From 5c49f7c2e46d6fced0763094ec05bba41298cbed Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Thu, 25 Jul 2024 13:28:55 -0700
Subject: Initial working version.

---
 rivulet.cpp | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 rivulet.cpp

(limited to 'rivulet.cpp')

diff --git a/rivulet.cpp b/rivulet.cpp
new file mode 100644
index 0000000..5b18bb0
--- /dev/null
+++ b/rivulet.cpp
@@ -0,0 +1,118 @@
+#include <hardware/gpio.h>
+#include <pico/printf.h>
+#include <pico/stdio_usb.h>
+#include <pico/stdlib.h>
+
+constexpr const unsigned int PERIOD_MS = 3000;
+
+enum {
+    PIN_CLOCK,
+
+    PIN_DATA,
+
+    PIN_CS0,
+    PIN_CS1,
+    PIN_CS2,
+    PIN_CS3,
+    PIN_CS4,
+    PIN_CS5,
+    PIN_CS6,
+    PIN_CS7,
+
+    PIN_LED = 25,
+};
+
+constexpr unsigned int MASK(unsigned int pin) { return 1 << pin; }
+
+enum {
+    MASK_CLOCK = MASK(PIN_CLOCK),
+
+    MASK_DATA = MASK(PIN_DATA),
+
+    MASK_CS0 = MASK(PIN_CS0),
+    MASK_CS1 = MASK(PIN_CS1),
+    MASK_CS2 = MASK(PIN_CS2),
+    MASK_CS3 = MASK(PIN_CS3),
+    MASK_CS4 = MASK(PIN_CS4),
+    MASK_CS5 = MASK(PIN_CS5),
+    MASK_CS6 = MASK(PIN_CS6),
+    MASK_CS7 = MASK(PIN_CS7),
+
+    MASK_LED = MASK(PIN_LED),
+
+    MASK_CSALL = MASK_CS0 | MASK_CS1 | MASK_CS2 | MASK_CS3 | MASK_CS4 | MASK_CS5 | MASK_CS6 | MASK_CS7,
+    MASK_IN = MASK_DATA,
+    MASK_OUT = MASK_CLOCK | MASK_CSALL | MASK_LED,
+    MASK_ALL = MASK_IN | MASK_OUT,
+};
+
+unsigned int read_bit() {
+    gpio_set_mask(MASK_CLOCK);
+    sleep_us(1);
+    gpio_clr_mask(MASK_CLOCK);
+    auto bit = gpio_get(PIN_DATA);
+    sleep_us(1);
+    return bit;
+}
+
+unsigned int read_sensor(unsigned int i) {
+    unsigned int cs;
+    switch (i) {
+        case 0: cs = PIN_CS0; break;
+        case 1: cs = PIN_CS1; break;
+        case 2: cs = PIN_CS2; break;
+        case 3: cs = PIN_CS3; break;
+        case 4: cs = PIN_CS4; break;
+        case 5: cs = PIN_CS5; break;
+        case 6: cs = PIN_CS6; break;
+        case 7: cs = PIN_CS7; break;
+        default: return 0;
+    }
+
+    gpio_clr_mask(MASK(cs));
+    sleep_us(1);
+
+    // 3 leading zero bits
+    for (unsigned int i = 0; i < 3; ++i)
+        read_bit();
+
+    // 12 data bits; big endian
+    unsigned int result = 0;
+    for (unsigned int i = 0; i < 12; ++i)
+        result = (result << 1) | read_bit();
+
+    gpio_set_mask(MASK(cs));
+    sleep_us(1);
+
+    return result;
+}
+
+int main() {
+    stdio_usb_init();
+    gpio_init_mask(MASK_ALL);
+    gpio_set_dir_in_masked(MASK_IN);
+    gpio_set_dir_out_masked(MASK_OUT);
+    gpio_set_mask(MASK_CSALL);
+    gpio_clr_mask(MASK_CLOCK | MASK_LED);
+
+    while (true) {
+        if (!stdio_usb_connected()) {
+            sleep_ms(1000);
+            continue;
+        }
+
+        gpio_set_mask(MASK_LED);
+
+        while (stdio_usb_connected()) {
+            printf("[");
+            for (unsigned int i = 0; i < 8; ++i)
+                printf(" %u", read_sensor(i));
+            printf(" ]\n");
+            sleep_ms(PERIOD_MS);
+        }
+
+        gpio_clr_mask(MASK_LED);
+    }
+
+    return 0;
+}
-- 
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