ePaper Display (28084)
RobR
Posts: 15
in Accessories
I'm enjoying playing with this display wired to a FLIP; have displayed large fonts, different orientations, random numbers, programs running from EEPROM.
However, I may have already partly damaged it. When the display toggles from "white paper" to black, there are multiple vertical white lines in the black.
The Product ID 28084 Details Key Specifications page says "Operating voltage: 3.3V/5V".
I took this to mean the display would operate on either 3.3 volts or 5 volts. But when connected to the FLIP USB5V pin, nothing on the display at all. Does not do the black / white / black / white routine when powered up to get rid of ghosting. My multimeter shows this pin to have 5 volts. Then when hooked back to the FLIP 3.3 volt pin, it works.
The Waveshare Specifications page 17 Maximum Ratings says: "Logic supply voltage -0.5 to +4.0 volts." This makes me think the device should be connected only to 3.3 volts.
However, I may have already partly damaged it. When the display toggles from "white paper" to black, there are multiple vertical white lines in the black.
The Product ID 28084 Details Key Specifications page says "Operating voltage: 3.3V/5V".
I took this to mean the display would operate on either 3.3 volts or 5 volts. But when connected to the FLIP USB5V pin, nothing on the display at all. Does not do the black / white / black / white routine when powered up to get rid of ghosting. My multimeter shows this pin to have 5 volts. Then when hooked back to the FLIP 3.3 volt pin, it works.
The Waveshare Specifications page 17 Maximum Ratings says: "Logic supply voltage -0.5 to +4.0 volts." This makes me think the device should be connected only to 3.3 volts.
Comments
The weird thing is, all examples given by Waveshare (Pi, Arduino, STM32) say to hook the module up to 3.3 volts.
It might be that the module has a chip on it to convert incoming 5 volts to 3.3 for the ePaper "raw panel" as they call it but I cannot tell since the chip looks proprietary.
I tried again using the USB 5V FLIP pin and still nothing. Then tried 5 volts from my Rigol (gnd to FLIP gnd, 5v to ePaper Vcc). It worked for a short time and then stopped. Before it stopped it displayed a thick white band about 2/3 down the display against the black, like it could not be refreshed correctly.
After which it would not work on the FLIP 3.3V. After disconnecting and letting it sit for 5 minutes, it now again works from the FLIP 3.3V.
Perhaps I need to rewire on a different breadboard with different wires to see if there is some sort of intermittent. Or perhaps this specific module really does not like having 5 volts applied ???
Mike
The schematic for the ePaper module is posted here: https://www.waveshare.com/w/upload/8/85/2.9inch_e-Paper_Schematic.pdf. It uses a TXS0108E level converter, which has a set of 'A' pins for the lower-voltage device and a set of 'B' pins for the higher-voltage device. The 'B' pins are connected to the external I/O and have an absolute maximum voltage rated at 6.5 volts, regardless of Vccb. They do have a recommended high input voltage of Vccb, but signals exceeding Vccb, while still under 6.5 volts, should not cause any damage, although it could cause undesired operation.
So, it doesn't seem that 5V input is a problem. This is a Waveshare-supplied product, as you noted.
I'd be happy to replace it for you. Contact me offline for an RMA kgracey@parallax.com
[update: according to Michael your display is working, so disregard this message. But, if anybody ever needs service from us just say something. I don't often monitor the forums so feel free to draw my attention to possible RMA issues quickly via email kgracey@parallax.com]
Thanks,
Ken Gracey
I will investigate this more. But thanks to all.
I agree with you, I think the issue is with commands I'm sending to the display and there is nothing wrong with the display.
I haven't been able to change the size of the font - do you have any hints you can share?
Thanks,
Tom
I only need 4 cogs for the job.
:clown:
You need to email sales@parallax.com
or
support@parallax.com
for am RMA.
I just got the joke.
You really cut that one down? Not Photoshop?
I almost killed one of my precious Parallax P1 Protoboard without USB by just drilling a mounting hole right thru the somewhere hidden reset connecting PCB part, naturally AFTER I populated the complete board, you know, come on Mike just one more screw and it will be more robust and look better. Yeah.
Took me days to find out and fix that by carefully cleaning the new created via from reset to ground and rewire the reset button.
I did, on the other hand, cut out the USB part of new Protoboards successful to regain P31/30 and another PropPlug…
Mike
To save the whole board, I take a Dremel and cut the flip away.
I don't want to stress the main pcb.
After soldering a new Flip it runs fine again.
I saved a board of 200$ by cutting a Flip.
So no Photoshop.
Someone here DID Dremel'd off a P1 DIP, cutting thru plastic, not destroying the internal chip. And had it still running.
Mike
It is like burning an EEPROM where you write to the display once and then shut everything down. Even power and the display stays the way you burned it.
I wrote my own driver for this display and found the information very confusing and not very friendly. The only reason you need a controller on this display is for the burning process that requires some strange voltages to update the display pixels.
Mike
I see bits of copper