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SIO2Pi (Banana flavoured)


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While archiving my collection it hit me: That Banana Pi I use at the bi monthly Retro meeting here in the Netherlands can also make use of the trick that The Montezuma used to connect a Raspberry Pi as a disk drive for the Atari. Up until now I dragged along SIO2PC device(s).


With the Raspberry Pi craze, several parties also wanted a piece of the pie. LeMaker came up with the Banana Pi, also a SoC, but with a little beefier specs, like gigabit ethernet, more RAM and a power switch. Another thing the Banana Pi has more of than the Raspberry Pi is four(!) UART interfaces. So, plenty of ways to connect to the SIO port. I picked the UART1, located on J12, as on the same row there is 3.3V and GND available, making it very easy to use a 4 pin connector I had lying around (an old CD Rom sound cable).


The PinOut of the Banana Pi, as you can see J12 consist of 2 rows with 4 GPIO pins, the top four (2,4,6, 8) being 3.3V, RXD, TXD, GND:


Details of all pins:



I haven't created a nice graphic representation of the connections, but the text version looks like this:

Connect Banana Pi J12 pins 2,4,6,8 to a level converter at its LV side. On the HV side of the level converter, connect a 1N581[789] Diode between the level converter and pin 3 of the SIO port. The connections should match below matrix:

*** Atari TO Level Shifter
SIO 3 (Data IN) - DIODE (1N581?) - HV1    * Via diode (for example 1N581[789]) direction from Atari to the level shifter *
SIO 5 (Data OUT) - HV2
SIO 10 (+5V) - HV

*** Level Shifter TO Banana Pi
LV1 - J12 Pin 6 (TxD)
LV2 - J12 Pin 4 (RxD)
LV - J12 Pin 2 (+3,3V)
GND - J12 Pin 8 (GND)

As you may notice, I did not connect SIO 7 (COMMAND), it should not be needed when you use sio2bsd or Respeqt. You can use the software attached to these posts on the Banana Pi as well. Depending on the linux distribution you use, it could be that your UART is connected to something other than ttyS3, to be sure, put an ATR on the SD card and use the following script to check 1. whether your cable works, 2. what terminal the J12 UART is connected to:

### Note: this runs as user root. If you are not running as root user, run 'sudo su -' first.
for DEV in {0..3}; do
  echo -e "\nTesting connection on ttyS${DEV}\n\n"
  sio2bsd -s /dev/ttyS${DEV} -f /root/atari/disks/demo/numen.atr

The output should be something like:

Testing connection on ttyS0

D1: 769 sectors, 196480 bytes total, mounted on /root/atari/disks/demo/numen.atr
PERCOM: trk 1, step 3, spt 769, heads 1, bps 256, flags 04 (SMALL-MFM-5.25INCH)
PCLink directory filter allows lower case names
Serial port: /dev/ttyS0
POKEY quartz 1781618.500000 Hz and HS Index 0 constant 7.186100 is assumed
Default speed: HSINDEX=40 (19200 bits/sec.)
Default turbo: HSINDEX=0 (123963 bits/sec.)
User selected: HSINDEX=0 (123963 bits/sec.) 

Next, power on the Atari connected to the Banana Pi. If your cable works and the script arrived at the correct terminal, you should see something like:

0 -> 'S': $31, $53, $0000 ($84)
3 -> 'R': $31, $52, $0003 ($86) 

If not, on the Banana Pi terminal, press CTRL+C and reset the atari from the Self Test screen (at the READY prompt, type 'BYE' and at the green screen press RESET). If your machine doesn't boot for the selected floppy, check the connections between the Pi and the Atari, verify if the floppy file on the Banana Pi exists and can be accessed (sio2bsd will display an error if it can't open the .atr file).


If you want to be really fancy, create a second cable and connect it to another UART and use the banana pi as a terminal for bbs access at the same time.


Hope that you too can put that Banana Pi to good use now.


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