working Backplane for the Pidp1

[Matthias Barthel]

i have build in the last weeks a functionally Backplane to connect some hardware to the pidp1.

the software on the Backplane musst be optimized because in full speed the esp32 have problems to handle the data from the pidp1.

slow data transfers are working good.

the backplane is connected via wlan and communicate over tcp-port 7200 with the pidp1.

at this time some prototypes of cards exist, and one led-card for outputting the 18 bits of IO and the 12 bits of the AC.

here is a short video of the backplane :

https://youtu.be/HiB_G6IKBR4

on the left side the 3 mcp-expander are for the data of AC and IO, on the right side is the "address-decoder" for all 64 addresses.

with this backplane you can connect 16 devices to your pidp1 , a option to cascade this to 32 devices is possible with a adapter between 

the backplane-controller and the backplane-connector-pcbs.A card for a lineprinter , a drivercard for relays and a keyboardcard ist in work.

the backplane is most compatible to the dynamic-iots from BIll, but its not tested yet.i think about a mix of my modificatins and bills,

when the iot is not configured in the pidp1-code, and no dynamic-iot-device is availible the dynamic-iot-controller sends the data to the backplane ...

i forgot to add some statuslights, to see if the backplane has a problem with the connection to the wifi or the tcp-port - this comes later ...

when the time is ready, the code and the gerber are on my github. if anyone is interessted i can build some kits to build this modification.

Matthias

[Bill E]

Excellent!. Have you tried spi? It's faster, but of course using tcp would probably be best.

I'm glad there are at least a few of us working on making our pidp-1's more generally useful.

Bill

[Matthias Barthel]

The data Transmission from the pidp1 to the backplane is over the tcp-port 7200, the pins of the backplane are over spi bus.

I think the wifi is the thing that slows down the backplane. But the pidp1 had no free spi ports, thats the reason why i implement the wifi. 

I will try a peer to peer ethernet connection from the raspberry to a wt32-eth01 Module, i think its much faster and stable. I dont know if its usefull ton send and receive the data over the serial pins of the raspberry, incan imagine that this is much to slow...

Matthias 

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[Bill E]

From a PDP-1 programming point of view, using the DCS IOT 22 support for sockets should work quite well for this. It's only a few instructions to establish a socket connection, then the I/O is equally simple, one IOT to read a byte, one to write a byte, and one to check the ready status. Again, this pretty closely follows the DEC DCS implementation, once you get a socket opened.

There is a lot of additional functionality, but for simple things, not needed.

Bill