Raspberry Pi Zero 2 On PicoCalc

jblanked · October 17, 2025, 1:38am

I finally got done with this (took about 10 hours or so of planning and getting my fingers hurt lol)

Now I can connect a Pico or Zero without removing the back panel

michael_mayer · October 17, 2025, 5:41am

That made me think about the edge connector/cartridge design again.

Maybe:

maple · October 17, 2025, 12:20pm

close enough welcome back handspring visor springboard modules

n602_na · October 17, 2025, 1:43pm

I considered various options for the 5V Booster and I2C Repeater for my new relay board.
In the end, I decided it would be best to give the user the option of whether or not to use them

In other words, I designed it so that it would be possible to create boards with the following specifications:

A board with an I2C Repeater (PCA9515) and a 5V Booster (Pololu U3V40F5)
A board with only an I2C Repeater (PCA9515)
A board without either an I2C Repeater or a 5V Booster

newbd011200×900 219 KB

newbd021024×768 187 KB

If the 5V Booster is not included, one additional wire will be required.(the red wire shown in the photo).
If the I2C Repeater is not included, one pattern cut (cutting the 3.3V line) and two additional wires (SDA, SCL) will be required. These are relatively simple changes, so there shouldn’t be any problems.

I’ll test this board for a while to see if it works properly.

michael_mayer · October 17, 2025, 2:51pm

Great design!

What about the other connection that are omitted by now?

Picocalc SD Card reader
GPIO Side pins
…

Maybe we should think about how to connect them and write software/configuration for it.

What do you think?

jblanked · October 18, 2025, 12:00am

I managed to make the desktop appear smaller. I’m not sure if I did it the right way, but I went into Preferences → Display and then clicked For Smaller Screens

Is there a better way? All the windows (except for some games I tried) do fit within the screen now (even after rebooting)

n602_na · October 18, 2025, 4:16am

Thank you.
Yes, it would be great if the SD slot on the PicoCalc itself and some of the GPIO on the RasPiZero2W could be used.

—About SD card slot
The PicoCalc’s SD card slot is controlled via SPI and powered by the AXP2101, so I think it should work if I connect it to the RasPiZero2W’s SPI.
I’m concerned about SD_DET. According to the circuit diagram, SD_DET is pulled up to 3V3_OUT with a 10K ohm resistor.
The wiring shown in “Raspberry Pi Zero 2 on PicoCalc” doesn’t include a connection from the RaspiZero2W’s 3.3V to 3V3_OUT, so SD_DET’s ability to determine the presence of the SD card may be impossible or unreliable.
If SD_DET can be ignored, that won’t be a problem.
If the wiring is done using a different SPI system from the LCD, it may look like this:

RasPICO GPIO — RasPiZero2W GPIO
SPI0_CS GP17 — GP18
SPI0_SCK GP18 — GP21
SPI0_TX GP19 — GP20
SPI0_RX GP20 — GP19
SD_DET GP22 — ?

I think there are some complicated steps to make the SD card usable by Raspbian.
It might be easier to attach an SD card reader to the USB port on the RaspPiZero2W.

— About GPIO
I think it’s a great idea and practical to expose all or some of the RasPiZero2W’s GPIO so that it can be used.
Since it would be impossible to expose all GPIO, I2C and UART, which are likely to be used frequently, would probably be good candidates.

With I2C, if a GROVE terminal can be added to the edge of the board, various experiments will become possible.
I tried this with GP4 and GP5, avoiding GP2 and GP3, which are for the I2C keyboard.
I connected an SHT35 sensor via I2C and was able to measure temperature and humidity.

It might be possible to do the same for UART(GPIO14/15?) by adding a connector of some kind.
There are probably other GPIOs that are suitable, but there may not be any spare space on the board.

P.S.
Oh, I misunderstood.
Does that mean that some of those GPIOs just need to be wired to the GPIO socket on the side of the PicoCalc?

I wired the GPIO socket on the side of PicoCalc as shown below.

3V3
I2C_SDA — PicoCalc GP2 — RasPi GP4(7pin) SDA
I2C_SCL — PicoCalc GP3 — RasPi GP5(29pin) SCL
UART_Tx — PicoCalcGP4 — RasPi GP14(8pin) Tx
UART_Rx — PicoCalcGP5 — RasPi GP15(10pin) Rx
PicoCalc GP21 — RasPi GP?? [unwired]
PicoCalc GP28 — RasPi GP?? [unwired]
GND

I see, this is convenient.

michael_mayer · October 18, 2025, 8:42am

Hi,

Thanks for Insights and toughts.

I think sd card will be possible because it was made possible with the lyra fox. I will check if i find the configuration in @hisptoot github repsitory.

“I wired the GPIO socket on the side of PicoCalc as shown below.”

That is what I meant.

Another thought is:

My case design allows access to the PI Zero GPIO pin on the back.

So I can maybe design some kind of backpack Extensions.

I will try something this week with kicad.

n602_na · October 18, 2025, 9:55am

That’s a great idea!
I look forward to your SD developments and new case designs.

9a4db · October 21, 2025, 9:03am

Letter arrived today.

THANK YOU!

michael_mayer · October 21, 2025, 9:49am

22 days lol. BTW. I have still boards to give away. (Still not to US because of the tax situation)

7 Boards are still available.

jblanked · October 21, 2025, 4:56pm

I just tested the 64-bit version and it worked!

However I had to remove this line from setup_keyboard.sh

github.com/ironat/picocalc_trixie

setup_keyboard.sh

a0e4411b7


      
          MODULE_NAME=picocalc_kbd
          SRC_DIR=./picocalc_kbd
          DTBO_DIR=./picocalc_kbd/dts
          KO_FILE=${MODULE_NAME}.ko
          DTBO_FILE=${MODULE_NAME}.dtbo
          
          echo "🔧 Step 1: Installing dependencies..."
          sudo apt update
          sudo apt install -y \
              build-essential \
              kernel-package \
              device-tree-compiler \
              git
          
          echo "🔧 Step 2: Building kernel module in ${SRC_DIR}..."
          make -C /lib/modules/$(uname -r)/build M=$(realpath ${SRC_DIR}) modules
          
          echo "📁 Step 3: Installing kernel module to system..."
          sudo mkdir -p /lib/modules/$(uname -r)/extra
          sudo cp ${SRC_DIR}/${KO_FILE} /lib/modules/$(uname -r)/extra/
          sudo depmod

michael_mayer · October 21, 2025, 5:08pm

Interesting. Have you done the stuff with the apt Parameters? Maybe it is installed with another Package. How does it runs with 64 bit?

jblanked · October 21, 2025, 5:18pm

It’s running alright so far. No issues yet!

I did do the apt parameters:

APT::Install-Suggests "false";
APT::Install-Recommends "false";

but I also installed some stuff I use for development before installing the display/keyboard drivers

michael_mayer · October 21, 2025, 6:49pm

Ah, Maybe you installed the Headers accidently. I think they maybe also be called something with 64.

I have not tried 64 bit by now.

But it is great that it works.

Guidouil · October 22, 2025, 7:03am

Are you going to make a video to help me do it too ?
Or it’s just the same as Michael github just choosing a different os and this line in the script ?
Thanks

EDIT:
I tried it myself and I validate the error for this line in setup_keyboard.sh
The error message is : Error: Unable to locate package kernel-package
Beside that it runs like a charm

Cs137 · October 22, 2025, 11:06am

Hi Michael,
I would be highly interested in a board or two, in case there are still some to give away. It does not have a high priority, since I am waiting for my PicoCalc. But I would like to have things in place when it arrives. Many thanks for the efforts you and the others put into this nice project and regards from DE!

jblanked · October 22, 2025, 11:20am

Awesome glad you figured it out!! It’s the same steps but without that kernel line

To my knowledge, the 64-bit versions already have a 64-bit kernel installed

reynolds_live · October 26, 2025, 1:21pm

@michael_mayer Great job on the trixie port! I am a bit confused about your github instructions on the battery add on and how to set that up.

I also notice that pico-8 is still giving me the framerate error. I made sure my clockspeed was at 50 and still get it. Fiddled around with 60 on the clockspeed but no results.

michael_mayer · October 26, 2025, 2:04pm

About pico:

Have you set also the SPI speed?

dtoverlay=mipi-dbi-spi,spi0-0,speed=70000000

You need the clock and the speed parameter.

The battery indicator only works with tmux.

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Raspberry Pi Zero 2 On PicoCalc

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