ADC voltage: battcheck 3 digits, fixed t1616, switched back to 8-bit internal volt unit

Before this branch, `voltage` was 6 bits: Volts * 10
A couple patches ago, I upgraded it to 16 bits: 65535 * Volts / 10.24
That costs too much extra ROM on attiny85 though, for extra precision
it doesn't even use... so I switched back to an 8-bit value.  It's still
more precise than before though: Volts * 40
... and battcheck displays an extra digit now, on devices with ROM for it.
... and battcheck waits a second to get a more accurate measurement
    before displaying the first value.  It has *much* less variation
    between first and later readings now.

Also:
- got t1616 builds working again (tested fc13 and thefreeman-boost-fwaa)
- upgraded t1616 voltage and temp to 12-bit (10 bits + 4x oversampling)
- removed expensive temp conversion from t1616 ADC interrupt
- recalibrated t1616 bogomips again; runs faster after interrupt fix
- increased t1616 internal VDD measurement resolution by 36% (1.5V Vref, not 1.1V)
- fixed sloppy setting of Vref bits

I still need to test / update other t1616 builds,
and fix all the t85 + t1634 code and build targets.

2 files changed, 11 insertions, 11 deletions

diff --git a/hw/thefreeman/avr32dd20-devkit/hwdef.c b/hw/thefreeman/avr32dd20-devkit/hwdef.c
index 133baca..3e5dd79 100644
--- a/hw/thefreeman/avr32dd20-devkit/hwdef.c
+++ b/hw/thefreeman/avr32dd20-devkit/hwdef.c
@@ -104,15 +104,15 @@ bool gradual_tick_main(uint8_t gt) {
 }
 
 
-uint16_t voltage_raw2cooked(uint16_t measurement) {
-    // In : 65535 * BATTLVL pin / 1.024 Vref
-    // Out: 65535 * (Vbat / 10) / 1.024V  (i.e. FSM Volt units)
+uint8_t voltage_raw2cooked(uint16_t measurement) {
+    // In : 65535 * BATTLVL / 1.024V
+    // Out: uint8_t: Vbat * 40
     // BATTLVL = Vbat * (100.0/(330+100)) = Vbat / 4.3
-    // So, Out = In * 4.3 / 10.24
-    // (plus 1.5% based on measured hardware)
-    // (plus a fudge factor of +0.04V to round up to nearest 1/10th Volt)
-    uint16_t result = ((uint32_t)measurement * 436 / 1024)
-                    + (65535 * 4 / 1024);
+    // So, Out = In * 4.3 / 1600
+    // (plus a bit of fudging to fix the slope and offset,
+    //  based on measuring actual hardware)
+    uint8_t result = (uint32_t)(measurement + (65535 * 4 / 1024))
+                     * 43 / 16128;
     return result;
 }
 
diff --git a/hw/thefreeman/avr32dd20-devkit/hwdef.h b/hw/thefreeman/avr32dd20-devkit/hwdef.h
index 7e1ad3d..a5b37a9 100644
--- a/hw/thefreeman/avr32dd20-devkit/hwdef.h
+++ b/hw/thefreeman/avr32dd20-devkit/hwdef.h
@@ -111,11 +111,11 @@ enum CHANNEL_MODES {
 // AVR datasheet table 3.1 I/O Multiplexing, PA6 ADC0 = AIN26
 #define USE_VOLTAGE_DIVIDER    // use a dedicated pin, not VCC, because VCC input is regulated
 #define ADMUX_VOLTAGE_DIVIDER  ADC_MUXPOS_AIN26_gc
-#define DUAL_VOLTAGE_FLOOR     21 // for AA/14500 boost drivers, don't indicate low voltage if below this level
-#define DUAL_VOLTAGE_LOW_LOW   7  // the lower voltage range's danger zone 0.7 volts (NiMH)
+#define DUAL_VOLTAGE_FLOOR     (4*21) // for AA/14500 boost drivers, don't indicate low voltage if below this level
+#define DUAL_VOLTAGE_LOW_LOW   (4*7)  // the lower voltage range's danger zone 0.7 volts (NiMH)
 // convert BATT LVL pin readings to FSM volt units
 #undef voltage_raw2cooked
-uint16_t voltage_raw2cooked(uint16_t measurement);
+uint8_t voltage_raw2cooked(uint16_t measurement);
 
 
 // average drop across diode on this hardware