Org on Github
# ==========================================================
PICO_SDK_FETCH_FROM_GIT=1 PICO_EXTRAS_FETCH_FROM_GIT=1 cmake -DCMAKE_TOOLCHAIN_FILE=../pico_arm_gcc_toolchain.cmake .. -DCMAKE_C_FLAGS="-mcpu=cortex-m0plus -mthumb"  -DCMAKE_CXX_FLAGS="-mcpu=cortex-m0plus -mthumb" -DCMAKE_ASM_FLAGS="-mcpu=cortex-m0plus -mthumb"

compile here:
# ==========================================================
PICO_SDK_FETCH_FROM_GIT=1 PICO_EXTRAS_FETCH_FROM_GIT=1 cmake -DCMAKE_TOOLCHAIN_FILE=/home/pi/pico/pico-sdk/cmake/preload/toolchains/pico_arm_cortex_m0plus_gcc.cmake .. -DCMAKE_C_FLAGS="-mcpu=cortex-m0plus -mthumb"  -DCMAKE_CXX_FLAGS="-mcpu=cortex-m0plus -mthumb" -DCMAKE_ASM_FLAGS="-mcpu=cortex-m0plus -mthumb"

cp ../../pico-sdk/external/pico_sdk_import.cmake .


CMakeLists.txt Line 59

from
# ==========================================================
pico_enable_stdio_usb(${PROJECT} 1)  # Enable USB serial
pico_enable_stdio_uart(${PROJECT} 0) # Disable UART serial
# ==========================================================

to
# ==========================================================
# Enable USB and UART output
pico_enable_stdio_usb(${PROJECT} 0)  # Disable USB serial
pico_enable_stdio_uart(${PROJECT} 1) # Enable UART serial
# ==========================================================


Edit main.c Header - includes and defining UART
# ==========================================================
#include <stdio.h>
#include <string.h>
#include "pico/stdlib.h"
#include "pico/audio_pwm.h"
#include "hardware/uart.h"
#include "hardware/gpio.h"
#include "hardware/clocks.h"

#include "epsonapi.h" // import DECtalk 4.99

// Define UART
#define UART_ID uart0
#define BAUD_RATE 9600
#define UART_TX_PIN 0
#define UART_RX_PIN 1

...

    // Now init USB serial at the correct clock speed
    stdio_init_all();

    // Set up our UART
    uart_init(UART_ID, BAUD_RATE);



# ==========================================================


su pi
export PICO_SDK_PATH=/home/pi/pico/pico-sdk

cd /home/pi/
# mkdir pico
cd pico
git clone https://github.com/dectalk/DECtalkMini.git dectalkmini
cd dectalkmini/pico
cp ../../pico-sdk/external/pico_sdk_import.cmake .
export PICO_SDK_PATH=/home/pi/pico/pico-sdk
nano  CMakeLists.txt
nano main.c
mkdir build
cd build
PICO_SDK_FETCH_FROM_GIT=1 PICO_EXTRAS_FETCH_FROM_GIT=1 cmake -DCMAKE_TOOLCHAIN_FILE=/home/pi/pico/pico-sdk/cmake/preload/toolchains/pico_arm_cortex_m0plus_gcc.cmake .. -DCMAKE_C_FLAGS="-mcpu=cortex-m0plus -mthumb"  -DCMAKE_CXX_FLAGS="-mcpu=cortex-m0plus -mthumb" -DCMAKE_ASM_FLAGS="-mcpu=cortex-m0plus -mthumb"
make -j$(nproc)





# ==========================================================
# ==========================================================


mkdir build

cd build

PICO_SDK_FETCH_FROM_GIT=1 PICO_EXTRAS_FETCH_FROM_GIT=1 cmake -DCMAKE_TOOLCHAIN_FILE=/home/pi/pico/pico-sdk/cmake/preload/toolchains/pico_arm_cortex_m0plus_gcc.cmake .. -DCMAKE_C_FLAGS="-mcpu=cortex-m0plus -mthumb"  -DCMAKE_CXX_FLAGS="-mcpu=cortex-m0plus -mthumb" -DCMAKE_ASM_FLAGS="-mcpu=cortex-m0plus -mthumb"

make -j$(nproc)



PICO_SDK_FETCH_FROM_GIT=1 
PICO_EXTRAS_FETCH_FROM_GIT=1 
cmake -DCMAKE_TOOLCHAIN_FILE=../pico_arm_gcc_toolchain.cmake .. 
-DCMAKE_C_FLAGS="-mcpu=cortex-m0plus -mthumb"  
-DCMAKE_CXX_FLAGS="-mcpu=cortex-m0plus -mthumb" 
-DCMAKE_ASM_FLAGS="-mcpu=cortex-m0plus -mthumb"