Can't get 11.0-RELEASE to boot on Banana PI M3

[Ian Lepore]

On Fri, 2016-11-25 at 08:42 -0800, Rodney W. Grimes wrote:
> > 
> > 
> > sperber at 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.
> Be SURE to ignore that extra power wire!  If your USB/Serial adapter
> also has
> a power wire DO NOT CONNECT IT.  Many of these embeded boards provide
> a power
> pin with the serial interface that can be used to power something
> external,
> like a level shifter, and many of the USB/Serial adapters also bring
> out the
> USB 5V rail on a wire.  DO NOT CONNECT THE TWO! 
> 

Ummm... say what?

I power my rpi boards using the 5v power from the USB serial adapter
connected to the 5v pin on the rpi header.  I can't imagine any reason
not to.

> That being said, there are many aftermarket USB/Serial cables
> avaliable,
> usually a 3.3V version of these well work everywhere as long as it
> has
> 5V tolerent inputs, which most of the newer ones do, check the specs
> from the vendor.  3.3V outputs well satisfy the input requirements of
> a 5V TTL/CMOS circuit and not cause it problems, the opposite is not
> always true.
> 

Usb serial adapter based on Prolific chipsets are NOT 5v tolerant.
 Those based on FTDI chips are.  Those are the two big names in usb-
serial chips, but there are others out there too; you have to check the
datasheet to be sure.

> Watch your lead length and wire sizes if you need to do anything
> funny
> to get this connected, capacitive loading of any kind on this type of
> signal can cause character loss, especially at speeds above 9600
> baud.
> 

Ummm... that sounds pretty bogus too, considering that I've run ftdi
chips at 12mbps using breadboards with a rat's nest of wiring to carry
the comms signals to other boards.

-- Ian