My latest project is a prototype I2C RGB LCD display board with added EEPROM and some other extras.
I decided to do some more work on the Programmable Voltage Reference project, after a long run of test equipment cleanup and repairs.
A specific area of the project that I wanted to tackle was the automation of the calibration procedure, and the possibility of multiple calibration offsets at different temperatures. Another current limitation of the PVR is that it can only directly display the voltage set point.
It would be fairly easy to cycle thru the Set point, Output voltage, Voltage difference, and Mode by just using the existing display and update the display once a second with the next value. Or even dedicating another push-button switch to cycle thru the displays.
The characters on the RGB-LCD display are significantly smaller and will be harder to read from a distance, but can display much more information all at once. Another advantage is using the RGB color back-lighting as a status indicator instead of the rotary encoders RGB led.
I changed around my existing V4.23 RGB-LCD display board by removing the DS3231 RTC (Real Time Clock) IC and added a Microchip Technology 24LC64T‑I/SN 64K EEPROM chip. I also made some other changes to the board such as adding an extra I/O pin and +5 to the JP3 header. The EEPROM footprint is the same as the larger 128K EEPROM 24LC128‑I/SN I.C. which would make it easy to upgrade to a larger EEPROM in the future.
I have also recently designed an inline EEPROM board for my existing PVR units with the 4 digit 7 segment displays.
Boards have arrived from OSH Park.
The next part of the project is to work on changing the code to use the external EEPROM, instead of the run-length encoded data stored on the internal Teensy 3.2 EEPROM.
After finishing the Teensy code the next task is to automate the calibration offset measurements and storing the data into the external EEPROM. My current plan is to use Excel to set the PVR output voltage using serial comm’s and reading the voltage with my Keithley 2015 and the internal Teensy ADC. Then calculate the difference from the set-point and write the offset values for the output DAC and the Teensy internal ADC using the comm port.
After calibration is completed for all 4,095 settings, the system will verify the output with offsets applied.
OSH Park shared I2C RGB LCD Display 4.24 W/eeprom project
EagleCAD Schematic and board files ZIP for Display V4.24 EEPROM