Home  |  Contents 

Microcontroller and PC projects
  Forum Index : Microcontroller and PC projects         Section
Subject Topic: HDMI output from MM2/MM+: interesting? Post ReplyPost New Topic
Page of 2 Next >>
Author
Message << Prev Topic | Next Topic >>
matherp
Guru
Guru


Joined: 11 December 2012
Location: United Kingdom
Online Status: Offline
Posts: 2340
Posted: 05 October 2018 at 8:56pm | IP Logged Quote matherp










Using MMBasic running on Pi-Zero as an HDMI I/F for a MM2.
A loadable CFunction display driver on the MM2 (running completely standard MMBasic) communicates over a 4-bit parallel I/F to the Pi-Zero. This is also running MMBasic with a new feature OPTION REMOTE ENABLE which tells it to listen on the 4-bit port for graphics commands.

Surprising, the Pi is very poor at acting as a slave device and receiving high volume data but using the 4-bit i/f I'm getting a reasonable throughput.

Reliability isn't there yet as the Pi seems to crash out of MMBasic after 5 minutes or so but this could just be a wiring issue.


Edited by matherp on 05 October 2018 at 8:59pm



Back to Top View matherp's Profile Search for other posts by matherp
 
Grogster
Guru
Guru
Avatar

Joined: 31 December 2012
Location: New Zealand
Online Status: Offline
Posts: 6128
Posted: 05 October 2018 at 9:20pm | IP Logged Quote Grogster

You don't rest for long before coming up with something else, do you?

This is neat. But if you had to have an HDMI output for your MM, surely there are HDMI host chips that can be had these days?

Perhaps not. I know HDMI licensing is a little complicated.

__________________
Smoke makes things work. When the smoke gets out, it stops!
Back to Top View Grogster's Profile Search for other posts by Grogster Visit Grogster's Homepage
 
matherp
Guru
Guru


Joined: 11 December 2012
Location: United Kingdom
Online Status: Offline
Posts: 2340
Posted: 05 October 2018 at 9:32pm | IP Logged Quote matherp

Quote:
surely there are HDMI host chips that can be had these days?


Possibly, but you also need a framebuffer, a PCB layout, build and debug etc.....

A Pi-Zero does all this for you for a fraction of the price
Back to Top View matherp's Profile Search for other posts by matherp
 
Grogster
Guru
Guru
Avatar

Joined: 31 December 2012
Location: New Zealand
Online Status: Offline
Posts: 6128
Posted: 05 October 2018 at 9:36pm | IP Logged Quote Grogster

Yes, good point.

__________________
Smoke makes things work. When the smoke gets out, it stops!
Back to Top View Grogster's Profile Search for other posts by Grogster Visit Grogster's Homepage
 
goc30
Senior Member
Senior Member
Avatar

Joined: 12 April 2017
Location: France
Online Status: Offline
Posts: 106
Posted: 06 October 2018 at 1:14am | IP Logged Quote goc30





very good idea




Back to Top View goc30's Profile Search for other posts by goc30
 
JohnS
Guru
Guru


Joined: 18 November 2011
Location: United Kingdom
Online Status: Offline
Posts: 1689
Posted: 06 October 2018 at 2:39am | IP Logged Quote JohnS

Are you in effect bit-banging at the Pi end?

Either way, roughly what sort of throughput (*) can you reliably get?

Probably some follow-up questions/ideas depending on the above...

(*) not sure what units make sense: 4-bit transfers per second? MB/s?

John
Back to Top View JohnS's Profile Search for other posts by JohnS
 
matherp
Guru
Guru


Joined: 11 December 2012
Location: United Kingdom
Online Status: Offline
Posts: 2340
Posted: 06 October 2018 at 4:06am | IP Logged Quote matherp

Are you in effect bit-banging at the Pi end?


Nibble banging

Quote:
Either way, roughly what sort of throughput (*) can you reliably get?


A 14 byte message takes 75 micro-seconds so 187Kbytes/second when active
Back to Top View matherp's Profile Search for other posts by matherp
 
JohnS
Guru
Guru


Joined: 18 November 2011
Location: United Kingdom
Online Status: Offline
Posts: 1689
Posted: 06 October 2018 at 4:52am | IP Logged Quote JohnS

Thanks.

Would it be better to use an ordinary channel - UART, or whatever?

That way Linux already has a device driver and there may be hardware buffering so overall better throughput / less CPU load.

Does depend on what the MMS/MM+ has available as well as what the RPi has...

John
Back to Top View JohnS's Profile Search for other posts by JohnS
 
matherp
Guru
Guru


Joined: 11 December 2012
Location: United Kingdom
Online Status: Offline
Posts: 2340
Posted: 06 October 2018 at 5:03am | IP Logged Quote matherp

Quote:
Would it be better to use an ordinary channel - UART, or whatever?


UART is no good as the "proper" UART on Pi's with Wifi is used for Bluetooth. The other one has a baudrate that varies with CPU clock speed (very useful - not)

SPI would be the obvious one but no-one has ever got a Pi to work in SPI slave mode. This uses some "special" I/F H/W (bsc)

I2C too slow and uses the same I/F as SPI, does work sort of but not reliable.
Back to Top View matherp's Profile Search for other posts by matherp
 
JohnS
Guru
Guru


Joined: 18 November 2011
Location: United Kingdom
Online Status: Offline
Posts: 1689
Posted: 06 October 2018 at 6:47am | IP Logged Quote JohnS

Oh.

Sorry, was just a thought.

Er, do you change the CPU clock speed often?

John
Back to Top View JohnS's Profile Search for other posts by JohnS
 
matherp
Guru
Guru


Joined: 11 December 2012
Location: United Kingdom
Online Status: Offline
Posts: 2340
Posted: 06 October 2018 at 7:38am | IP Logged Quote matherp

Quote:
Er, do you change the CPU clock speed often?


I don't but Rasbian does it behind your back in response to thermal /load etc.
Back to Top View matherp's Profile Search for other posts by matherp
 
MicroBlocks
Guru
Guru
Avatar

Joined: 12 May 2012
Location: Thailand
Online Status: Offline
Posts: 2190
Posted: 06 October 2018 at 4:09pm | IP Logged Quote MicroBlocks

Use a 1455 as a Serial/SPI/Parallel input at the mm side and USB CDC or HID at the Pi side and get a pretty high throughput.

You could use that also to create a 'window' on a windows/Linux machine that can act as a remote screen. (Got that working already, but it is not open source as it is made for a client so can not share).



__________________
Microblocks. Build with logic.
Back to Top View MicroBlocks's Profile Search for other posts by MicroBlocks
 


Page of 2 Next >>
In the news...
 
Post ReplyPost New Topic
Printable version Printable version
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Powered by Web Wiz Forums version 7.8
Copyright ©2001-2004 Web Wiz Guide

This page was generated in 0.1094 seconds.
Privacy Policy     Process times : 0, 0, 0, 0.11