Issue with SDCard Emu Rev B + Mod on A500

[bobobear]

Hello!

I have just installed a Rev. B SDCard Floppy Emulator with SRAM added as described in the Docs in an A500. The board is jumperes DF0 only on ID0 and running Firmware 1.8.2.40. When loading the FEManager from SD (Ver. 1.8a), I get the on screen error

"LBA Change Test Failed ! Write Issue ?"

and an LCD readout of

"Direct Access"
"LBA:00000000WESE".

Also, the red and green LEDs are on.

I have swapped in a Rev. C board from another machine for testing, and this does not produce the error with the same SDCard. Jumpers are the same on that board. The SDCard is new, freshly formatted and only contains the cfg and the autoboot.hfe from the FEManader ZIP fild for Amiga DF0.

Do I need to get another Rev C board or could there be something wrong with the SRAM Mod that may lead to this error?

I'd be very grateful for a helpful response.

Thanks!

[Jeff]

Hello!

I have just installed a Rev. B SDCard Floppy Emulator with SRAM added as described in the Docs in an A500. The board is jumperes DF0 only on ID0 and running Firmware 1.8.2.40. When loading the FEManager from SD (Ver. 1.8a), I get the on screen error

"LBA Change Test Failed ! Write Issue ?"

you just failed the hardware modification... look at the lcd at power up, the emulator should say something to you...

[bobobear]

you just failed the hardware modification... look at the lcd at power up, the emulator should say something to you...

Hmmm... Nope. Without an SDCard the FW version is displayed for about half a second, then it switches directly to "No SD/SDHC Card found!". With the SDCard I get the FW version and immediately after that, loading of AUTOBOOT..HFE starts. No error messages at all.

Is there any way to test the Mod other than tracing all the wires (which I did right after making all the solders and everything seemed right).

Thanks again!

[bobobear]

OK, I now had time to trace the wirings in my SRAM mod in search of the error. Things still look fine:

* there are no shorted pins on the SRAM (except 7 and 8, which are both 3.3V) and the solders on the PIC have also not created any cross connections
* Measuring at pins 1 (SRAM) and 22 (PIC), 2 (SRAM) and 29 (PIC), 5 (SRAM) and 27 (PIC), 6 (SRAM) and 28 (PIC) I get between 218 and 221 Ohms, so these should also be alright.
* Measuring at pin 4 (SRAM) and common GND (Black) at the power connector, I get 0 Ohms, so the connection is fine.
* Pins 8 and 7 (SRAM) are both connected to the middle pin of the regulator, which should be Vout 3.3V
* I put a 100 nF ceramic capacitor at pin 8, the other end of it is connected to pin 4 (GND), to even out the voltage

To me, this means that there can be three possible problems:

1. The SRAM Chip is faulty. Is there any way to test for that?
2. The capacitor is faulty. Should I not have used a ceramic capacitor?
3. The resistors have too much tolerance. I used "gold band" carbon resistors, so the tolerance is +/- 5%. Should I have used more precise metal resistors? 2% or 1%?

I'd be very grateful for any helpful ideas.

Thanks a lot!

[Jeff]

1. The SRAM Chip is faulty. Is there any way to test for that?

Try another one...

2. The capacitor is faulty. Should I not have used a ceramic capacitor?

No this is not this...

3. The resistors have too much tolerance. I used "gold band" carbon resistors, so the tolerance is +/- 5%. Should I have used more precise metal resistors? 2% or 1%?

No this is not this...

Have you checked the 5V voltage ?

[bobobear]

Hello again!

Now, I finally have found the time to play with the Floppy Emu again. And the problem persists. Here's what I've done since your last reply:

* rebuilt the mod from scratch using all new parts (resistors, capacitor and SRAM) on a fresh piece of epoxy
* redid the wiring to the PIC, V+ and GND
* measured impedance between the four pins on the PIC and the corresponding ones on the SRAM socket (217 Ohms each) before inserting the new chip
* checked all pins for short circuits or cross connections
* measured the 3.3V on the SRAM and the 5V on the PIC, both well within specs of the two chips
* compared the wiring with the datasheets of the SRAM and the PIC, just to be safe
* traced an measured the conections to the SRAM on a Rev. C board to make sure they match --> all is fine

This leaves me with the one final possibility that the PIC itself is damaged, possibly because it got overheated when soldering the wires to the pins (the other possibility being of course that I am completely unable to properly use a multimeter).

What do you think? Does it make sense to try and switch the PIC? And where would I get a programmed one?

Warmest greetings,

BB

[Jeff]

Please give me the exact values about the voltages !

[bobobear]

Finally had time to measure the voltages:

* 3.26 V at Pins 7 & 8 of 23K256
* 4.94 V at Pins 11 & 32 of PIC18F4620

The same voltages measured at the output of the regulator and the 5V branch of the power connector, respectively.

Greetings,
bobobear

[bobobear]

Hello again,

have you had a chance to think about my issue again? IMHO the voltages measured seem fine. Should I go for replacing the PIC chip on the Emu Board?

Thanks and warmest greetings,

BB

[Jeff]

No idea at all since i don't have the board in my hand... I suppose that you don't have any oscilloscope ?

[bobobear]

Unfortunately I don't. However, i can get access to a proper PICkit3 setup, so i am considering getting a new PIC, reading out the flash memory of the one on the Rev.C Emu board I have, writing that to the new PIC and then swapping that for the one on the Rev.B board I am having trouble with.

Do you think that this is worth a try?

Thanks and greetings,
BB

[TTD]

Hello!

I have just installed a Rev. B SDCard Floppy Emulator with SRAM added as described in the Docs in an A500. The board is jumperes DF0 only on ID0 and running Firmware 1.8.2.40. When loading the FEManager from SD (Ver. 1.8a), I get the on screen error

"LBA Change Test Failed ! Write Issue ?"

and an LCD readout of

"Direct Access"
"LBA:00000000WESE".

Also, the red and green LEDs are on.

I have swapped in a Rev. C board from another machine for testing, and this does not produce the error with the same SDCard. Jumpers are the same on that board. The SDCard is new, freshly formatted and only contains the cfg and the autoboot.hfe from the FEManader ZIP fild for Amiga DF0.

Do I need to get another Rev C board or could there be something wrong with the SRAM Mod that may lead to this error?

I'd be very grateful for a helpful response.

Thanks!

Well I can see this is an old post.
I have the same issues with my a500 running kickstart 1.2 on rev 6a a500 motherboard with only 512k memory.
I have reflash firmware to version 1.7.2.0 if I update it to the same version as you I get in display lba with the letters but it also tells me SRAM error. I dont know if this causes old rev.b mod or to high firmware incompatible.
I have try 2 SRAMs same problem.

[Jeff]

Well I can see this is an old post.
I have the same issues with my a500 running kickstart 1.2 on rev 6a a500 motherboard with only 512k memory.
I have reflash firmware to version 1.7.2.0 if I update it to the same version as you I get in display lba with the letters but it also tells me SRAM error. I dont know if this causes old rev.b mod or to high firmware incompatible.
I have try 2 SRAMs same problem.

There is just something wrong with your mod or with the chip that you are trying to use.

[TTD]

Hi Jeff
Thanks for reply.

If the mod is wrong it could be, but then where have i made the error.
The SRAM works fine with firmware 1.7.2.0 i can write on the amiga if I upgrade to latest firmware I get sram error and the lba with letters, is it because rework of how it control the ic pic18f4620.
So what I can say is a sram ok on firmware lower than 1.8 if 1.8 or higher it tells me sram fail, I dont know if any 1.8 at all will work.

Is there an archive about old firmware I could try more out.

The SRAM is in my mod on a small test PCB with a 8 pin socket and 8 pin sram insert.
I dont know if is the old 40 pin ic there is main on the old rev.b pic18f4620 has something more different than other in usb and which firmware did rev c came out with original?
SRAM chip used is 8 pin dip 23k256. microchip.
Is it because I have old browser for amiga which on screen tells me 1.6b, is that some beta?

[Jeff]

With the mod you can use the very last firmware version on the rev B.

If this one show you an "sram error" message at power up, this mean that there is something wrong with the sram add-on (bad solder...).