[E3-hacking] Universal E2/E3 serial interface design

[mark]

Ian Stirling wrote:
> Andy wrote:
>> Hiya,
>>
>> As per my earlier posting I've now designed and built a universal
>> E2/E3 interface board that should convert to/from legal RS232 levels.
>> A jumper is used to select E2 or E3 mode. I've also produced a
>> circuit diagram from my prototype and put this here:
>>
>> http://www.cambridgewargames.org.uk/members/andy/emailer/
>>
>> I would welcome any feedback on the design and would also appreciate
>> people sanity check I've not put any stupid mistakes in the circuit
>> diagram when copying from my stipboard prototype.
>>
>
> The 1K resistors are not quite adequate protection on the input of IC1A.
> A static spark could easily generate 2Kv, or a 2A pulse.
> This will probably not kill the 4070 the first time.
>
> Four diodes, one each between the tip/ring connections, and VCC/ground
> would be a good idea.
> 1Nn4148 or similar would be fine.
>
>
>
>
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>
Hi,

Is it really necessary to adapt the voltage levels for the E3?

I know its the sane thing to do but I've been extracting the flash for
about 3 days now :(
with a direct serial connect between a standard 9 pin serial and the EXT
port and it has been fine.


Mark.