Display frustration #1019
-
Beta Was this translation helpful? Give feedback.
Replies: 6 comments 3 replies
-
|
One other detail: if, on garbled display as above, I pull the cable from the display with the Pi still running, the plug it back in, the display is clear and accurate, but displays only one line. For instance, if I've already clicked and rotated through to performance/load, I had see the bank and patch number of each performance setting. If I did this immediately after boot, the display reads "Minidexed", with no second line. Are there further settings for I2C displays that could be added to the .ini file? |
Beta Was this translation helpful? Give feedback.
-
|
One additional point, which may relate to this thread: (note that we are both running on Zero 2W.) |
Beta Was this translation helpful? Give feedback.
-
|
I am the the person that started the thread you linked to. Fortunately my experiences are a bit more predictable so I have been able to work around the issue. I am pretty sure there is some sort of race condition occurring and/or certain MIDI traffic causes too much latency that causes issues with some displays. The lower performance of the pi zero 2w is possibly a contributing factor. I suspect changing the boot order to ensure the USB gadget is initialized AFTER the display would likely fix the boot issue. Here are some additional observations that may help to get to the bottom of it.
The concerning thing with your setup is that you still observe issues while connected to a power supply. Just spitballing here... I suspect for the display to become corrupted, it has to receive the corrupted data. In order to do that, it would have to respond to its i2c address so the first byte of the transfer should be good. Since most/all the characters look bad I wonder if the corruption occurs before the buffer is sent as I find it unlikely only the address byte would be correct. If you have a scope and can capture the i2c traffic when the display is working and not working, you might be able to confirm if bad data is being sent to the display. |
Beta Was this translation helpful? Give feedback.
-
|
Thanks, @sgreasby. I ordered 2 more displays with one day shipping, determined to figure this out. I read elsewhere (but I can't find where) that these displays can fail to sync to the right clock speed, hence my question about whether other LCDI2C= variables could be added? |
Beta Was this translation helpful? Give feedback.
-
|
@craigyjp, I haven't, and unfortunately I don't have a piggy back on hand. However, I think I may have just found (part of?) the problem: the data pins are feeding back 5v to the PI rather than 3.3V. There are a few tiny jumpers beside the i2c port, but I'm going to need to do some digging to see if any of them affect outgoing voltage or level-shifting. Turns out I have a pile of "i2c" displays that are not, in fact, i2c displays. |
Beta Was this translation helpful? Give feedback.
-
|
@craigyjp, you were correct. I picked up a new display with backpack this morning, and everything runs just fine. I'm a little surprised major companies are selling non-standard products, but I suppose these things are driven by cost in the end. Now to find a better case. |
Beta Was this translation helpful? Give feedback.



@craigyjp, you were correct. I picked up a new display with backpack this morning, and everything runs just fine. I'm a little surprised major companies are selling non-standard products, but I suppose these things are driven by cost in the end. Now to find a better case.