Hardware issue on Zemmix Neo and related machines.

Hero (622)

29-03-2020, 20:08

Thank you for finding and solving this problem! Is it possible to submit the solution in this news post as well? As well as some more technical details about the problem and the solution?

Van KdL

Paragon (1450)

29-03-2020, 21:43

[ 2020.03.23 Hardware Patch ]

Hint for ZEMMIX NEO KR/BR, SX-1 and SM-X Machines.
How to fix the hardware issue of WAIT_n and INT_n.

Connections:
SLOT1 PIN-7 → 1Kohm → + 3.3V
SLOT1 PIN-8 → 1Kohm → + 3.3V

(Please do NOT connect PIN-5 to GND)

This patch solves the issue related to the pull-up resistors of the WAIT_n and INT_n signals inappropriately connected or absent. Changing the SLOT1 (or SLOT2) PIN 7 and 8 is therefore necessary to avoid cartridge malfunctions. The defective machines are Zemmix Neo BR / KR, SX-1, SM-X and all the PCBs attributable to this systems produced to date. The correct circuit was taken up by 1chipMSX. To detect the problem, measure the voltage of SLOT1 (or SLOT2) PIN-5. If it is equal to + 3.3 V, the hardware issue is confirmed and the modification must be carried out.

Van KdL

Paragon (1450)

29-03-2020, 21:45

SM-X audio output for sound cartridges

The first batch of SM-X does not sound from cartridges. So I implemented this mono connector which can be connected to an external mixer. Unfortunately this output cannot be mixed internally due to incorrect sizing of some components. Maybe it will be possible in the next batch.

Van msxtrd

Champion (271)

29-03-2020, 22:34

How does the problem exhibit on defective machines? Any particular soft / hardware cartridges are affected?

Van KdL

Paragon (1450)

29-03-2020, 23:21

Mr. Hara explained to me that cartridges that use these signals could introduce too much current into the FPGA due to the absence of resistors. So there is the risk of damaging the machine permanently or in the most optimistic hypothesis of creating unnecessary overheating.
Finally, some cartridges may not be compatible such as Pazos cartridges that stop the system on boot.

Van OeiOeiVogeltje

Paragon (1426)

29-03-2020, 23:31

KdL wrote:

SM-X audio output for sound cartridges

The first batch of SM-X does not sound from cartridges. So I implemented this mono connector which can be connected to an external mixer. Unfortunately this output cannot be mixed internally due to incorrect sizing of some components. Maybe it will be possible in the next batch.

wut?
what does that mean?

Van OeiOeiVogeltje

Paragon (1426)

30-03-2020, 01:07

well, here was me thinking i had a "first batch" SM-X (it says #3)
but there are SMD resistors in place there

Van KdL

Paragon (1450)

30-03-2020, 01:43

OeiOeiVogeltje wrote:

well, here was me thinking i had a "first batch" SM-X (it says #3)
but there are SMD resistors in place there

Victor had already explained to me that some SM-X have been modified with respect to n. 1. So if the contact points don't match, you have to look for the three capacitors that come out of the PIN-49 of each slot and connect to the output of one of them.

Unfortunately, not all cartridges are sounding right and I think the 2.2uF capacitors are the cause. In fact, according to the 1chipMSX scheme, they should be 4.7uF but currently I have no capacitors of that size in the house, so I still cannot confirm the improvement.

Van tfh

Prophet (3280)

30-03-2020, 09:55

I guess this is only an issue if you use real cartridges in your Zemmix Neo. As I don't own any of those, I guess I don't have to worry. But who knows... maybe in the future?
Well, that might be a good reason to plan a visit @ OmegaMSX/Alucard when this Corona issue is over

Van raymond

Hero (622)

30-03-2020, 19:07

KdL wrote:

[ 2020.03.23 Hardware Patch ]

Hint for ZEMMIX NEO KR/BR, SX-1 and SM-X Machines.
How to fix the hardware issue of WAIT_n and INT_n.

Connections:
SLOT1 PIN-7 → 1Kohm → + 3.3V
SLOT1 PIN-8 → 1Kohm → + 3.3V

(Please do NOT connect PIN-5 to GND)

This patch solves the issue related to the pull-up resistors of the WAIT_n and INT_n signals inappropriately connected or absent. Changing the SLOT1 (or SLOT2) PIN 7 and 8 is therefore necessary to avoid cartridge malfunctions. The defective machines are Zemmix Neo BR / KR, SX-1, SM-X and all the PCBs attributable to this systems produced to date. The correct circuit was taken up by 1chipMSX. To detect the problem, measure the voltage of SLOT1 (or SLOT2) PIN-5. If it is equal to + 3.3 V, the hardware issue is confirmed and the modification must be carried out.

Ok, so there are no tracks that have to be cut and only two resistors that have to be placed. That should not be so hard to do :)

Van KdL

Paragon (1450)

30-03-2020, 21:15

raymond wrote:

Ok, so there are no tracks that have to be cut and only two resistors that have to be placed. That should not be so hard to do

Yes, the changes are very simple.

I turn to pcb manufacturers. All the defects we are experiencing (including the Zemmix Neo audio interference problems) can be solved simply by applying the 1chipMSX schemes published in 2006 together with the device. The following is the configuration of the slots as an example.

Van АIеks

Paladin (949)

31-03-2020, 15:04

This is all weird. It is necessary to consider the features of FPGA. These signals are the TTL open collector (/INT, /WAIT).

I wonder what cartridges give these signals : -?

Van KdL

Paragon (1450)

31-03-2020, 17:03

АIеks wrote:

This is all weird. It is necessary to consider the features of FPGA. These signals are the TTL open collector (/INT, /WAIT).

I wonder what cartridges give these signals : -?

These contacts remain open only until a cartridge is inserted and in the case of INT_n until they are used by some internal signals. The question is not how many cartridges use them, but simply, why do you want to leave an incorrect design? Maybe you prefer to insert cartridges waiting to meet the one that will damage your device?

Van raymond

Hero (622)

31-03-2020, 17:26

KdL wrote:

raymond wrote:

Ok, so there are no tracks that have to be cut and only two resistors that have to be placed. That should not be so hard to do

Yes, the changes are very simple.

I turn to pcb manufacturers. All the defects we are experiencing (including the Zemmix Neo audio interference problems) can be solved simply by applying the 1chipMSX schemes published in 2006 together with the device. The following is the configuration of the slots as an example.

Sorry for the many questions :) Are the lines 15 and 16 also wrong then?

And furthermore, can you tell me more about: "I spent many days discussing with Carmeloco some problems related to the cartridges connected on Zemmix Neo machines."? What kind of problems did you encounter?

Van KdL

Paragon (1450)

31-03-2020, 18:45

The 1chipMSX scheme is the correct one and the pull-up resistors should all be 1Kohm. Changing the pins 15 and 16 does not entail any real utility since PIN-15 is only an OUTPUT contact and an oversized 10Kohm pull-up does not interfere in any way on the reading by the cartridges. PIN-16 is simply unused and unnecessary. I therefore preferred to simplify the hardware patch by correcting the INPUT pins where the pull-up is totally absent (or incorrect like the SM-X).

I would also like to clarify that if we wanted to complicate our lives, pins 5 and 6 should be detached from the 10Kohm pull-ups present on the Zemmix Neo. However, this change is not necessary. In fact, these pins cannot interfere with the operation of the slot because PIN-5 is not used while PIN-6 is an OUTPUT pin that is never opened by the firmware.

I inform you that the problem found on Pazos cartridges (Who Dares Win MSX2, the Goonies 'r' good enough, etc.) is a high impedance on the WAIT_n pin which pauses the machine. The absence of the pull-up resistor prevents the reading of a value "1" on that pin necessary to deactivate the waiting state.

The WAIT_n signal has been correctly activated only by the OCM-PLD v3.8 firmware and this problem is not visible in the previous firmware because they do not read the pin-5 correctly. So only thanks to the OCM-PLD v3.8 firmware we have been able to discover the hardware issue of Zemmix Neo and related machines. The WAIT_n signal correction was created by Victor Trucco.

I hope I have clarified your doubts.

Here the MSX Cartridge slot on MSX Wiki.

Van raymond

Hero (622)

03-04-2020, 14:51

I have made the changes as described by you. It is still working OK

Van KdL

Paragon (1450)

03-04-2020, 19:54

raymond wrote:

I have made the changes as described by you. It is still working OK

Excellent but I'm not the one saying it, but the 1chipMSX scheme.

Van KdL

Paragon (1450)

06-04-2020, 19:34

[ Update 2020.04.06 of the Hardware Patch ]

Today Carmeloco has detected a rare situation that requires the correction of the pull-up resistance of pin 15 (RESET) in the slot of Zemmix Neo and SM-X (not necessary on SX-1).
The combined games "Head over Heels" and "Batman MSX2" cannot trigger tricks without this correction because the reading of the pin-5 does not take place correctly.

Therefore I recommend to correct the resistors of pin-15 and pin-16 to those who want a complete patch by applying 1Kohm instead of 10Kohm as indicated in the 1chipMSX scheme.

Van hardwaremaker

Master (245)

06-04-2020, 23:40

I made the new modification, but only in WAIT, INT and RESET. I think that the resistor in the pin 16 is not necessary, because this pin is not in use in the MSX machines. In fact, in the real MSX machines, this pin is not connected.

Van KdL

Paragon (1450)

07-04-2020, 00:31

hardwaremaker wrote:

I made the new modification, but only in WAIT, INT and RESET. I think that the resistor in the pin 16 is not necessary, because this pin is not in use in the MSX machines. In fact, in the real MSX machines, this pin is not connected.

Pin-16 is connected internally to the FPGA and I recommend using the 1Kohm pull-up resistor anyway. On the other hand, pin-5 and 6 do not have a pull-up resistor and if you have issues with some cartridges it would be useful to remove the 10Kohm resistor on them.

Van KdL

Paragon (1450)

08-04-2020, 00:45

I would like to clarify to all Zemmix Neo users that the fastest way to run this hardware patch on their device, is to remove the resistor array R16 (4x 10K ohms) and then reconnect pins 7, 8, 15 and 16 (from slot- 1 or slot-2) with four single 1K ohm resistors up to a voltage point of +3.3V. Whatever the way you do it, you have to recreate the same connections used by 1chipMSX.

Van KdL

Paragon (1450)

08-04-2020, 05:22

Note: The hardware patch of SX-1 requires no further modification.

Van OeiOeiVogeltje

Paragon (1426)

08-04-2020, 17:41

im getting a bit confused here
i mailed victor trucco for this about this patch and he said my SM-X has no problems

my SM-X had these two resistors already on (except they are 103 instead of your 102)

Van KdL

Paragon (1450)

09-04-2020, 04:24

The problem affects all machines in general because 10k pull-up resistors do not work properly on some cartridges. I have personally tested the Kralizec Goonies cartridge that does not start if 10k pull-ups are used. Therefore if the cartridges are blocking the SM-X on startup, you need to replace these resistors as I have described.

Victor told me that he had no way of testing the external cartridges and therefore has no idea if 10k pull-ups are working well. SM-X was sent to me by Victor to modify its firmware and test the hardware, so I'm just doing my best to satisfy his request. Consider that 1chipMSX is the only machine without this issue and that SM-X took its cue from the faulty scheme of Zemmix Neo.

Van OeiOeiVogeltje

Paragon (1426)

09-04-2020, 08:57

Aha that makes thing clear
What other cartridges are affected?
so i can test it myself

Van KdL

Paragon (1450)

09-04-2020, 16:34

OeiOeiVogeltje wrote:

Aha that makes thing clear
What other cartridges are affected?
so i can test it myself

I don't have a precise list of cartridges to report, but the problem is due to the wrong pull-ups and not to the cartridges. Some test cartridges are made by Pazos and work correctly on every real MSX and on 1chipMSX only. As I said in a previous post, the tests must be performed with the OCM-PLD v3.8 firmware which is the only firmware capable of managing the external WAIT_n and INT_n signals.

Therefore you can ask Carmeloco to send you a short list of cartridges that don't work using 10k pull-ups or you can simply apply the hardware patch and fix the issue once and for all.

Van raymond

Hero (622)

09-04-2020, 20:37

Hmm, I have to order some SMD resistors then, as I only have the larger versions... I do not have a lot of experience in soldering those SMD resistors, so this is going to be a challenge...

Van OeiOeiVogeltje

Paragon (1426)

09-04-2020, 23:08

easy ..even idiot me did it

Van Yobi

Master (149)

10-04-2020, 22:24

Without the update I had so much problems with the GFX9000 in my Zemmix Neo.
But after fixing like KdL suggested it runs great.
Bye bye problems. Even at 10MHz.

Van KdL

Paragon (1450)

13-04-2020, 21:39

Van Wolverine_nl

Paragon (1160)

14-04-2020, 13:42

I wonder if newly sold machines are treated with the fix? Does anybody know?

Van KdL

Paragon (1450)

14-04-2020, 20:36

Some infos on "SM-X audio output for sound cartridges".

Unfortunately, the internal impedance of SM-X audio output cannot be regulated by the firmware as it happens on 1chipMSX and Zemmix Neo. This I have chosen is only a quick solution, particularly suitable if you connect one audio cartridge at a time. If you want to use two or more sound cartridges, it would be best to separate all three slot outputs and connect them to the mixer one by one separately and not all together as now.

Van syn

Prophet (2113)

15-04-2020, 00:45

Does the SX-1 Mini have these problems as well?

Van syn

Prophet (2113)

15-04-2020, 00:46

Wolverine_nl wrote:

I wonder if newly sold machines are treated with the fix? Does anybody know?

I want to ask them later on. You interested in buying one of those devices from 8bits4ever?

Van Wolverine_nl

Paragon (1160)

15-04-2020, 09:50

Eventually yes.

Van KdL

Paragon (1450)

15-04-2020, 19:16

syn wrote:

Does the SX-1 Mini have these problems as well?

I suppose so. I advise you to check if pins 7 and 8 are connected to an array
of 1k resistors (code 102) and if not, it means that the modification is necessary.

Van syn

Prophet (2113)

15-04-2020, 19:27

I dont have a mini im interesed in buying one

Van KdL

Paragon (1450)

16-04-2020, 11:50

If it was produced before this month then it is defective. However, ask the author for confirmation.

Van ssfony

Expert (83)

01-06-2021, 21:34

So, fixing the SX-1 is just soldering two wires? I can't see exactly how it was done on the photo. Does anyone have a better close up?

Hardware issue on Zemmix Neo and related machines.

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