Hi all,
I have made some mods to my TFT implementation of the display.
MOD. 1 - 9th Jan '25I have always wanted a 1 VDC range for the R6581. Now, we do get a 1000 mV range however I guess I am too used to my 3458A where it will display X.XXXXXXX VDC.
So, I added a new mode whereby if you are on the 1000mV Range and you hit the DCV button it will switch the display out to a new 1 V Range.
It gets its data from the 1000 mV Range and so you get an extra digit, one more than the 10 V Range for instance at max 8.5 digits.
See photo below.
The Blue Pill uses two additional inputs to interface to the DCV button, see photo below.
Two are required because the button is multiplexed and I need two inputs to somewhat read a button press.
GIT source =
https://github.com/Ian-Johnston/R6581_VS_DisplayGIT .HEX file =
https://github.com/Ian-Johnston/R6581_VS_Display/tree/master/VisualGDB/DebugOnly upgrade to this version is you hook up the new inputs to the DCV switch.
New Pcb gerbers attached which include the new A11/A12 connections.
Any issues then let me know (there are a couple of very small things).
PS. For the coders, The Blue Pill doesn't have a hardware FP and the software FP was being a pain, i.e. I wanted to use atof but it just continued to return empty, so I wrote around it (ugghh!). There doesn't seem to be any downsides though. I’ll return to this soon as atof is a lot less code.
UPDATE - 9th Jan '25
Digital input A11/A12 logic tweaked.
UPDATE - 10th Jan '25
1 VDC mode is now quite a bit more seemless, once it is set then it will remain in 1 VDC mode even if overrange or the DMM is in AUTO mode.
GIT hex file updated.
Still to do: try to reverse engineer the keypad better to fully isolate that button.
UPDATE - 15th Jan '25
Vertical Back Porch for TFT set to 11 rather than 10 (10 is per spec!) due to TFT flickering issue when running the R6581T for 20hrs.
Possibly the a heat/stability issue with the LT7680A-R or the TFT itself. They do run pretty warm in there (I might look at a fan upgrade)!
UPDATE - 16th Jan '25
Horizontal Back Porch for TFT set to 30 rather than 20 (20 is per spec!) due to TFT still flickering issue when running the R6581T for 12hrs.
I have attached the original HEX file and this new one.UPDATE - 19th Jan '25
Fix issue where random pixels might appear at right hand vertical edge.
See new HEX file.
MOD. 2 - 10th Jan '25When the LCD shows "DISPLAY OFF" i.e. when the user actions this via the menu, it now turns off the LCD completely (blank). Pressing the MENU button revives.
It reduces the backlight to minimum, and turns off the LCD via register 0x12 of the LT7680.
A user asked for this and I guess it's good for TFT long term saving especially for those running the DMM 24/7.
UPDATE - 12th Jan '25
Bug fix on the backlighting brightness control when implementing DISPLAY OFF.
Ian.