PiDP11 on the Pi 5

[isy...@gmail.com]

Hi All,

Having finally received my Pi 5 on Boxing day, I wondered if this device could be used in the PiDP11. One of the most obvious changes from previous models is the the GPIO register map has changed as there is a new interface chip (RP1) on this board. However, the kernel developers have caught up with this and implemented a driver that may be used via libgpiod.

I have re-written the two GPIO interface apps ... scanswitch and pidp1170_blinkenlightd to use this library. The updated files are available via this link:

https://drive.google.com/file/d/1LVLvaagOgXqNIiOmKtNpb1VS8aTeZsfS/view?usp=sharing

The apps have been tested using Bookwork 64.

Initially, I was concerned about the performance of this interface method in contrast to direct access to the GPIO registers as per the current build. But, I must say that it is not bad at all. This is partly offset by the Pi 5 performance which is such that the whole system now runs at ludicrous speed!!!!

In addition, it is quite possible that these updated apps may work at least on the Pi4 as the the kernel presents /dev/gpiochip0 which exposes the relevant GPIO lines. This would require a change of gpiochip4 to gpiochip0 in the apps.

NB: If you do decide to try a Pi5 in the PiDP11 case, I strongly recommend a heat sink with a fan! (Add some washers between the board and the nylon spacers or the fan may hit the PCB.)

Any feedback welcome, Ian.

[isy...@gmail.com]

NNB: Install libgpio-dev with sudo apt-get install libgpiod-dev before making the new apps.

[Steve Pitcher]

Thanks so much.  Not that I need it for anything... but I guess I just have to have the fastest PDP-11/70 in my neighborhood!  I pre-ordered the RPi-5 back in Sept and received it a while ago... and have been struggling with it since.  Perhaps 30 or 40 years ago I might have been up to the challenge of doing this work... but today I'm clearly not up to it.

I'll pull your two apps and give it a whirl, probably tomorrow.

- stp

[Steve Pitcher]

I said, tomorrow, didn't I?  Well, tonight's close enough.

It works great on the RPi5.  On the RPi4, it Seg Faults.  But the 5 is great.

Thanks.

[isy...@gmail.com]

Thanks. The segfault on the Pi4 is expected. Did you change gpiochip4 to gpiochip0 in gpio.c and scansw.c? I have just checked this and this works on the Pi 4.

BW, Ian.