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To: Michael Sperber <sperber@deinprogramm.de>
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From: Hal Murray <hmurray@megapathdsl.net>
Subject: Re: Can't get 11.0-RELEASE to boot on Banana PI M3
In-Reply-To: Message from Michael Sperber <sperber@deinprogramm.de>
 of "Fri, 25 Nov 2016 11:03:27 +0100." <y9loa13ub9s.fsf@jellaby.local>
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sperber@deinprogramm.de said:
> Ah, thanks ... but that's not standard RS232, right?  (BPI homepages says
> "TTL".)  If it isn't, what kind of hardware connects to that? 

The normal setup for RS232 is that the transmit and receive signals come out 
of a big chip (SOC, or PCI UART, or USB UART, or ...) and then go through a 
level converter which is typically a MAX-232 or one of many clones or 
variants.  The "TTL" is telling you that it doesn't have that level converter 
chip.

You can either add a level converter chip and then plug it into a real RS-232 
port, or find some setup that also doesn't have the level converter and 
speaks TTL levels.  Adafruit and probably many others sell a USB UART without 
the level converter for applications like this.
  https://www.adafruit.com/product/954

Sometimes, TTL means 3V CMOS levels and 5V from real TTL/CMOS will fry your 
expensive chip.  Best to check carefully.  The above part says 3V.  It also 
has an extra power wire that you get to ignore.


-- 
These are my opinions.  I hate spam.