lpc176x: Move ADC code to new adc.c file

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 96 insertions, 0 deletions

diff --git a/src/lpc176x/adc.c b/src/lpc176x/adc.c
new file mode 100644
index 00000000..d7071896
--- /dev/null
+++ b/src/lpc176x/adc.c
@@ -0,0 +1,96 @@
+// Analog to digital support on lpc176x
+//
+// Copyright (C) 2018-2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "LPC17xx.h" // LPC_PINCON
+#include "autoconf.h" // CONFIG_CLOCK_FREQ
+#include "board/misc.h" // timer_from_us
+#include "command.h" // shutdown
+#include "gpio.h" // gpio_adc_setup
+#include "internal.h" // gpio_peripheral
+#include "sched.h" // sched_shutdown
+
+static const uint8_t adc_pins[] = {
+    GPIO(0, 23), GPIO(0, 24), GPIO(0, 25), GPIO(0, 26),
+    GPIO(1, 30), GPIO(1, 31), GPIO(0, 3), GPIO(0, 2),
+};
+
+static const uint8_t adc_pin_funcs[] = {
+    1, 1, 1, 1, 3, 3, 2, 2
+};
+
+#define ADC_FREQ_MAX 13000000
+DECL_CONSTANT(ADC_MAX, 4095);
+
+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;
+    }
+
+    uint32_t prescal = DIV_ROUND_UP(CONFIG_CLOCK_FREQ*4, ADC_FREQ_MAX) - 1;
+    uint32_t adcr = (1<<21) | ((prescal & 0xff) << 8);
+    if (!(LPC_SC->PCONP & (1<<PCLK_ADC))) {
+        // Power up ADC
+        enable_peripheral_clock(PCLK_ADC);
+        LPC_ADC->ADCR = adcr;
+    }
+
+    gpio_peripheral(GPIO2PORT(pin), pin % 32, adc_pin_funcs[chan], 0);
+
+    return (struct gpio_adc){ .cmd = adcr | (1 << chan) | (1 << 24) };
+}
+
+static uint32_t adc_status;
+
+// 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)
+{
+    uint32_t status = adc_status;
+    if (status == g.cmd) {
+        // Sample already underway - check if it is ready
+        uint32_t val = LPC_ADC->ADGDR;
+        if (val & (1<<31))
+            // Sample ready
+            return 0;
+        goto need_delay;
+    }
+    if (status)
+        // ADC busy on some other channel
+        goto need_delay;
+
+    // Start new sample
+    adc_status = g.cmd;
+    LPC_ADC->ADCR = g.cmd;
+
+need_delay:
+    return (65 * DIV_ROUND_UP(CONFIG_CLOCK_FREQ*4, ADC_FREQ_MAX)
+            + timer_from_us(10));
+}
+
+// Read a value; use only after gpio_adc_sample() returns zero
+uint16_t
+gpio_adc_read(struct gpio_adc g)
+{
+    adc_status = 0;
+    return (LPC_ADC->ADGDR >> 4) & 0x0fff;
+}
+
+// Cancel a sample that may have been started with gpio_adc_sample()
+void
+gpio_adc_cancel_sample(struct gpio_adc g)
+{
+    if (adc_status == g.cmd)
+        adc_status = 0;
+}