One friend of mine has such circuit. It needs some minor fixings on the 3,3v conversion, but he has little time now as he is teacher on the University.

On the tests we made it worked perfectly on input or output access on Basic programs, but not on half-duplex due to an error on Basic.

I can't say you a date of release, but probably before next Summer....

This is the first prototype.

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But it has a number of errors:

-The EDGE connector is mirrored. A cable was used instead.
-The footprint for the CH340G has to be narrower, it hardly coincides with the chip's legs.
-The CH340G should be feed with +3,3v and the levels of RX and CTS be with pull-up to +3,3v instead of +5v.

What the circuit does is to standardise the Enterprise serial signals to TTL compatible or to USB serial.

The CH340G chip is used on some USB serial adapters, and fits the Enterprise because it manages the two data signals and also the two handshake signals.

The 74LS06 and some diodes and resistors are used to invert and adapt the Enterprise levels.

Good stuff. Wifi on the Enterprise? That would be cool!! I see that the 74LS06 is used inside the Enterprise to drive the serial line, so seems like a good choice.


I haven't yet done anything about investigating USB, but I have managed to hook up the Enterprise serial port to an Amiga, which has a good old RS232 port. Data transfer works but I can't seem to get handshaking working (maybe because I'm not using the offset ground?)

If I enable handshaking on the Amiga, then it doesn't send anything to the EP.
If I disable handshaking, I can send up to 24 bytes at a time to the EP but then have to wait (that's the limit of EP buffering).

Writing data from EP to Amiga seems to work though.

When you say machine code - do you mean writing directly to the port 0B7h?

I'm using the standard EXOS SERIAL: device, which I think works the same whether used from BASIC or machine code.

As far as I can tell, the STATUS OUT line is +12v when the Enterprise is ready to read data, but for some reason nothing gets sent (or at least nothing gets received!). Sadly I can't really see what's going on because I only have a voltmeter, not an oscilloscope.

I was using this... OPEN £1:"SERIAL:"
COPY FROM £1 TO £0

That seemed to work ok, but because there was no handshaking I could only transfer 24 bytes at a time.

Maybe I'll give it a go from machine code.

Unfortunately my problem is not the Enterprise reading, but it's the other computer sending.

Without handshaking, the other computer can only send 24 bytes at a time - otherwise the Enterprise's buffer will become full and bytes will be lost - whether I'm using BASIC or machine code.

So I either insert a delay after sending every few bytes (at the Amiga/PC end) to give the EP enough time to process it's buffer; or else I really need to find out how to get handshaking working.

Some USB/Serial dongles don't support hardware handshake lines at all, some do RTS/CTS, some very sophisticated ones even support DSR/DTR. For those that support the hardware lines, you need to have a proper driver that supports hardware handshake as well (The USB stick needs to convert the pin change to a USB handshake packet and send that to the host and vice versa)

So, the first questions is: Does the chipset on the dongle support hardware handshake? The most common chips known to do that are FTDI USB/Serial chips. In case your dongle has one (and not a cheap Chinese rip-off), chances are high it works.

Another common chip range is the Prolific 2303 - Of these, only the SA, HXD and RA variant seems to support hardware handshake. The others don't (Those are mostly intended for printer interfaces only).

That is the first step to success - The next one is if the Dongle maker managed to expose the hardware handshake lines from the chip - Some do, some don't.

And the next step is whether you got a proper USB driver on the host computer that supports Hardware Handshake. Again, some do, some don't.

Best check very carefully the above points in the product description before you buy such a dongle to get HWHS to work

Tobias