Paneldue autonomous SD card playback
Would it be possible to mod a paneldue such that the MCU can read the SD card on the panel and play Gcode files over the UART interface?
That would allow longer wiring when using the panel SD card socket without the noise concerns of long SPI cables.
In fact with a bit of rs422 conversion at each end you could go for really long cables
Silly idea? (I have no idea if any spare SPI capable pins are available on the MCU or indeed if there's the spare horsepower)
You would need to use a high baud rate to make sure that the gcode commands arrived fast enough - I don't think the standard 57600 would be fast enough. That in turn would mean you definitely needed the RS422 conversion. It would be simpler just to convert the SPI signals to RS422 at both ends of the ribbon cable.
Very few people use the external SD card socket, because it's generally easier to upload files over the web interface than to move SD cards between machines.
I'm one of those weirdos using a smoothieboard and trying to jam a panedue onto it, though. So I'd quite like to be able to write to the the SD card on a PC then plug it into the panel and send a file due to the slow native SD write speed on smoothie.
Out of interest, are there spare pins that could run the SPI and does the CPU do much when not actively dealing with screen touches and updates? I might have a go myself
There are certainly some spare pins on the SAM3S processor, but only 3 of them are brought out to pads. I don't know whether the SPI pins or the USART pins (the USART can also do SPI) are free. See https://github.com/dc42/PanelDue/blob/master/PCB/V2.0/schematic-2.0.png for the schematic.
I suspect you will find that there is insufficient flash and/or RAM spare in the standard ATSAM3S2B version of PanelDue to add FATFS or similar code. However, you may be lucky enough to have the ATSAM3S4B version, which we originally produced for OEMs but eventually moved all of our production over to. That has 128Kb more flash and 16K more RAM than the standard version.
Or you could buy a Duet.
Or you could buy a Duet. ?
where's the fun in that though
OK, I'll take a look at the pins, hadn't thought about RAM … I have the 3S2B unfortunately.
If you have hot air soldering equipment, you could swap it for a 3S4B, or even a 4S4B or 4S8B.
PS - I have one PanelDue board fitted with a SAM4S8BA chip that I could be persuaded to part with for not very much. It won't run the standard firmware, but you are going to change the firmware anyway, and I can tell you what changes you need to make to support the 4S8BA because I already did that.