fewer magic numbers

.vscode/settings.json

@@ -35,5 +35,8 @@
     "raspberry-pi-pico.cmakeAutoConfigure": true,
     "raspberry-pi-pico.useCmakeTools": false,
     "raspberry-pi-pico.cmakePath": "${HOME}/.pico-sdk/cmake/v3.28.6/bin/cmake",
-    "raspberry-pi-pico.ninjaPath": "${HOME}/.pico-sdk/ninja/v1.12.1/ninja"
+    "raspberry-pi-pico.ninjaPath": "${HOME}/.pico-sdk/ninja/v1.12.1/ninja",
+    "files.associations": {
+        "cstdint": "c"
+    }
 }

include/hx711_spi_master.h

@@ -32,6 +32,8 @@ extern "C" {
 #endif
 
 #define HX711_SPI_BAUD_RATE 1000000
+#define HX711_SPI_COMMAND_BITS 3
+#define HX711_SPI_DATA_BITS 5
 
 typedef enum {
     hx711_spi_command_none = 0,
@@ -146,6 +148,82 @@ uint8_t hx711_spi_gain_to_spi_gain(
 hx711_gain_t hx711_spi_spi_gain_to_gain(
     const uint8_t spi_gain);
 
+/**
+ * @brief Combine command and data into a byte for an
+ * SPI transfer.
+ * 
+ * @param cmd 
+ * @param data 
+ * @return uint8_t 
+ */
+uint8_t hx711_spi_create_xfer(
+    const hx711_spi_command_t cmd,
+    const uint8_t data);
+
+/**
+ * @brief Extract command and data from the byte
+ * obtained via SPI transfer.
+ * 
+ * @param inbyte 
+ * @param cmd 
+ * @param data 
+ */
+void hx711_spi_parse_xfer(
+    const uint8_t inbyte,
+    hx711_spi_command_t* const cmd,
+    uint8_t* const data);
+
+/**
+ * @brief Check if command is a valid command.
+ * 
+ * @param cmd 
+ * @return true 
+ * @return false 
+ */
+bool hx711_spi_is_command_valid(
+    const hx711_spi_command_t cmd);
+
+/**
+ * @brief Extract command from transfer data.
+ * 
+ * @param xfer 
+ * @return hx711_spi_command_t 
+ */
+hx711_spi_command_t hx711_spi_get_command_from_xfer(
+    const uint8_t xfer);
+
+/**
+ * @brief Insert command into transfer data.
+ * 
+ * @param cmd 
+ * @param xfer 
+ * @return uint8_t 
+ */
+uint8_t hx711_spi_put_command_in_xfer(
+    const hx711_spi_command_t cmd,
+    const uint8_t xfer);
+
+/**
+ * @brief Extract arbitrary data from transfer
+ * data.
+ * 
+ * @param xfer 
+ * @return uint8_t 
+ */
+uint8_t hx711_spi_get_data_from_xfer(
+    const uint8_t xfer);
+
+/**
+ * @brief Put arbitrary data into transfer data.
+ * 
+ * @param data 
+ * @param xfer 
+ * @return uint8_t 
+ */
+uint8_t hx711_spi_put_data_in_xfer(
+    const uint8_t data,
+    uint8_t const xfer);
+
 #ifdef __cplusplus
 }
 #endif

include/hx711_spi_slave.h

@@ -62,12 +62,28 @@ typedef struct {
 
 } hx711_spi_slave_config_t;
 
+/**
+ * @brief Initialise SPI slave device.
+ * 
+ * @param hx_spi 
+ * @param hx_spi_config 
+ */
 void hx711_spi_slave_init(
     hx711_spi_slave_t* const hx_spi,
     const hx711_spi_slave_config_t * const hx_spi_config);
 
+/**
+ * @brief Stop SPI communication.
+ * 
+ * @param hx_spi 
+ */
 void hx711_spi_slave_close(hx711_spi_slave_t* const hx_spi);
 
+/**
+ * @brief Listen for incoming SPI messages and respond.
+ * 
+ * @param hx_spi 
+ */
 void hx711_spi_slave_listen(hx711_spi_slave_t* const hx_spi);
 
 #ifdef __cplusplus

src/hx711_spi_master.c

@@ -1,6 +1,6 @@
 // MIT License
 // 
-// Copyright (c) 2023 Daniel Robertson
+// Copyright (c) 2024 Daniel Robertson
 // 
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -77,14 +77,14 @@ void hx711_spi_master_set_gain(
         assert(hx_spi->_spi != NULL);
         assert(hx711_is_gain_valid(gain));
 
-        const uint8_t data = 
-            (hx711_spi_gain_to_spi_gain(gain) << 3) |
-            (uint8_t)hx711_spi_command_set_gain;
+        const uint8_t xfer = hx711_spi_create_xfer(
+            hx711_spi_command_set_gain,
+            hx711_spi_gain_to_spi_gain(gain));
 
         spi_write_blocking(
             hx_spi->_spi,
-            &data,
-            sizeof(data));
+            &xfer,
+            sizeof(xfer));
 
 }
 
@@ -114,15 +114,15 @@ void hx711_spi_master_power_up(
         assert(hx_spi->_spi != NULL);
         assert(hx711_is_gain_valid(gain));
 
-        const uint8_t data = 
-            (hx711_spi_gain_to_spi_gain(gain) << 3) |
-            (uint8_t)hx711_spi_command_set_gain;
+        const uint8_t xfer = hx711_spi_create_xfer(
+            hx711_spi_command_power_up,
+            hx711_spi_gain_to_spi_gain(gain));
 
         spi_write_read_blocking(
             hx_spi->_spi,
-            &data,
+            &xfer,
             NULL,
-            sizeof(data));
+            sizeof(xfer));
 
 }
 
@@ -132,12 +132,13 @@ void hx711_spi_master_power_down(
         assert(hx_spi != NULL);
         assert(hx_spi->_spi != NULL);
 
-        const uint8_t cmd = (uint8_t)hx711_spi_command_power_down;
+        const uint8_t xfer = hx711_spi_create_xfer(
+            hx711_spi_command_power_down, 0);
 
         spi_write_blocking(
             hx_spi->_spi,
-            &cmd,
-            sizeof(cmd));
+            &xfer,
+            sizeof(xfer));
 
 }
 
@@ -156,3 +157,61 @@ hx711_gain_t hx711_spi_spi_gain_to_gain(const uint8_t spi_gain) {
     assert(hx711_is_gain_valid(gain));
     return gain;
 }
+
+uint8_t hx711_spi_create_xfer(
+    const hx711_spi_command_t cmd,
+    const uint8_t data) {
+        uint8_t xfer = 0;
+        xfer = hx711_spi_put_command_in_xfer(cmd, xfer);
+        xfer = hx711_spi_put_data_in_xfer(data, xfer);
+        return xfer;
+}
+
+void hx711_spi_parse_xfer(
+    const uint8_t inbyte,
+    hx711_spi_command_t* const cmd,
+    uint8_t* const data) {
+
+        assert(cmd != NULL);
+
+        *cmd = hx711_spi_get_command_from_xfer(inbyte);
+        assert(hx711_spi_is_command_valid(*cmd));
+
+        if(data != NULL) {
+            *data = hx711_spi_get_data_from_xfer(inbyte);
+        }
+
+}
+
+bool hx711_spi_is_command_valid(
+    const hx711_spi_command_t cmd) {
+        return (uint8_t)cmd <= hx711_spi_command_get_value;
+}
+
+hx711_spi_command_t hx711_spi_get_command_from_xfer(
+    const uint8_t data) {
+        const hx711_spi_command_t cmd = 
+            (hx711_spi_command_t)(data & ((1 << HX711_SPI_COMMAND_BITS) - 1));
+        assert(hx711_spi_is_command_valid(cmd));
+        return cmd;
+}
+
+uint8_t hx711_spi_put_command_in_xfer(
+    const hx711_spi_command_t cmd,
+    const uint8_t xfer) {
+        assert(hx711_spi_is_command_valid(cmd));
+        const uint8_t mask = (1 << HX711_SPI_COMMAND_BITS) - 1;
+        const uint8_t cmdbits = ((uint8_t)cmd) & mask;
+        return xfer | cmdbits;
+}
+
+uint8_t hx711_spi_get_data_from_xfer(
+    const uint8_t xfer) {
+        return xfer >> HX711_SPI_COMMAND_BITS;
+}
+
+uint8_t hx711_spi_put_data_in_xfer(
+    const uint8_t data,
+    const uint8_t xfer) {
+        return xfer | (data << HX711_SPI_COMMAND_BITS);
+}

src/hx711_spi_slave.c

@@ -70,36 +70,48 @@ void hx711_spi_slave_close(hx711_spi_slave_t* const hx_spi) {
 
 void hx711_spi_slave_listen(hx711_spi_slave_t* const hx_spi) {
 
+    uint8_t xfer;
     hx711_spi_command_t cmd;
     uint8_t data;
     hx711_gain_t gain;
-    int32_t out;
+    int32_t val;
 
     while(true) {
 
+        // read one byte containing command
         spi_read_blocking(
             hx_spi->_spi,
-            hx711_spi_command_none,
-            &data,
-            sizeof(data));
+            0,
+            &xfer,
+            sizeof(xfer));
 
-        cmd = (hx711_spi_command_t)(data & 0b00000111);
-        data = data >> 5;
+        // parse the xfer into cmd and data
+        hx711_spi_parse_xfer(
+            xfer,
+            &cmd,
+            &data);
 
         switch(cmd) {
+
             default:
             case hx711_spi_command_get_value:
-                out = hx711_get_value(hx_spi->_hx);
-                spi_write_blocking(hx_spi->_spi, (uint8_t*)&out, sizeof(out));
+                val = hx711_get_value(hx_spi->_hx);
+                spi_write_blocking(
+                    hx_spi->_spi,
+                    (uint8_t*)&val,
+                    sizeof(val));
                 break;
+
             case hx711_spi_command_set_gain:
                 gain = hx711_spi_spi_gain_to_gain(data);
                 hx711_set_gain(hx_spi->_hx, gain);
                 break;
+
             case hx711_spi_command_power_up:
                 gain = hx711_spi_spi_gain_to_gain(data);
                 hx711_power_up(hx_spi->_hx, gain);
                 break;
+
             case hx711_spi_command_power_down:
                 hx711_power_down(hx_spi->_hx);
                 break;