I had seen the OpenTx Mega 2560 by some diy people on Rc group .I was wondering if anyone here tried it.I know that 8 bit is a little bit old.but I am hoping someone to have tried it here

Since nobody replied,I am posting here for other who want to build a diy transmitter

Yups the m2560 ones are cool. currently building one as well.

http://www.rcindia.org/self-designed-diy-and-college-projects/flying-on-a-3d-joystick/

Quote from: ghoshatanu56 on June 21, 2017, 04:57:12 AM
I had seen the OpenTx Mega 2560 by some diy people on Rc group .I was wondering if anyone here tried it.I know that 8 bit is a little bit old.but I am hoping someone to have tried it here

Yes the 8 bit arch is a little bit old but it still takes care of what most people want unless you're planning to do any real-time video processing etc

What LCD screen are you using? the JHD12864E types have a different pinout to work with the m2560 based tx

Yes sir you were first in the forum to try mega2560 .I have seen your video using a liner pot( not rotary ones)and another joystick. It came up when I was searching opentx mega in YouTube.

I am using one with st7920 LCD.

Mine with diy multiprotocol module works great

Wow nice 
What module are you using .?

nrf24l01 and cyrf6936 2.4g transmission module
Works with spektrum dsmx protocol
N Chinese protocol on wltoys n hisky

hi folks,good evening , I am new to RCindia
i am trying to build a opentx transmitter with mega2560 with lcd 12864b v.2

i am able to read and write models using open tx companion
connecting using the schematics from opentx

i build the firmware with mega and st7290 but after uploading the firmware and writing through opentx, my lcd is blank

but lcd is working u8glib library with arduino

I dn know why its not working with opentx, need help.



Thanks in advance

Welcome to rci!

I'd troubleshoot in this order..

1) contrast adjustment
2) pinout mapping from 2560 to LCD. the st7920 does not need a CS2 pin connection, it needs not be connected.
3) the required pinout is specified in the MEGA2560_sch.pdf

I have created header boards (shields) that take the 2560 on one side and the ST7920 + the pots and switches on the other side. You can study these for the connections or download the plans and build one for yourself from the link below. If you do not want to build, i have some already fabricated available with me.

https://github.com/gtgs/gt-jtx/tree/master/gt-jtx-2560/hardware

All the best!

thank for helping us out sir i tried with the following configuration, but still have the same problem i followed your troubleshooting guide but still the problem exist
                           LCD 12864B V 2.0 PIN            ARDUINO MEGA 2560 PIN     
                              GND                                               GND
                              VCC                                                 +5V
                              VOUT                                                 NC
                              RS                                                     32
                              R/W                                                   31
                              E                                                       30
                              DB0                                                   22
                              DB1                                                   23
                              DB2                                                   24
                              DB3                                                   25
                              DB4                                                   26
                              DB5                                                   27
                              DB6                                                   28
                              DB7                                                   29
                              PSB                                                   +5V
                              NC                                                      NC
                              RST                                                    33
                              VOUT                                                  NC
                              BLA                                                     5V
                              BLK                                                     GND   
                               

1. Use a potentiometer for the contrast adjustment pin.
pin1 - +5v
pin2 - VADJ pin of LCD - see below
pin3 - GND


2. try the pinout below for the ST7920

LCD 12864B V 2.0 PIN            ARDUINO MEGA 2560 PIN      
                             GND                                               GND
                             VCC                                                 +5V
                             VADJ                                                 center pin of potentiometer
                             RS                                                     32
                             R/W                                                   31
                             E                                                       30
                             DB0                                                   22
                             DB1                                                   23
                             DB2                                                   24
                             DB3                                                   25
                             DB4                                                   26
                             DB5                                                   27
                             DB6                                                   28
                             DB7                                                   29
                             PSB                                                   34
                             NC                                                      NC
                             RST                                                    33
                             VOUT                                                  NC
                             BLA                                                     35
                             BLK                                                     GND  

3. After powering up, see if the LCD lights up (Backlit LED). If open tx is working, the backlight should turn off after a while. if it doesnt turn off, check your program code and if it is flashed correctly. if the backlit LED turns off, check the LCD contrast.

4. Use a multimeter (continuity tester mode) to see the connections and wires are correct.

5. Wire up the other components also, the pot/sticks/switches etc... would recommend not to leave any pins floating before powering up

You will need to be very patient with the setup. it can take a lot of time for debugging so dont give up

Thank you for the help,

i ll try the things u have said  and update .