- #How to make a usb pic programmer serial
- #How to make a usb pic programmer full
- #How to make a usb pic programmer software
Not an approach I’d use, but it definitely does work.īack in the heyday of these chips, engineers spent a lot of time fretting about this stuff because FETs were rare exotica and the performance of available PNP transistors was quite poor. I’ve also seen people use opto-isolators to drive Vpp pins too. A simple divider circuit does the job just fine. The idea was a circuit which charges the gate as quickly as possible, without exceeding Vgs(max). The 11v Zener diode isn’t needed, and I haven’t included this on subsequent designs. It may well be possible to achieve comparable performance with a NPN+PNP transistor combo. In my case I’m using P-Ch FETs because Rds(on) is lower than comparable circuit using a small PNP transistor, which gives a faster and cleaner pulse, but it probably doesn’t matter. My design will work with PNP transistors in place of the FETs provided a base resistor is added (with the exception of Q6).
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Most common is NPN+PNP combo, works for most. There are quite a few different approaches out there. Constructing it as a MCM68764/MCM68766 programmer Constructing it as a dual type programmerĪll components must be fitted except for the RS-232 section.
#How to make a usb pic programmer serial
There is also a footprint for an RS-232 connection + MAX232 but this is not required for most applications as the Arduino can provide a serial interface through its USB port.
#How to make a usb pic programmer software
There is a software check to ensure this voltage is correct before powering on the EPROM. When programming 270x EPROMs, the Arduino must be supplied with a regulated +12V supply as the shield does not generate its own +12V rail.
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When built in its dual type form, selection between devices is made by a 6PDT switch, which software can query before powering on the device, checking against the selected device in the user interface, limiting the chance of accidentally blowing an EPROM (which will certainly happen if the switch is in the wrong position). When designing it I was aware that I was likely the only person that’d want something that did both, so have allowed for it to be constructed as a dual 270x/MCM6876x programmer, or 270x only / MCM6876x only. The only supported Arduino is the Mega 2560 R3 or compatible. Like the MCM68766 – they are algorithmically simple to program, so no complicated software stuff to worry about. This adapter typically supplies the extra voltages which aren’t practical to provide through the universal socket.
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Models that do support it, require a special adapter which doesn’t come cheap. All of these are required during programming – quite a headache for the designers of universal programmers.
#How to make a usb pic programmer full
+26V, +12V, +5V and -5V being the full list. It also needs the same high Vpp voltage, as well as an additional cocktail of voltages. This type of EPROM is genuinely more difficult to deal with. That having been said, there are some cheap programmers which support the 2716 EPROM, also needing a Vpp of 26V, so quite why MCM68766 is such a difficulty, may also depend on other things, such as pin arrangements, or perhaps just limited demand for it.
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Most cheap EPROM programms have a max Vpp of 13V. There is nothing algorithmically complicated about programming one of these – the main difficulty centres on the high Vpp voltage (26V). The original prototype – designed late 2016 and mentioned on forums early 2017 Why is MCM68766 difficult to program?