i acquired 2 unos for pennys , so i decided to create a project with 2 unos linked, i brought an lcd that sd card reader built in and some Dupont , im a 100% beginner , anyway been tinkering on and off for a few weeks, long story short had sd and lcd initialize in separate ides, uno 1 controls sd and gives lcd and uno 2 power from usb in uno 1 , uno 2 displays everything (when it works) on lcd and the 2 unos communicate back and forth , everything initializes as i said but i cant get rid of the white screen , this is my setup , cant change too much but would like advice on something i may be able to alter to fix it , thank you for any help
i have tried many 5 , 3 v combinations as its spread over 2 unos , uno 1 is all sd , uno 2 is lcd based , the setup i have seems to power everything ok, when usb is removed from uno 2 it stays powered , everything initializes , its just this darn white screen , this is a manual i found ,its basically my manual pin setup http://www.lcdwiki.com/res/MAR2406/2.4inch_Arduino_8BIT_Module_MAR2406_User_Manual_EN.pdf
ive also pulled my project apart put lcd directly into an uno and it worked fine , its almost certain a pin problem, chatgpt aint much help
i have tried this , ive had 2 grounds between the unos , but various problems ensue , this setup works the best so far , stable ,everything initializes and uno 2 is powered by uno 1 when no usb inserted , just the white screen
have you tested the display connected to a UNO with nothing else connected?
testing a similar display plugged into a UNO with the MCUFRIEND_kbv library running program File>Examples>MCUFRIEND_kbv>GLUE_Demo_320x240 it displays
EDIT: the above test was run with the display plugged into an official UNO (with the ARDUINO label)
tried it on another UNO (no label) and I just get a white screen???
EDIT2: plugged into a Mega works OK
EDIT3: tried 3.5" TFT_LCD works OK on official UNO and a Mega - on "another UNO" just get black screen - looks like a power supply problem??
i tried the adafruit gfx demo and get whte screen , tried the one u suggested just now and same thing . this is a legit uno , uno 1 that runs sd is the ropey one in my opinion , i have tore my project down and plugged directly into uno and it works, ive had it working over the 2 unos already and had them conversing but sorted wires so sd is run by uno 1 etc snd this is when the white screen began , i dont think its a power issue , i have tried so many combinations of 5 v 3 v gnd between everything and this setup i have is stable
Ive completly stripped my prioject down and rebuilt for the 1000% this time to how i think it would work and ut does , screen works , sd card is readable and editable just unos are haveing trouble communicating between each other , i think its the rx tx which goes to a breadboard then off to pin 6 and 7 on uno 2 , even tried in rx tx on uno 2 but no coms anyway , how can i test the rx tx is working on the breadboard? Also have brouht this
Are you for some reason trying to control the SD with one UNO and the display with another? Better to have one UNO controlling the combined SD and display, and the 2nd UNO doing whatever processing / data manipulation you intend.
I was...to streamline wires etc but no , now sd and lcd are controlled by uno 1 , uno 2 is powred by uno 1 and send s recives msgs via tx rx and all convo is displayed on screen, everything works bar the communicating back and forth, the rx rx go via a breadboard as i plan to add wifi ao they can go online..but havemt got that far yet..
There are not really many pins left on the UNO with the display. If there is no intent to connect that UNO to USB, then the hardware Rx & Tx pins can be used, but you will need to disconnect those while loading a sketch. The 2nd UNO can then communicate with whatever WiFi board you have using software serial, although that severely limits the speed of communications. If you need USB communications on the 2nd UNO, as well as WiFI and the 1st UNO, that is especially problematic since using two instances of software serial is very difficult to get working.
Its possible to use that type display with an ESP32 and not use the UNOs at all.
You are right , the lcd and sd use 99% of pins on uno 1 , uno 2 has next to no pins used , just pin 6 and 7 from breadboard being used as tx rx and gnd direct from uno 1, the only issue i have at the moment is the unos communicating via tx rx through a breadboard
I havent got the wifi modeule connected yet , all i need help on at the moment is the correct way to connect rx tx to a breadboard and pin placement to take it off to another uno to send data betwen 2 unos with breadboard in-between
