enabled and nothing else is connected. Annoying.

Would I be having this problem if the board had been bought from Arduino? Hard to say. In theory the circuit and parts are exactly the same.

Last edited by SiriusHardware; 2nd Mar 2021 at 1:17 am.
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Old 2nd Mar 2021, 2:14 am   #25
SiriusHardware
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Default Re: Reading PROMs with a Raspberry Pi

Oops, I owe Elegoo a grovelling apology. Nothing wrong with the board. I took it into my head to edit the hex character lookup table because I prefer my hex to be in upper case, and somehow managed to introduce an extra character.

Code:
const char hex[]=
{'0','1','2','3','4','5','6','7',
'8','8','9','A','B','C','D','E','F'};
You can imagine the strangeness that then ensued.

I finally twigged that although some (and only some) of the digits - sometimes the low nibble and sometimes the high nibble, sometimes both, were bizarrely offset by minus one, the checksum was always being displayed correctly - so the code had to be reading the PROM and adding the data up correctly, but not displaying it correctly.

Doh!
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Old 2nd Mar 2021, 9:42 pm   #26
SiriusHardware
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Default Re: Reading PROMs with a Raspberry Pi

Now that I have unbroken it, here (attached) is a slightly modified version of the Arduino Mega PROM reader sketch by OddBloke / Modified by OlivierM originally found by Slothie here:-

https://victorengineeringreloaded.wo...re-extraction/

I've added calculation and display of the 16-bit (summed) checksum, and I have also added a small function to always display 16-bit values as 4 hex digits, with leading zeros if needed. The Arduino...

Code:
Serial.print(value,HEX)
...statement has an annoying habit of printing only the significant digits of the value passed to it, so if you pass it 0x0001, it prints '1'. If you pass it 0x008F, it prints '8F', and if you pass it 0x0F12, it prints 'F12', and so on. You can't force it to print a specific number of digits. This was causing the width of the line address column at the left hand side of the displayed output to be inconsistent, so now the line addresses and 16-bit checksum are printed by a specific function.
Attached Files
File Type: zip PetPromReaderCsum_Mega.zip (1.9 KB, 57 views)
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