Working I2C-controlled digits

flake.nix

@@ -26,6 +26,8 @@
             rootFileContent = builtins.readFile rootdir.outPath;
           in
           pkgs.lib.mkIf (rootFileContent != "") rootFileContent;
+
+        ocdInterface = mcu/tigard-swd.cfg;
       in
       {
         devenv.shells.mcu = {
@@ -34,6 +36,7 @@
           packages = with pkgs; [
             gnumake
             cmake
+            pkgsCross.arm-embedded.buildPackages.gdb # ARM one is broken
             gcc-arm-embedded
             python3
             picotool
@@ -43,6 +46,27 @@
           env = {
             PICO_SDK_PATH = "${pkgs.pico-sdk}/lib/pico-sdk";
           };
+
+          scripts = {
+            build.exec = ''
+              cmake -S . -B build -D CMAKE_BUILD_TYPE=Debug -D PICO_STDIO_SEMIHOSTING=1
+              cmake --build build --parallel
+            '';
+            build-rel.exec = ''
+              cmake -S . -B build-release -D CMAKE_BUILD_TYPE=Release
+              cmake --build build-release --parallel
+            '';
+            clean.exec = ''
+              rm -rf build/ build-release/
+            '';
+
+            ocd.exec = ''
+              openocd -f ${ocdInterface} -f target/rp2040.cfg
+            '';
+            gdb.exec = ''
+              arm-none-eabi-gdb -x .gdbinit build/qclk.elf
+            '';
+          };
         };
       };
     };

mcu/.gdbinit

@@ -0,0 +1,4 @@
+target extended-remote localhost:3333
+monitor arm semihosting enable
+monitor reset init
+monitor debug_level -2

mcu/.gitignore

@@ -1 +1,2 @@
 /build/
+/build-release/

mcu/CMakeLists.txt

@@ -6,14 +6,14 @@ include(pico_sdk_import.cmake)
 project(test_project C CXX ASM)
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_C_COMPILER_WORKS ON)
-set(CMAKE_CXX_COMPILER_WORKS ON)
 pico_sdk_init()
 
 add_executable(qclk
   main.c
 )
+
 pico_enable_stdio_usb(qclk 1)
-pico_enable_stdio_uart(qclk 1)
+pico_enable_stdio_uart(qclk 0)
+
 pico_add_extra_outputs(qclk)
-target_link_libraries(qclk pico_stdlib)
+target_link_libraries(qclk pico_stdlib hardware_i2c pico_i2c_slave)

mcu/main.c

@@ -1,23 +1,102 @@
 #include <stdio.h>
-#include "pico/stdlib.h"
+
 #include "hardware/gpio.h"
+#include "hardware/i2c.h"
+#include "pico/stdlib.h"
 #include "pico/binary_info.h"
+#include "pico/i2c_slave.h"
 
-const uint LED_PIN = 25;
+const uint PIN_DIGIT_BASE = 18;
+const uint PIN_SEGMENT_BASE = 2;
 
-int main() {
-  bi_decl(bi_program_description("This is a test binary."));
-  bi_decl(bi_1pin_with_name(LED_PIN, "On-board LED"));
+const uint N_DIGITS = 4;
 
-  stdio_init_all();
+const uint I2C_PIN_SDA = 0;
+const uint I2C_PIN_SCL = 1;
+const uint I2C_SLAVE_ADDRESS = 0x17;
+const uint I2C_RATE = 100 * 1000;
 
-  gpio_init(LED_PIN);
-  gpio_set_dir(LED_PIN, GPIO_OUT);
-  while (1) {
-    gpio_put(LED_PIN, 0);
-    sleep_ms(250);
-    gpio_put(LED_PIN, 1);
-    puts("Hello World\n");
-    sleep_ms(1000);
+uint8_t digit_states[4] = { 0 };
+static struct {
+  bool digit_written;
+  uint digit;
+} i2c_context;
+
+static void write_digit(uint8_t digit) {
+  const uint mask = (0xffffffff << PIN_SEGMENT_BASE) ^ (0xffffffff << PIN_SEGMENT_BASE + 8);
+  gpio_put_masked(mask, (~digit & 0xff) << PIN_SEGMENT_BASE);
+  gpio_put_masked(mask, digit << PIN_SEGMENT_BASE);
+}
+static void setup_io() {
+  for (uint i = PIN_DIGIT_BASE; i < PIN_DIGIT_BASE + N_DIGITS; i++) {
+    gpio_init(i);
+    gpio_set_dir(i, GPIO_OUT);
+    gpio_put(i, 0);
+  }
+  for (uint i = PIN_SEGMENT_BASE; i < PIN_SEGMENT_BASE + 8; i++) {
+    gpio_init(i);
+    gpio_set_dir(i, GPIO_OUT);
+  }
+  write_digit(0);
+}
+static void display_loop() {
+  for (uint i = 0; i < N_DIGITS; i++) {
+    uint prev = i == 0 ? N_DIGITS - 1 : i - 1;
+
+    gpio_put(PIN_DIGIT_BASE + prev, 0);
+    sleep_us(100);
+
+    write_digit(digit_states[i]);
+    gpio_put(PIN_DIGIT_BASE + i, 1);
+    sleep_ms(1);
   }
 }
+
+static void i2c_slave_handler(i2c_inst_t *i2c, i2c_slave_event_t event) {
+  switch (event) {
+  case I2C_SLAVE_RECEIVE: // master has written some data
+    if (!i2c_context.digit_written) {
+        // writes always start with the memory address
+        uint8_t addr = i2c_read_byte_raw(i2c);
+        i2c_context.digit = addr < N_DIGITS ? addr : -1;
+        i2c_context.digit_written = true;
+    } else if (i2c_context.digit != -1) {
+        // save into memory
+        digit_states[i2c_context.digit] = i2c_read_byte_raw(i2c);
+    }
+    break;
+  case I2C_SLAVE_REQUEST: // master is requesting data
+    // load from memory
+    uint8_t data = i2c_context.digit != -1 ? digit_states[i2c_context.digit] : 0;
+    i2c_write_byte_raw(i2c, data);
+    break;
+  case I2C_SLAVE_FINISH: // master has signalled Stop / Restart
+    i2c_context.digit_written = false;
+    break;
+  default:
+    break;
+  }
+}
+static void setup_i2c() {
+  gpio_init(I2C_PIN_SDA);
+  gpio_set_function(I2C_PIN_SDA, GPIO_FUNC_I2C);
+  gpio_pull_up(I2C_PIN_SDA);
+
+  gpio_init(I2C_PIN_SCL);
+  gpio_set_function(I2C_PIN_SCL, GPIO_FUNC_I2C);
+  gpio_pull_up(I2C_PIN_SCL);
+
+  i2c_init(i2c0, I2C_RATE);
+  // configure I2C0 for slave mode
+  i2c_slave_init(i2c0, I2C_SLAVE_ADDRESS, &i2c_slave_handler);
+}
+
+int main() {
+  bi_decl(bi_program_description("qCLK driver."));
+
+  stdio_init_all();
+  setup_io();
+  setup_i2c();
+
+  while (1) display_loop();
+}

mcu/tigard-swd.cfg

@@ -0,0 +1,8 @@
+adapter driver ftdi
+transport select swd
+ftdi_vid_pid 0x0403 0x6010
+ftdi_channel 1
+adapter speed 2000
+ftdi_layout_init 0x0028 0x002b
+ftdi_layout_signal SWD_EN -data 0
+ftdi_layout_signal nSRST -data 0x0020