Diff: Hx711.cpp

Revision:

1:392a3fb6d177

diff -r 5d67331a6e7e -r 392a3fb6d177 Hx711.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Hx711.cpp	Fri Sep 03 04:51:59 2021 +0000
@@ -0,0 +1,77 @@
+#include "mbed.h"
+#include "Hx711.h"
+
+void Hx711::set_gain(uint8_t gain) {
+    switch (gain) {
+        case 128:       // channel A, gain factor 128
+            gain_ = 1;
+            break;
+        case 64:        // channel A, gain factor 64
+            gain_ = 3;
+            break;
+        case 32:        // channel B, gain factor 32
+            gain_ = 2;
+            break;
+    }
+
+    sck_.write(LOW);
+    read();
+}
+
+uint32_t Hx711::readRaw() {
+    // wait for the chip to become ready
+    // TODO: this is not ideal; the programm will hang if the chip never
+    // becomes ready...
+    while (!is_ready());
+
+    uint32_t value = 0;
+    uint8_t data[3] = { 0 };
+    uint8_t filler = 0x00;
+
+    // pulse the clock pin 24 times to read the data
+    data[2] = shiftInMsbFirst();
+    data[1] = shiftInMsbFirst();
+    data[0] = shiftInMsbFirst();
+
+    // set the channel and the gain factor for the next reading using the clock pin
+    for (unsigned int i = 0; i < gain_; i++) {
+        sck_.write(HIGH);
+        sck_.write(LOW);
+    }
+
+    // Datasheet indicates the value is returned as a two's complement value
+    // Flip all the bits
+    data[2] = ~data[2];
+    data[1] = ~data[1];
+    data[0] = ~data[0];
+
+    // Replicate the most significant bit to pad out a 32-bit signed integer
+    if ( data[2] & 0x80 ) {
+        filler = 0xFF;
+    } else if ((0x7F == data[2]) && (0xFF == data[1]) && (0xFF == data[0])) {
+        filler = 0xFF;
+    } else {
+        filler = 0x00;
+    }
+
+    // Construct a 32-bit signed integer
+    value = ( static_cast<uint32_t>(filler)  << 24
+            | static_cast<uint32_t>(data[2]) << 16
+            | static_cast<uint32_t>(data[1]) << 8
+            | static_cast<uint32_t>(data[0]) );
+
+    // ... and add 1
+    return static_cast<int>(++value);
+}
+
+
+uint8_t Hx711::shiftInMsbFirst() {
+    uint8_t value = 0;
+
+    for (uint8_t i = 0; i < 8; ++i) {
+        sck_.write(HIGH);
+        value |= dt_.read() << (7 - i);
+        sck_.write(LOW);
+    }
+    return value;
+}