feat: autohold, persistent config (ext flash), a little cleanup? maybe

inc/config.h

@@ -0,0 +1,152 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#define ERASE_PAGE_SIZE 64
+#define CONFIG_MAGIC 0x1234ABCD
+#define CONFIG_VERSION 1
+
+#define MY_ADDR 0
+#define DEFAULT_DMM_ADDR 18  // the HP3478A addr
+
+// Timing Config
+#define USB_DEBOUNCE_CONNECT_MS 50
+#define USB_DEBOUNCE_DISCONNECT_MS 200
+
+#define ENV_SENSOR_READ_INTERVAL_MS 1000
+#define DEFAULT_GPIB_TIMEOUT_MS 1200
+
+// This kind of ass but.. yeah, I don't want to access systick there
+// assume if the PC hasn't read after ~5ms it's stalled
+#define USB_TIMEOUT_TARGET_MS 5
+#define CYCLES_PER_LOOP 50
+#define USB_TIMEOUT_LIMIT \
+  ((FUNCONF_SYSTEM_CORE_CLOCK / 1000 * USB_TIMEOUT_TARGET_MS) / CYCLES_PER_LOOP)
+
+// Menu Animation Timings
+#define MENU_DOT_INTERVAL_MS 500    // Speed of "..." addition
+#define MENU_COMMIT_DELAY_MS 2400   // Time to hold before entering mode
+#define MENU_SUBLAYER_DELAY_MS 500  // Time to "hover" before dots start
+#define MENU_DEBOUNCE_MS 100        // Button press dead-time
+#define MENU_LOCKOUT_MS 1000  // How long to ignore SRQ for after exiting menu
+
+// Polling
+#define POLL_INTERVAL_MS 100        // 10Hz polling when in Passthrough
+#define DMM_RECOVERY_DELAY_MS 1000  // Backoff if DMM vanishes
+
+// Diode sound
+#define DIODE_TH_SHORT 0.050  // Volts (below this = SHORT)
+#define DIODE_TH_OPEN 2.500   // Volts (above this = OPEN/OL)
+#define DIODE_STABLE_MS 20    // wait X ms for voltage to settle
+#define DIODE_CHIRP_MS 50
+
+// PT1000 (DIN 43760 / IEC 751 Standard)
+#define RTD_A 3.9083e-3
+#define RTD_B -5.775e-7
+#define RTD_R0 1000.0
+
+// Thermocouple
+#define CJC_FALLBACK_TEMP 22.0  // used if !app.env_sensor_present
+// this is just cursed but.. yeah, the PCB is near a transformer
+// ideally, the temp should be measured right at the binding posts..
+#define CJC_SELF_HEATING_OFFSET 4.0
+#define TYPE_K_SCALE 24390.24  // 1 / 41uV
+// dBm
+#define DBM_REF_Z 50.0
+// Stats
+#define STATS_CYCLE_TIME_MS 3000  // time per screen (Live -> Avg -> Min...)
+#define STATS_INIT_MIN_VAL 1.0e9
+#define STATS_INIT_MAX_VAL -1.0e9
+
+// Autohold
+#define AUTOHOLD_THRESHOLD 1.0   // deviation % allowed for stability check
+#define AUTOHOLD_CHANGE_REQ 2.0  // % new value must differ by to trigger upd
+// XXX: ideally, we should have different sample requirements for diff ranges
+// we don't need as many counts at N5 range as at N3
+#define AUTOHOLD_STABLE_COUNT 3  // num samples required
+#define AUTOHOLD_MIN_VAL 0.05    // noise floor
+
+#define CONT_DISP_UPDATE_MS 150   // display throttling
+#define CONT_THRESHOLD_OHMS 10.0  // continuity beep threshold
+
+#define REL_STABLE_COUNT 3  // filter depth for Relative NULL
+
+#define BUZZER_CHIRP_HZ 3000
+#define BUZZER_CHIRP_MS 75
+#define BUZZER_CONT_HZ 2500
+
+typedef struct {
+  uint32_t magic;
+  uint32_t version;
+
+  // addressing
+  uint8_t my_addr;      // controller
+  uint8_t dmm_addr;     // hp3478a
+  uint8_t target_addr;  // target
+
+  uint8_t eot_char;
+  uint8_t eot_enable;
+  uint8_t eoi_assert;
+  uint8_t eos_mode;
+  uint8_t eor_mode;
+  uint8_t auto_read;
+  uint8_t padding;  // align
+
+  // timings (ms)
+  uint32_t gpib_timeout_ms;
+  uint32_t poll_interval_ms;
+  uint32_t env_sensor_read_interval_ms;
+  uint32_t dmm_recovery_delay_ms;
+  uint32_t usb_debounce_connect_ms;
+  uint32_t usb_debounce_disconnect_ms;
+  uint32_t usb_timeout_target_ms;
+
+  // timings
+  uint32_t menu_dot_interval_ms;
+  uint32_t menu_commit_delay_ms;
+  uint32_t menu_sublayer_delay_ms;
+  uint32_t menu_debounce_ms;
+  uint32_t menu_lockout_ms;
+  uint32_t stats_cycle_time_ms;
+  uint32_t cont_disp_update_ms;
+  uint32_t diode_stable_ms;
+
+  // buzzer
+  uint32_t buzzer_chirp_hz;
+  uint32_t buzzer_chirp_ms;
+  uint32_t buzzer_cont_hz;
+
+  // math & cal
+  double rtd_a;
+  double rtd_b;
+  double rtd_r0;
+  double cjc_fallback_temp;
+  double cjc_self_heating_offset;
+  double type_k_scale;
+  double dbm_ref_z;
+  double diode_th_short;
+  double diode_th_open;
+
+  // thresholds
+  double autohold_threshold;
+  double autohold_change_req;
+  double autohold_min_val;
+  double cont_threshold_ohms;
+
+  // logic counts
+  uint32_t autohold_stable_count;
+  uint32_t rel_stable_count;
+
+} fw_config_t;
+
+typedef enum { CFG_TYPE_UINT8, CFG_TYPE_UINT32, CFG_TYPE_DOUBLE } cfg_type_t;
+
+typedef struct {
+  const char* name;
+  size_t offset;
+  cfg_type_t type;
+} cfg_field_t;
+
+#endif  // CONFIG_H

inc/systick.h

@@ -9,11 +9,7 @@
 #define SYSTICK_ONE_MILLISECOND ((uint32_t)FUNCONF_SYSTEM_CORE_CLOCK / 1000)
 #define SYSTICK_ONE_MICROSECOND ((uint32_t)FUNCONF_SYSTEM_CORE_CLOCK / 1000000)
 
-extern volatile uint32_t systick_millis;
-
 #define millis() (systick_millis)
 #define micros() (SysTick->CNT / SYSTICK_ONE_MICROSECOND)
 
-void systick_init(void);
-
 #endif  // SYSTICK_H

inc/usb_config.h

@@ -22,10 +22,10 @@
 
 #define FUSB_USB_VID 0x1209
 #define FUSB_USB_PID 0x3478
-#define FUSB_USB_REV 0x0110
+#define FUSB_USB_REV 0x0120
 #define FUSB_STR_MANUFACTURER u"Open Source GPIB"
 #define FUSB_STR_PRODUCT      u"HP3478A Internal Adapter"
-#define FUSB_STR_SERIAL       u"3478A-USB-110"
+#define FUSB_STR_SERIAL       u"3478A-USB-120"
 
 //Taken from http://www.usbmadesimple.co.uk/ums_ms_desc_dev.htm
 static const uint8_t device_descriptor[] = {