1 files changed, 109 insertions, 0 deletions
diff --git a/src/stm32f1/adc.c b/src/stm32f1/adc.c
new file mode 100644
index 00000000..2fe4977e
--- /dev/null
+++ b/src/stm32f1/adc.c
@@ -0,0 +1,109 @@
+// ADC functions on STM32F1
+//
+// Copyright (C) 2018 Grigori Goronzy <greg@kinoho.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stdbool.h> // bool
+#include "board/io.h" // readb
+#include "command.h" // shutdown
+#include "compiler.h" // ARRAY_SIZE
+#include "gpio.h" // gpio_adc_setup
+#include "internal.h" // GPIO
+#include "stm32f1xx_ll_adc.h" // LL_ADC_REG_ReadConversionData12
+#include "stm32f1xx_ll_gpio.h" // LL_GPIO_SetPinMode
+#include "sched.h" // sched_shutdown
+
+DECL_CONSTANT(ADC_MAX, 4095);
+
+#define ADC_DELAY (240 * 8)
+
+static bool adc_busy;
+static uint32_t adc_current_channel;
+
+static const uint8_t adc_pins[] = {
+    GPIO('A', 0), GPIO('A', 1), GPIO('A', 2), GPIO('A', 3),
+    GPIO('A', 4), GPIO('A', 5), GPIO('A', 6), GPIO('A', 7),
+    GPIO('B', 0), GPIO('B', 1), GPIO('C', 0), GPIO('C', 1),
+    GPIO('C', 2), GPIO('C', 3), GPIO('C', 4), GPIO('C', 5)
+};
+
+static const uint32_t adc_channels[] = {
+    LL_ADC_CHANNEL_0,
+    LL_ADC_CHANNEL_1,
+    LL_ADC_CHANNEL_2,
+    LL_ADC_CHANNEL_3,
+    LL_ADC_CHANNEL_4,
+    LL_ADC_CHANNEL_5,
+    LL_ADC_CHANNEL_6,
+    LL_ADC_CHANNEL_7,
+    LL_ADC_CHANNEL_8,
+    LL_ADC_CHANNEL_9,
+    LL_ADC_CHANNEL_10,
+    LL_ADC_CHANNEL_11,
+    LL_ADC_CHANNEL_12,
+    LL_ADC_CHANNEL_13,
+    LL_ADC_CHANNEL_14,
+    LL_ADC_CHANNEL_15,
+};
+
+struct gpio_adc
+gpio_adc_setup(uint8_t pin)
+{
+    // Find pin in adc_pins table
+    int chan;
+    for (chan=0; ; chan++) {
+        if (chan >= ARRAY_SIZE(adc_pins))
+            shutdown("Not a valid ADC pin");
+        if (adc_pins[chan] == pin)
+            break;
+    }
+
+    GPIO_TypeDef *regs = digital_regs[GPIO2PORT(pin)];
+    uint32_t bit = digital_pins[pin % 16];
+    LL_GPIO_SetPinMode(regs, bit, LL_GPIO_MODE_ANALOG);
+
+    return (struct gpio_adc){ .bit = adc_channels[chan] };
+}
+
+// Try to sample a value. Returns zero if sample ready, otherwise
+// returns the number of clock ticks the caller should wait before
+// retrying this function.
+uint32_t
+gpio_adc_sample(struct gpio_adc g)
+{
+    /* ADC not busy, start conversion */
+    if (!readb(&adc_busy)) {
+        LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_1, g.bit);
+        LL_ADC_SetChannelSamplingTime(ADC1, g.bit, LL_ADC_SAMPLINGTIME_239CYCLES_5);
+        LL_ADC_REG_StartConversionSWStart(ADC1);
+        adc_busy = true;
+        adc_current_channel = g.bit;
+        return ADC_DELAY;
+    /* ADC finished conversion for this channel */
+    } else if (LL_ADC_IsActiveFlag_EOS(ADC1) &&
+               readl(&adc_current_channel) == g.bit) {
+        LL_ADC_ClearFlag_EOS(ADC1);
+        adc_busy = false;
+        return 0;
+    }
+    /* Wants to sample another channel, or not finished yet */
+    return ADC_DELAY;
+}
+
+// Read a value; use only after gpio_adc_sample() returns zero
+uint16_t
+gpio_adc_read(struct gpio_adc g)
+{
+    return LL_ADC_REG_ReadConversionData12(ADC1);
+}
+
+// Cancel a sample that may have been started with gpio_adc_sample()
+void
+gpio_adc_cancel_sample(struct gpio_adc g)
+{
+    if (readb(&adc_busy) && readl(&adc_current_channel) == g.bit) {
+        adc_busy = false;
+        LL_ADC_ClearFlag_EOS(ADC1);
+    }
+}