My project has been using the buydisplay 4.3" with the capacitive touch powered with a T3.6 and it works great. I now would like to use a larger display so I purchased four of their 7" with capacitive version. Same RA8875 driver chip and same pinouts and both are 3.3v version(J8 shorted).In my setup I changed the tft.begin(RA8875_480x272) to tft.begin(RA8875_800x480). Neither of the 7" displays work. My question is what could I be missing for the 4.3" to work fine but the 7" displays not. I'm using a ribbon cable so the pins do not change. Thank you
RA8875 issue
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KurtE
Senior Member+
Hard to say... How are you powering the display? Do you have external 3.3v power or are you trying to power it off of the teensy? Note: I am not an expert on their displays, I use them just enough to hopefully
fix or extend some of their drivers.
Neither work? In what way?
Are you sure you ordered a RA8875 display or like the 7" displays I have from them are RA8876. One I just unpacked today... I do see they do carry RA8875 7".
Maybe post a link to what you ordered.
Are they configured the same? For example are they all hardware jumpered to be the same: For example mine were configured for 4 wire SPI?
Are the backlights configured the same. For example one of mine was configured to use internal PWM for backlight and the new one was configured to use an external pin.
Again if you are using the 3.3v VR of the Teensy, very likely not enough power... I have mine configured for 5v.
What software are you using?
Again unclear on configuration. Also when you go up to 800x480 if you are using layers, you can only do so in 8 bit mode. ...
Also I would double check the jumpers on your display to make sure it is what you think it is supposed to be.
fix or extend some of their drivers.
Neither work? In what way?
Are you sure you ordered a RA8875 display or like the 7" displays I have from them are RA8876. One I just unpacked today... I do see they do carry RA8875 7".
Maybe post a link to what you ordered.
Are they configured the same? For example are they all hardware jumpered to be the same: For example mine were configured for 4 wire SPI?
Are the backlights configured the same. For example one of mine was configured to use internal PWM for backlight and the new one was configured to use an external pin.
Again if you are using the 3.3v VR of the Teensy, very likely not enough power... I have mine configured for 5v.
What software are you using?
Again unclear on configuration. Also when you go up to 800x480 if you are using layers, you can only do so in 8 bit mode. ...
Also I would double check the jumpers on your display to make sure it is what you think it is supposed to be.
Hi Kurt, I really appreciate you taking the time to respond.
This is the display I've ordered
https://www.buydisplay.com/7-inch-lcd-module-capacitive-touch-screen-panel-i2c-spi-serial
And this is the 4.3" display I'm currently using.
https://www.buydisplay.com/4-3-inch-tft-lcd-display-capacitive-touchscreen-ra8875-controller
The configurations for both are (3.3v ,3 wire SPI).
My initial thought was not enough power but my on board power supply is capable of 10x the power that the driver requires for the 3.3v option.
I'm using the sumotoy RA8875 library. I created a simple sketch just to print some bitmaps and a "Hello world" to the screen. The 4.3" shows the images but the 7" shows no backlight or anything.
This is the display I've ordered
https://www.buydisplay.com/7-inch-lcd-module-capacitive-touch-screen-panel-i2c-spi-serial
And this is the 4.3" display I'm currently using.
https://www.buydisplay.com/4-3-inch-tft-lcd-display-capacitive-touchscreen-ra8875-controller
The configurations for both are (3.3v ,3 wire SPI).
My initial thought was not enough power but my on board power supply is capable of 10x the power that the driver requires for the 3.3v option.
I'm using the sumotoy RA8875 library. I created a simple sketch just to print some bitmaps and a "Hello world" to the screen. The 4.3" shows the images but the 7" shows no backlight or anything.
KurtE
Senior Member+
I don't have that one, I do have a couple of the 4.3s.
Again mine are both 5v, but if your board has it's own 3.3v VR...
Library, sumotoy - has not been active with it for a long time.
A few of us worked on it, I am not sure if the best fork/branch is at:
https://github.com/Paulstoffregen/RA8875/tree/RA8875_t4
or https://github.com/mjs513/RA8875/tree/RA8875_t4
Which is the one that I typically against...
Which I believe Paul's fork of mjs513 is the one that is included in the version that is included in Teensyduino.
I don't believe any of our libraries support 3 wire SPI.
I know that all of mine are configured for 4 wire SPI.
If I were you, I would check your 4.3s and see how they are configured, mine are off of the pdf:
And then check your new ones and see if it is 3 wire... If so you can update the jumpers.
Again mine are both 5v, but if your board has it's own 3.3v VR...
Library, sumotoy - has not been active with it for a long time.
A few of us worked on it, I am not sure if the best fork/branch is at:
https://github.com/Paulstoffregen/RA8875/tree/RA8875_t4
or https://github.com/mjs513/RA8875/tree/RA8875_t4
Which is the one that I typically against...
Which I believe Paul's fork of mjs513 is the one that is included in the version that is included in Teensyduino.
I don't believe any of our libraries support 3 wire SPI.
I know that all of mine are configured for 4 wire SPI.
If I were you, I would check your 4.3s and see how they are configured, mine are off of the pdf:
And then check your new ones and see if it is 3 wire... If so you can update the jumpers.