Trying to connect/use a small LED screen with SPI (ssd1351 controller)

whoman421 · January 2020

Hi Hi!

I've been trying to use a Waveshare 1.5" RGB LED screen with the ROC-RK3328-CC using SPI (running the libre debian image for this board) but am very new to SPI devices and am not sure of a few things.

I'm using LUMA-OLED python library (with the help of R64-GPIO python library) and just trying to use the examples that come with it (I already have an i2c LED screen working), however I am unsure of a few things regarding the SPI hardware connection and software configuration:

Hardware:

Am I supposed to be using GPIO3 for something like this?

I've only been finding info of people wiring these LED screens to Raspberry Pis, and I'm not 100% sure I've got the pins plugged in correctly:

DIN - GPIOTX pin 19?

CLOCK - pin 23?

Chip Select - pin 24?

DC or Data/Command - which pin?

Reset - which pin?

in LUMA-OLED's documentation, it states that you need to connect RESET and DC pins to GPIO 24 and 25 on a raspberry pi, so does that mean that somewhere in the LUMA-OLED code, that is hard coded? I'm just wondering what I may need to find/change to make sure the software is trying to speak on the right pins considering this isn't a RPi.

Software:

is "cat /sys/kernel/debug/gpio" the SPI equivalent to i2detect for i2c?

is that how I would confirm that my SPI device is being recognized?

how would I go about "setting" those GPIO pins to be in the proper modes?

Any help would be supremely appreciated.

Thanks

P.S. Output of "cat /sys/kernel/debug/gpio":

firefly@firefly:/sys/kernel/debug$ cat gpio
GPIOs 1000-1031, platform/pinctrl, gpio0:
gpio-1000 ( |vcc_host_5v ) out hi
gpio-1025 ( |? ) out lo
gpio-1030 ( |vcc_sd ) out lo

GPIOs 1032-1063, platform/pinctrl, gpio1:
gpio-1050 ( |mdio-reset ) out hi
gpio-1058 ( |vcc_host1_5v ) out hi

GPIOs 1064-1095, platform/pinctrl, gpio2:

GPIOs 1096-1127, platform/pinctrl, gpio3:

GPIOs 1510-1511, platform/rk8xx-gpio, rk8xx-gpio, can sleep:
gpio-1510 ( |? ) out hi
gpio-1511 ( |? ) out lo

whoman421 · January 2020

Also just in case, when I try to execute any of the examples in luma.examples, I get the following:

sudo python 3d_box.py -i spi --display ssd1351 --spi-port 3
Version: luma.oled 3.3.0 (luma.core 1.12.0)
Display: ssd1351
Interface: spi
Dimensions: 128 x 64
------------------------------------------------------------
Error: Unable to export GPIO
Error: Unable to set GPIO direction
Error: Unable to export GPIO
Error: Unable to set GPIO direction
You must setup() the GPIO channel (BCM 25) as an output first
You must setup() the GPIO channel (BCM 25) as an output first
usage: 3d_box.py [-h] [--config CONFIG] [--display DISPLAY] [--width WIDTH]
                 [--height HEIGHT] [--rotate ROTATION] [--interface INTERFACE]
                 [--i2c-port I2C_PORT] [--i2c-address I2C_ADDRESS]
                 [--spi-port SPI_PORT] [--spi-device SPI_DEVICE]
                 [--spi-bus-speed SPI_BUS_SPEED] [--spi-cs-high SPI_CS_HIGH]
                 [--spi-transfer-size SPI_TRANSFER_SIZE]
                 [--ftdi-device FTDI_DEVICE] [--gpio GPIO]
                 [--gpio-mode GPIO_MODE]
                 [--gpio-data-command GPIO_DATA_COMMAND]
                 [--gpio-reset GPIO_RESET] [--gpio-backlight GPIO_BACKLIGHT]
                 [--block-orientation ORIENTATION] [--mode MODE]
                 [--framebuffer FRAMEBUFFER] [--bgr] [--h-offset H_OFFSET]
                 [--v-offset V_OFFSET] [--backlight-active VALUE]
                 [--transform TRANSFORM] [--scale SCALE] [--duration DURATION]
                 [--loop LOOP] [--max-frames MAX_FRAMES]
3d_box.py: error: SPI device not found

brandonme · February 2020

Have you enabled spi with the overlay tool?

whoman421 · February 2020

Thanks so much for your reply.

I have not, as was using the libre debian image which I believe does not have dt overlay available.

So I've also downloaded the armbian images in an attempt to use the overlays to enable SPI however I cannot find any info on an "overlay tool".

The "README.rockchip-overlays" in the "/boot/dtb/rockchip/overlay" folder gives some details of manually using overlays, and all I could find online regarding dt overlays was at: https://docs.armbian.com/User-Guide_Allwinner_overlays/

Although not for Rockchip, it seems to be a generic document which also explains how to manually add overlays.

Can you let me know where I can find this "overlay tool", or any link to pages ragarding this tool's usage?

I really appreciate any tips you may have on this.

Thanks again!

P.S.

With the armbian images, the output of "cat /sys/kernel/debug/gpio" looks like this:

gpiochip0: GPIOs 0-31, parent: platform/pinctrl, gpio0:
gpio-30 (                    |sdmmc-regulator     ) out lo ACTIVE LOW

gpiochip1: GPIOs 32-63, parent: platform/pinctrl, gpio1:
gpio-50 (                    |snps,reset          ) out hi ACTIVE LOW
gpio-58 (                    |vcc-host1-5v-regulat) out hi

gpiochip2: GPIOs 64-95, parent: platform/pinctrl, gpio2:

gpiochip3: GPIOs 96-127, parent: platform/pinctrl, gpio3:

gpiochip4: GPIOs 511-511, parent: platform/ff100000.syscon:grf-gpio, ff100000.syscon:grf-gpio:
gpio-511 (                    |vcc_sdio            ) out lo

whoman421 · February 2020

Also, the SPI pins specified in the RockChip Overlay Readme for SPIDEV are as follows:

SPI 0 pins (MOSI, MISO, SCK, CS): GPIO3_A5, GPIO3_A4, GPIO3_A6, GPIO3_A7
SPI 1 pins (MOSI, MISO, SCK, CS): GPIO1_A7, GPIO1_B0, GPIO1_B1, GPIO1_B2
SPI 2 pins (MOSI, MISO, SCK, CS): GPIO1_C0, GPIO1_B7, GPIO1_C1, GPIO1_C2
SPI 3 pins (MOSI, MISO, SCK, CS): GPIO2_B2, GPIO2_B1, GPIO2_B3, GPIO2_B4

However the only document I could find showing the GPIO pins for the ROC-RK3328-CC doesn't have these pin numbers for the specified GPIOs:

Is there a better document out there which specifies the ROC-RK3328-CC GPIO pin numbers?

That image I linked to is the only one I could find, and it was in the following forum post:

whoman421 · February 2020

So I've edited /boot/armbienEnv.txt and added the following 2 lines:

overlays=spi-spidev
param_spidev_spi_bus=0

after reboot, I still get nothing for:

dmesg | grep spi

and there is no /dev/spidev device files present.

Is there a step I'm missing to enable SPI?

Thanks

Kulibali · July 2021

It always seemed to me that it was very difficult to understand all this.

Trying to connect/use a small LED screen with SPI (ssd1351 controller)

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