LCD keypad shield on WEMOS D1 R32

Other Hardware Displays
21

bperrybap:
The two transistors are J3Y and the signals that feed it are from a CH430C USB to serial chip running at 5V with 5V logic signals.
So that is likely causing the collector to float up to 4.1 volts as the logic signals connected to the base and emitter are at 5V.

Pulled up by the base-collector junctions. Arguably the base resistors should be 100k rather than 10k.

bperrybap:
But the esp32 "mini" style board uses a different design and has 3.3v on the EN and BOOT pins.

OK, so it powers the CH340 from 3.3 V, why then does the D1 R32 not? :roll_eyes:

22

On the espduino32 board I have, the CH240C connects VCC to USB VBUS for power and V3 connects through cap to gnd.
The cp2102 looks a bit more flexible in that i/o voltage output appears to track vdd rather than vcc.

The "mini" esp32 module that I have uses a cp2102 vs the espduino-32 uses the CH340C.

--- bill

23

smlee0511,
The hd44780 library has been updated to better support the esp32 platform and the espduino32 board.
The new release is version 1.3.1

Depending on the board you have there may be some h/w issues.
So you may have to do some h/w modifications to your WeMos D1 R32 board.

For the board I had, I had to:

  • solder a 10k resistor between GPIO12 and ground
    This h/w fix allows the board to work and download when the keypad shield is plugged in.
    On a espduino32 board it is the header pin for D8

  • solder a 10uf cap between EN and ground.
    EN pin is wired up to the "reset" button and the header pin labled "RST"
    This h/w fix allows the board to download if downloading isn't working and the ide is reporting:
    A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header

I soldered the cap across the "reset" button on the side of the board by the usb connector.

Once you can download to the espduino32, all the included hd44780_pinIO examples should "just work" with the keypad shield plugged in.

One really sad thing is that the esp32 platform does not include an analogWrite() function, so this means that you will not be able to do any backlight dimming using the hd44780 library.
Here is the esp32 platform issue about it:

The esp8266 boards including the Wemos D1 R1 uno form factor boards do not have these issues.

--- bill

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