Display SPI Connections on Lolin Pico 3

Other Hardware Displays
1

Hello,
I have a Waveshare 7.5" e-Ink Display v3 (840x400) and would like to run it on a Lolin c3 Pico.
I already managed to run the Display on a common wroom32 but this Lolin Pico has a bit more challenging PIN Layout.

Schematics:

Datasheet for c3:

now I have this in the code:

// Pins for Waveshare e-paper Driver Board
const uint8_t PIN_EPD_BUSY = 2;
const uint8_t PIN_EPD_CS   = 5;
const uint8_t PIN_EPD_RST  = 10;
const uint8_t PIN_EPD_DC   = 8; //
const uint8_t PIN_EPD_SCK  = 1;
const uint8_t PIN_EPD_MOSI = 4;

But I hit a dead end with the combinations I tried so far, sometimes ending in "Busy Timeout!" or something along

ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x3 (RTC_SW_SYS_RST),boot:0xd (SPI_FAST_FLASH_BOOT)
Saved PC:0x403819b6
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd5810,len:0x438
load:0x403cc710,len:0x918
load:0x403ce710,len:0x24e4
entry 0x403cc710

I have seen in the Datasheet that

For ESP32-C3FH4AZ, pins within the frame (namely pin 19 ∼ pin 24) are not bonded, and are labelled as ”not connected”.

Does this mean I don't have CS0 and also no CLK ?

Maybe you can give me a learning moment when reading all these documents, thank you very much!

ESP32 S2 mini custom SPI with GxEPD2
2

Here is the Lolin C3 Pico Documentation, I cannot post more than 3 links as new user:
https://www.wemos.cc/en/latest/c3/c3_pico.html#documentation

Oh and the Code Project I'm cloning is here:

3

Sorry but I do not want to wander the WWW to be able to guess what you have. Posting an annotated schematic as you have wired it will help a lot. Be sure to show all connections and power supplies.

4

Oh sorry I did not mean to miss stuff in my original post.

I use these connections:

EPD_BUSY     => Pin 2
EPD_CS       => Pin 5
EPD_RST      => Pin 10
EPD_DC       => Pin 8
EPD_SCK      => Pin 1
EPD_MOSI     => Pin 4

If you look at it from the board perspective this is how I wired it up:

Untitled-2
Untitled-21800×900 264 KB

in terms of GxEPD2 looks like this:
BUSY -> 2, RST -> 10, DC -> 8, CS -> 5, CLK -> SCK(1), DIN -> MOSI(4), GND -> GND, 3.3V -> 3.3V

5

GxEPD2 uses HW SPI. On ESP32C2, ESP32C3, ESP32S2, ESP32S3 the pins used depend on the board you select to compile for. So please report this also.

e.g.: esp32c3/pins_arduino.h:

static const uint8_t SS    = 7;
static const uint8_t MOSI  = 6;
static const uint8_t MISO  = 5;
static const uint8_t SCK   = 4;

e.g. lolin_c3_mini/pins_arduino.h:

static const uint8_t SS    = 5;
static const uint8_t MOSI  = 4;
static const uint8_t MISO  = 3;
static const uint8_t SCK   = 2;

You could re-map the pins if needed.

Jean-Marc

6

Thank you @ZinggJM for responding so quick!

In Vscode I compile for lolin_c3_mini
In Arduino IDE I try a simple hello world sketch also with Lolin C3 Mini as for both there is no specific Pico 3 available.

I see that lolin_c3_mini pins map SCK to 2, but the Wemos Documentation shows SCK on 1 for the Pico so I guess I need to rewrite that? Thats where my confusion starts :smiley:

Or do i just wire up the driver hat's CLK to Pin 2?

Grüße aus Tirol!

7

That's up to you. Both options are equivalent (SPIClass maps HW SPI pins according to pins_arduino.h). You can pre-map by calling SPI.begin(...) before display.init(...) in GxEPD2, then the GxEPD2 call of SPI.begin() has no effect.

I think the documentation uses the pins like for ESP8266 Wemos D1 mini shields, but someone got the pins_arduino.h wrong. Not verified yet.

Servus von Luzern und Umgebung.

1 Like
8

can confirm that indeed Pin 2 is the SCK I can use in GxEPD2. Which is what threw me off!

works beautiful, thank you very much for your help and the awesome work in GxEPD!

9

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