[E3-hacking] About connecting to the serial on the E3

Wed Apr 3 20:51:53 BST 2019

OK, thanks, I was looking at this site.. http://www.cambridgewargames.org.uk/members/andy/emailer/

It says on here 3.3v device so was guessing it would work but I don’t understand the inverting the TX Line, would I need to do that with this..? I was reding this…

”Amstrad emailer E3 serial port (18/01/06)

A fair bit of confusion exists on the serial port of the E3 with some sources saying a line driver chip is needed, and other saying one is not needed, to connect this to a PC.

I've spent a bit of time looking at this and can now offer some explanation. A normal RS232 port will transmit a digital 1 as a negative voltage, usually at least -5V. A 0 is transmitted as a positive voltage, typically at least +5V. The emailer does not do this. Using a rather old poorly calibrated scope it appears to actually transmits either 0V or +5V.

Now some serial ports will probably accept this, but a 0V input is not a logical anything as far as the RS232 spec is concerned. So your PC, like mine, may ignore this. The fact that this works for some peoples PCs implies it is transmitting a logical 1 as 0v and a logical 0 as +5V.

A typical RS232 line driver expects a logical 0 to be 0v and a logical 1 to be +5v (or +3.3V if using a 3.3v device). So you end up with an inverted RS232 data and like me and see horrible gibberish on hyperterminal

Now, to get a boot log you need to invert the TX signal from the E3 (I used a 74HC04) then pass this to a line driver chip. The only line driver chip I had to hand was a MAX3233E, which is a 3.3 volt part. For this reason I ran both chips from 3.3V and placed a 100ohm resistor between the E3's TX pin nad the input to the inverter. Some logic families get very upset if you exceed the supply voltage on an input by more than about 0.6v... The series resistor limits the current and is a paranoia measure, quicker than looking up the datasheet :-) Anyway, it was a horrible quick bodge but it worked.

Here is the output captured from hyperterminal boot.txt<http://www.cambridgewargames.org.uk/members/andy/emailer/boot.txt> settings were 115,200 8n1 no handshaking.

I'll try and post up a diagram of something better in the next few days. I've also built something for the reverse direction but havent had a chance to work out if its working yet....”

I do have one made by FTDI too a FTDI FT232RL FT232 USB to TTL 5v 3.3v serial adaptor that has 3.3 v and 5v, it has a jumper to change voltage on RX Line, what about that one..? https://www.xcluma.com/ftdi-ft232rl-ft232-usb-to-ttl-5v-3.3v-serial-adaptor-for-arduino
There is no info on using one of theses because in 2006 they didn’t exsits.. 😊
They exist now because of Raspberry PI and Arduino, The Amstrad Emailer uses a singer board computer inside it, The RPI and Arduino are what has become of the technology the Emailer uses. The mini consoles use the technology too.

Spanner..

From: David Given<mailto:dg at cowlark.com>
Sent: ‎Wednesday‎, ‎3‎ ‎April‎ ‎2019 ‎19‎:‎57
To: Discussion of the Amstrad E3 emailer hardware/software<mailto:e3-hacking at earth.li>

RS232 is actually +/- 12V! My recollection is that the E3 runs at 0V/5V (I described it as TTL back in 2003). A 3.3V serial converter might work, I couldn't say.
On Wed, 3 Apr 2019 at 20:52 Nick Griffin <span1922 at live.com<mailto:span1922 at live.com>> wrote:
On your site..
“In order to talk to the E2, you need the appropriate cable. Irritatingly, while the E2 has a serial port, it runs at TTL line levels not RS232 levels. This means that if you're going to connect it to a PC, you need a line level converter”

So I can use a CPC 2102 USB to TTL serial converter because its a line level converter… 😊 and its RX line is 3.3 volt, this can’t take 5 volts because it could blow the UART0…?

Spanner..

From: David Given<mailto:dg at cowlark.com>
Sent: ‎Wednesday‎, ‎3‎ ‎April‎ ‎2019 ‎18‎:‎52
To: Discussion of the Amstrad E3 emailer hardware/software<mailto:e3-hacking at earth.li>

I've got a tool which speaks the PBL protocol and will let you read and write the flash: http://cowlark.com/amstrad/<https://nam03.safelinks.protection.outlook.com/?url=http://cowlark.com/amstrad/&data=02%7c01%7c%7c09f58ed443864a97d08808d6b86632a2%7c84df9e7fe9f640afb435aaaaaaaaaaaa%7c1%7c0%7c636899146427885270&sdata=ZTUttHYZe8W%2Bp6P%2BIDBCIg1vQDqKRwzM9y4Mrf%2B4HAw%3D&reserved=0>

It's also got details of the serial pinout.

On Wed, 3 Apr 2019 at 19:07 Nick Griffin <span1922 at live.com<mailto:span1922 at live.com>> wrote:
As far as I know when you connect this to serial you don’t get a console, like if you connect TheC64 Mini to Putty using a CPC 2102 USB to TTL serial convertor, you can log on with your root user and password so you can add files, change games and edit files and that ,TheC64 Mini uses Uboot to boot up with not PBL so it must be the PBL that's stopping the console coming up so if we could hack the PBL (Primary Boot Loader) and keep the firmware on the NAND so its still boots up with Amstrad E3 logo and that, we need to see the system files and see what can be changed. PBL is on the NOR Flash and the Kernel and System is on the NAND Flash. I don’t know anything about PBL so we need someone who does.it<https://nam03.safelinks.protection.outlook.com/?url=http://does.it&data=02%7c01%7c%7c09f58ed443864a97d08808d6b86632a2%7c84df9e7fe9f640afb435aaaaaaaaaaaa%7c1%7c0%7c636899146427895281&sdata=m1xYQJZEIyNyS4SWf7kDZ%2BZO6CGhFKUgU3%2BBedRPN3I%3D&reserved=0> all most works the same as TheC64 Mini,(Its a small Commodore 64, Mini Console, its here.. https://www.c64-wiki.com/wiki/THEC64Mini<https://nam03.safelinks.protection.outlook.com/?url=https://www.c64-wiki.com/wiki/THEC64Mini&data=02%7c01%7c%7c09f58ed443864a97d08808d6b86632a2%7c84df9e7fe9f640afb435aaaaaaaaaaaa%7c1%7c0%7c636899146427905286&sdata=lecxYohNL06ij7PeSWsWCsz4fEUgCHizc0HgJXTo%2Buc%3D&reserved=0>)  The mini has 2 partitions, One for Uboot and other for the Kernel and System. but only has one chip, NAND Flash, its made by Toshiba too.. 😊. Amstrad E3 has 2 chips NOR and NAND Flash. and is using a different Boot loader.

Oh.. Can I use my CPC 2102 USB to TTL serial converter to connect to the serial on the E3..? this is a pic of it here.. https://sc02.alicdn.com/kf/HTB11eb9PFXXXXcLaXXXq6xXFXXXd/CP2102-USB-2-0-to-TTL-UART.jpg_350x350.jpg<https://nam03.safelinks.protection.outlook.com/?url=https://sc02.alicdn.com/kf/HTB11eb9PFXXXXcLaXXXq6xXFXXXd/CP2102-USB-2-0-to-TTL-UART.jpg_350x350.jpg&data=02%7c01%7c%7c09f58ed443864a97d08808d6b86632a2%7c84df9e7fe9f640afb435aaaaaaaaaaaa%7c1%7c0%7c636899146427915291&sdata=KroTh2plWQe%2BxRae/OKV%2BnUB/C%2BXTMrTgayWOyOxHR0%3D&reserved=0> I have used it on my TheC64 Mini and my Gotek Drive.

Spanner..
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