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by tgritchie
Fri Aug 25, 2017 12:33 pm
Forum: Bare metal, Assembly language
Topic: Act LED (hello world)' Programming on RPi 3 (BCM2837)
Replies: 19
Views: 5744

Re: Act LED (hello world)' Programming on RPi 3 (BCM2837)

The only minor difference I see from my code is in the GNU asm .ld file where my version places the _start code in the .init section. However I don't think this should make much difference especially given that the FASMARM version seems to produce the same code. Two other things you could check is t...
by tgritchie
Tue May 03, 2016 7:49 pm
Forum: Bare metal, Assembly language
Topic: Act LED (hello world)' Programming on RPi 3 (BCM2837)
Replies: 19
Views: 5744

Re: Act LED (hello world)' Programming on RPi 3 (BCM2837)

Trevor - If you are able to turn the RPi3 red LED off, would you please post how you do it? Ahnjoan As I said before the code is available further into the quoted post but here it is anyway :-) ; format binary as 'img' format ELF as 'elf' org $0000 ; Return CPU ID (0..3) Of The CPU Executed On mrc ...
by tgritchie
Sat Apr 23, 2016 2:08 pm
Forum: Bare metal, Assembly language
Topic: Act LED (hello world)' Programming on RPi 3 (BCM2837)
Replies: 19
Views: 5744

Re: Act LED (hello world)' Programming on RPi 3 (BCM2837)

3. In this thread , the user gregeric commented "On the Pi3B the red & green LEDs are no longer connected to bcm GPIOs; instead they are driven from an i2c GPIO expander: U20 located near the DSI connector." If this is the case for RPi 3, how can I program I2C GPIO expander, to control on board LED...
by tgritchie
Tue Jun 30, 2015 11:34 am
Forum: Bare metal, Assembly language
Topic: Boot code from SD card (other possibilities)
Replies: 8
Views: 1261

Re: Boot code from SD card (other possibilities)

Hi - I, too, started out with dwelch67s serial bootloader code to avoid the tedium of swapping SD cards in and out but now use Jamie Iles' remote debug code which not only allows loading of images thru the serial port but also some (admittedly limited) debugging using GDB. Check it out here: https:/...
by tgritchie
Wed Jun 18, 2014 11:19 am
Forum: Bare metal, Assembly language
Topic: beginner questions
Replies: 6
Views: 1787

Re: beginner questions

Hello - I too started by using David's boot loader to avoid the SDCARD "dance" but soon moved on to a remote stub for the GDB debugger that I found here: https://github.com/jamieiles/rpi-gdb. This allows you to not only download .elf images into the pi but also enables some (admittedly fairly limite...
by tgritchie
Wed May 07, 2014 7:34 pm
Forum: Bare metal, Assembly language
Topic: __eabi div operations
Replies: 13
Views: 10538

Re: __eabi div operations

I tend to agree with David on this one. If you are developing in the C/C++ context, whether with or without OS support, you'd expect the gcc libraries to work *out of the box* but in the context of my current bare metal project, which is a port of pure Intel assembler to ARM, you don't have that lux...
by tgritchie
Sat May 03, 2014 9:22 am
Forum: Bare metal, Assembly language
Topic: __eabi div operations
Replies: 13
Views: 10538

Re: __eabi div operations

In researching my pure assembler bare metal project I discovered this macro definition of a 32-bit integer division which could relatively easily be called from C code: @ Software simulation of 32 bit unsigned integer division @ Entry r0: numerator (lo) must be signed positive @ r6: denominator (den...
by tgritchie
Fri Apr 11, 2014 7:51 pm
Forum: Bare metal, Assembly language
Topic: Baremetal Forth?
Replies: 14
Views: 5042

Re: Baremetal Forth?

I would endorse the previous post regarding Roland's code. If you look at the quoted thread you will see some small contributions from me. Having studied this I am currently working on a port of Chuck Moore's colorforth. It is early days yet so I'd rather not post any code until I resolve some outst...
by tgritchie
Wed Aug 21, 2013 11:48 am
Forum: Bare metal, Assembly language
Topic: Debug on the raspberry pi for Baking pi
Replies: 3
Views: 1400

Re: Debug on the raspberry pi for Baking pi

Hello - I, too, experienced mechanical problems with my SD card from all those swappings in and out while developing my bare metal projects and have used the serial bootloader approach of David Welch. This method does, however, require some external hardware to interface to the COM port of your host...
by tgritchie
Sun Apr 07, 2013 9:20 pm
Forum: Bare metal, Assembly language
Topic: New Raspberry Pi bootloader (rpi-boot)
Replies: 46
Views: 11073

Re: New Raspberry Pi bootloader (rpi-boot)

Hello John - some more thoughts and queries below I've added some preliminary support for other functions to the protocol https://github.com/jncronin/rpi-boot/blob/master/raspbootin.c which support CRC checks of the sent information and the ability to browse directories on the server and download pa...
by tgritchie
Fri Apr 05, 2013 4:17 pm
Forum: Bare metal, Assembly language
Topic: New Raspberry Pi bootloader (rpi-boot)
Replies: 46
Views: 11073

Re: New Raspberry Pi bootloader (rpi-boot)

I understand the problems of the constant SD switching all too well - I have already snapped the corner off my Raspbian SD card with all the changes in making this bootloader (its now reasonably symmetrical). Don't I know it. Mine are heading the same way :( However, once I get USB working, my firs...
by tgritchie
Fri Apr 05, 2013 8:25 am
Forum: Bare metal, Assembly language
Topic: New Raspberry Pi bootloader (rpi-boot)
Replies: 46
Views: 11073

Re: New Raspberry Pi bootloader (rpi-boot)

I've been able to fix a CRC error experienced by one forum member by sorting out the SD clock rate (particularly by slowing it down for his old card) and the changes have now been uploaded. It may well fix CRC errors that other people are experiencing. Regards, John. Hello John - Like others I have...
by tgritchie
Wed Apr 03, 2013 7:32 pm
Forum: Bare metal, Assembly language
Topic: Raspbery Pi Forth Operating System
Replies: 31
Views: 20776

Re: Raspbery Pi Forth Operating System

A little googling reveals that the csud library is Alex Chadwick's USB code. Nonetheless I think it would be a good idea to commit this as a relocatable binary so that the Forth system can build *out of the box* as it were Trevor Yes csud is Alex Chadwick's USB code to access the keyboard. Alex get...
by tgritchie
Thu Mar 28, 2013 3:00 pm
Forum: Bare metal, Assembly language
Topic: Raspbery Pi Forth Operating System
Replies: 31
Views: 20776

Re: Raspbery Pi Forth Operating System

Hi Trevor, I used gedit (linux) for most my editing, but I have also used Eclipse. I recently went back to Eclipses, as an Editor, I like it. I have posted my Makefile on GitHub. .... Roland :mrgreen: Thanks for that. I note however that the makefile calls up a linker script called linker.ld - I th...
by tgritchie
Wed Mar 27, 2013 7:38 pm
Forum: Bare metal, Assembly language
Topic: Raspbery Pi Forth Operating System
Replies: 31
Views: 20776

Re: Raspbery Pi Forth Operating System

Hi Trevor, I used gedit (linux) for most my editing, but I have also used Eclipse. I recently went back to Eclipses, as an Editor, I like it. I have posted my Makefile on GitHub. .... Roland :mrgreen: Thanks for that. I note however that the makefile calls up a linker script called linker.ld - I th...
by tgritchie
Sat Mar 23, 2013 2:36 pm
Forum: Bare metal, Assembly language
Topic: Raspbery Pi Forth Operating System
Replies: 31
Views: 20776

Re: Raspbery Pi Forth Operating System

Hello Roland - I have been watching this thread for a while and recently downloaded your current source from github. I have been a Forth enthusiast for 30 years and have also used it professionally on occasion. Nowadays I am considering experimenting with bare metal Forths on the RPi and am very int...
by tgritchie
Sat Mar 09, 2013 2:49 pm
Forum: Bare metal, Assembly language
Topic: New Raspberry Pi bootloader (rpi-boot)
Replies: 46
Views: 11073

Re: New Raspberry Pi bootloader (rpi-boot)

Hello again - I just checked out revision 67 and there seems to be more consistency in the log data between power cycles and indeed some retries of CMD17 but I think it still fails to read the MBR :( Here is the log: fb_init, fb_addr: 0d385000 Successfully set up frame buffer Welcome to Rpi bootload...
by tgritchie
Fri Mar 08, 2013 1:00 pm
Forum: Bare metal, Assembly language
Topic: New Raspberry Pi bootloader (rpi-boot)
Replies: 46
Views: 11073

Re: New Raspberry Pi bootloader (rpi-boot)

OK - I'll look forward to it. I guess retries on CRC errors is a good thing though I should point out that this card may be a bit flaky in general as, although I have booted linux from it I have also noticed some mysterious quirks while doing so. Things like corrupt files, file system going read onl...
by tgritchie
Fri Mar 08, 2013 10:12 am
Forum: Bare metal, Assembly language
Topic: New Raspberry Pi bootloader (rpi-boot)
Replies: 46
Views: 11073

Re: New Raspberry Pi bootloader (rpi-boot)

Hello jnc100 - I checked out your bootloader, built it and tested it with few problems on a 4 GB Transcend SDCard. Many thanks for this contribution to the Raspi alternative OS effort. But I ran into some issues when I tried it on a Traveler 2GB card. It seems that on this card the code is having di...

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