I have 1 9486 3.5" SPI TFT connected (well, about to be connected) to an ESP WROOM32, and have a couple of questions.
There are tutorials showing a similiar display connected to a Uno directly powered by its 3V3 pin. Is this actually OK to do with an ESP32?
The other question is how to to turn off the display for battery use. I'm using the TFT_eSPI library. The LCD has an EN pin which from what I've read will cut the 3V3 power, but I've read dire warnings of supplying control voltage to a display that's not powered up.
I've also read that just putting the ESP to sleep will also power off the display.
Post a link to the actual ILI9486 display that you have bought.
You can send the controller to sleep but this only saves a few mA.
Switching the backlight LEDs off (100mA) depends on the particular display hardware.
Thanks David. Yes, I see now a board with any given controller could be very different, sorry for the lack of info. The photos on that page are actually pretty bad; this is a closup of what I have, including the xpt2045 touch controller.
Are there any other power saving to be had than dimming the BL?
I recently bought a 320480 3.5 inch SPI TFT 14-pin to wire it to an ESP32WROOM32. I got it via AliExpress. This is the link. However the seller claims that the controller is n ILI9488.
Wiring is as follows (picture is for a 320240 where pinout is identical); the library to get things working is TFT_eSPI by Bodmer.
Many, many thanks to you photoncatcher and to david prentice for such patience and tremendously useful information, indeed a flying start to a project I was a little wary of. I do have another issue, not so much how to save power but how to power these in the first place. I am rewasonably confident with this but emboldened by this groups helpfulness I'll put this piece of the power puzzel out:
I'm finding that the WROOM won't supply enough current by itself. The dsiplay control logic and BL at full brightness draw 175mA at 5VDC, it's a bit much to expect it to be able to.
How then do I power this? I've read that of the 5V in on he WROOM, the USB port and the 3V3 that only one should be active at once; will the logical step of powering both the display and the WROOM from the same 5V (or 3v3) regulator making sure they have common grounds work OK? I notice too that on this board the 3V pin is labelled in; I've only ever powered it via USB so far and am not sure the 3V3 pin is even used as an input.
My apologies for what are banal questions. I had a moment earlier on when I thought I'd destroyed the display somehow as it didn't light its BL from the ESP32 3V3 power. Yeah it wouldnt have done so properly anyway, but in practice I've found it does light at 3V even withouth the solder bridge. I should probab;y not have done that, it no longer lights from the board, and I've used an external PSU. My real issue that being in Australia, these inexpensive components are not that inexpensive - the ESP and diplay together cost over $50 and I'm just being really cautious. The only real issue seems to be with programming, requiring some cable reconnects.
It's also demoloshing my idea of having this battery powered; I can power off the WiFi most of the time, and blank the BL but even so it's thirsty.
That diagram matches my change in the TFT_eSPI libraray I think #define TFT_MISO 19 #define TFT_MOSI 23 #define TFT_SCLK 18 #define TFT_CS 15 // Chip select control pin #define TFT_DC 2 // Data Command control pin #define TFT_RST 4 // Reset pin (could connect to RST pin)
//#define TFT_RST -1 // Set TFT_RST to -1 if display RESET is connected to ESP32 board RST
and am hoping that's all that needs changing.
It should be more widely recognised that people in these forums share their knowledge so professionally, It is appreciated.
175mA sounds quite reasonable. i.e. ILI9486=25mA, backlight=150mA.
The 3.3V regulator U1 on the Red display pcb will cope with 175mA from display_VCC=5V (i.e. from USB)
The 3.3V regulator on the WROOM-32 pcb will cope with 175mA if you want to bypass the U1 display regulator (i.e. short J1)
Just compare the size of U1 with the WROOM-32 regulator (bottom left of pcb) in #6. An extra 175mA is ok.
Personally I would use the display regulator. USB can provide the current. No point in burdening the WROOM-32 regulator.
If you switch the backlight off you reduce by 150mA
If you sleep or power-off the ILI9486 you reduce by 20-25mA
Be realistic. The ESP32 takes a lot of current with WiFi + TFT + backlight + USB-UART.
It is complex to sleep every component.
So sorry just to clarify again, run both the WROOM and the diplay off Ithe same USB port, and let their respective regulators do the work when running?
Man this is frustrating. OK I know the diagram photoncatcher sent is of an ILI9341 (or 9488...) and I've been talking about the 9486. I have the wiring checked 3 times, and get the same error on 2 diffewrent WROOM32 boards.
' A fatal error occurred. Timed out waiting for a packet header'
There is also a mention of 'not being able to automatically detetmine the flash sise, assuming 4M'. I can flash the board fine if nothing is attached to it. Attach the display and I get the error.
Sorry I know this is now off topic of power saving on the isplay board but most of the relevent details are in this thread already, I will start another is that's better.
