Start beautifying the code

* Split out SPI and display (a little)
* Use more of the common Macros
* Remove wasted bytes from notomono font
* Create a mock "menu"

spi.c

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2019  Max Regan
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "spi.h"
+
+#include "stm32l0xx.h"
+#include "macros.h"
+
+void spi_send_blocking(SPI_TypeDef *spi, const uint8_t *data, size_t len)
+{
+    if (len <= 0) {
+        return;
+    }
+
+    spi->CR1 |= SPI_CR1_SPE;
+
+    for (size_t i = 0; i < len; i++) {
+        while (!(spi->SR & SPI_SR_TXE)) {}
+        spi->DR = data[i];
+    }
+
+    while (!(spi->SR & SPI_SR_TXE)) {}
+
+    // Ensure that NSS is held for long enough to meet the display's thSCS
+    for (int i = 0; i < 4; i++);
+
+    spi->CR1 &= ~SPI_CR1_SPE;
+}