Problem with 2nd LCD

MIDIbox SEQ
1

I’ve built my Version 4 Seq, but have a problem with the 2nd LCD module. No matter what I do it always just displays a top row of 20 black boxes and nothing else.

I have swapped it for the 1st LCD and it is still the same. I have also tried another LCD module with the same effect. The MidiSeq seems to be functioning ok otherwise.

I figure it is something to do with enablement of the LCD, but as I have tried swapping it to the other junction (15A/15B) and it makes no change to the display I am a bit puzzled as to what is happening here.

I can get both LCD screen displays by swapping the “good LCD” between Junction 15A/15B ok.

I’ve read through the construction of the STM32 core construction where it says the 2nd LCD is not initialized by default. I have just uploaded (via USB and Uart Midi) the latest Beta 22 of MidiSeq V4 with no change to LCD after reboot. I have also read the Wiki info about the LCD problem with the black bars but as I have uploaded a correct application is does not seem to apply.

Anybody come across this at all ?

Thanks in advance for replies.

2

Hi SynGy7,

to me it is not really clear what you described:

* Do you gett all your LCDs working by connecting them to J15A,

and none of them works at J15B ?? -> Then I would check all soldeing Joints and traces on J15B,

also check if your DIL connector has propper contact. You could connect your LCD to J15B and then

ping the connection to the solder pads on the display to the connector pins on J15A, only the enable line

you have to ping to a solder pad on the PCB. This way you would also find a faulty connection on the LCD Side.

* Or do you have one LCD that does neither work on J15A or J15B -> bad solder joint or DIL connector on the LCD side, or broken LCD?

Good luck, and best Regards,

Gridracer

3

Thanks for the reply. Sorry about not being clear…

I have one LCD which works in both junctions 15A and 15B. The other LCD only shows the black boxes across the top row as if it is not being initialized, it shows these black boxes when connected in 15A or 15B (used different ribbon cables to test as well with no change).

This morning I received a brand new LCD and it does exactly the same thing. I find it hard to believe that a brand new LCD exhibits the exact same fault as the previous one. I must be missing some crucial setup problem or something.

I am a bit lost as to what is happening here.

Going away for some days holiday so unable to reply until late next week, but any help appreciated. :smile:

4

did you check cable ? is E line of core connected to E line of the LCD (test with your multimeter in “bipbip” mode)

check contrast too (turn 10k pot all his range)

cheers

5

I have checked all I can on this…Grr

Yesterday I got both LCD’s working all day, today the 2nd one is not initializing again. Nothing has changed in setup etc.

Does anyone have a reliable source for the LCD’s (originally got 2 LCD’s from the German supplier (Mike ?), one of which will not initialize. Bought a new LCD on Ebay which works now and again).

I would prefer to get the LCD’s in UK (definitely not from the US as the customs charge is a lot).

Again, appreciate the replies.

6

Checked over the core once again. Buzzed out all the connections to the LCD’s from the core and 595 chip etc - all ok. Shortened ribbon cables to approx 150mm each. Tried power on several times and suddenly the second LCD started. If I disconnect power I know it will not come on again.

Can somebody enlighten me as to how the 2nd LCD is initialized. I assume it is detected somehow by the STM 32 CPU chip and initialized via the boot program from ROM. I am wondering if there may be some fault with my STM 32 chip (it checks out ok when queried via MIOS Studio though).

This is very puzzling…any help appreciated.

Thanks

Dunc

7

Can you confirm that one LCD works at J15A and J15B, and that it outputs different screens?

(left/right side of the MBSEQ screen)

In this case the hardware (core) is working correctly, and the application is properly installed as well.

Initialisation is done here: http://svnmios.midibox.org/filedetails.php?repname=svn.mios32&path=%2Ftrunk%2Fmodules%2Fapp_lcd%2Fclcd%2Fapp_lcd.c

Only the MBSEQ application will initialize mios32_lcd_device == 1 (all others only mios32_lcd_device == 0).

As you can see in the source code, each device has a dedicated timeout flag - if MIOS32 doesn’t get a response from a display after 2500 (!) tries, it won’t be accessed anymore.

The same mechanism have been used by the PIC based MBSEQ V2 and V3 firmwares since years, this is well tested code.

Best Regards, Thorsten.

8

Thanks for info TK.

The "good " LCD works in either of J15A/B and shows each screen. I didn’t doubt the code, but wondered if the core hardware was a bit erratic. Your test proves it to be ok.

I must be just “lucky” in getting 2 broken LCD’s.

I guess I have to buy yet another LCD then…

Thanks

9

Hi there,

just wanted to report another possible cause for blocks displayed on the LCDs, which happend in my case:

Upper row on both displays showed solid blocks and whilst I suspected the Pinning/cables to be wrong,

it turned out that R2 resistior array was stuffed upside down :baby: .

Since everything went fine during the building/testing-stages this didn`t come to my multimeter-mind so I rather went on going tilt by making numerous cable-versions and blowing backlights of a regular LCD and also of an optrex :bye:

Now the seq ist running fine.

apart from.. well ..spare Optrex anyone..? :whistle: