Fix LTC2400 readout

4 files changed, 46 insertions, 22 deletions

diff --git a/sw/Makefile b/sw/Makefile
index 259583d..931455a 100644
--- a/sw/Makefile
+++ b/sw/Makefile
@@ -119,7 +119,7 @@ clean:
 # Send to device
 program: $(APP_HEX)
 	$(SIZE) -C $(BUILD_DIR)/$(APP_ELF)
-	$(AVRDUDE) $(AVRDUDE_FLAGS) -c $(PROG) -P $(AVRDUDE_DEV) -p $(AVRDUDE_PART) -U flash:w:$(BUILD_DIR)/$(APP_HEX) -v
+	$(AVRDUDE) $(AVRDUDE_FLAGS) -c $(PROG) -P $(AVRDUDE_DEV) -p $(AVRDUDE_PART) -U flash:w:$(BUILD_DIR)/$(APP_HEX) -v -B 8
 
 fuse:
 	$(AVRDUDE) $(AVRDUDE_FLAGS) -c $(PROG) -P $(AVRDUDE_DEV) -p $(AVRDUDE_PART) -U lfuse:w:0x7e:m -U hfuse:w:0xd9:m -U efuse:w:0xfc:m -v
diff --git a/sw/ltc2400.cpp b/sw/ltc2400.cpp
index a221029..f0cfa13 100644
--- a/sw/ltc2400.cpp
+++ b/sw/ltc2400.cpp
@@ -66,6 +66,7 @@
 
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include <util/delay.h>
 #include "ltc2400.h"
 
 static void cs_low()
@@ -82,10 +83,9 @@ static void cs_high()
     sei();
 }
 
-void ltc2400_init()
+static void spi_en()
 {
     cli();
-
     // Set SPI Enable and Master mode,
     // bit order=MSB first (DORD=0),
     // SPI mode=0 (CPOL=0, CPHA=0)
@@ -103,31 +103,46 @@ void ltc2400_init()
     //   1    0     1   fosc/64
     //   1    1     1   fosc/128
     //
-    // Set SPR1 for /32
-    SPCR = _BV(SPE) | _BV(MSTR) | _BV(SPR1);
+    // Set SPR0 for /8
+    SPCR = _BV(SPE) | _BV(MSTR) | _BV(SPR0);
     SPSR = 0; // clear SPI2X
+    sei();
+}
 
+static void spi_dis()
+{
+    cli();
+    PORTB &= ~PINB_SPI_SCK;
+    SPCR = _BV(MSTR) | _BV(SPR1);
     sei();
 }
 
-bool ltc2400_conversion_ready()
+void ltc2400_init()
 {
-    return true;
-#warning "Clarify usage of SS"
+    cli();
+    PORTB |= PINB_SPI_LTC_CSn;
+    // Ensure CLK is low so that the device doesn't enter internal SCK mode
+    PORTB &= ~PINB_SPI_SCK;
+    sei();
+}
 
+bool ltc2400_conversion_ready()
+{
     cs_low();
-    // EOC == 0 means conversion is complete and device in sleep mode
-    const int eoc = (PORTB & PINB_SPI_MISO) ? 0 : 1;
 
-    cs_high();
+    _delay_us(100);
 
-    return eoc;
+    // EOC == 0 means conversion is complete and device in sleep mode
+    return not (PINB & PINB_SPI_MISO);
 }
 
-float ltc2400_get_conversion_result(bool& dmy_fault, bool& exr_fault, uint32_t& raw_value)
+double ltc2400_get_conversion_result(bool& dmy_fault, bool& exr_fault, uint32_t& raw_value)
 {
+    spi_en();
     cs_low();
 
+    _delay_us(100);
+
     uint8_t data[4] = {};
 
     for (int i = 0; i < 4; i++) {
@@ -137,6 +152,7 @@ float ltc2400_get_conversion_result(bool& dmy_fault, bool& exr_fault, uint32_t&
         data[i] = SPDR;
     }
 
+    spi_dis();
     cs_high();
 
     raw_value =
@@ -152,6 +168,6 @@ float ltc2400_get_conversion_result(bool& dmy_fault, bool& exr_fault, uint32_t&
     const uint32_t adc_value = (raw_value >> 4) & 0x00FFFFFF;
 
     // Convert ADC value to voltage
-    return ((float)adc_value) / ((float)0x00FFFFFF) / 5.0f;
+    return (double)adc_value / ((double)0x00FFFFFF / 5.0f);
 }
 
diff --git a/sw/ltc2400.h b/sw/ltc2400.h
index d46a24f..05204dd 100644
--- a/sw/ltc2400.h
+++ b/sw/ltc2400.h
@@ -33,4 +33,4 @@ void ltc2400_init();
 
 bool ltc2400_conversion_ready();
 
-float ltc2400_get_conversion_result(bool& dmy_fault, bool& exr_fault, uint32_t& raw_value);
+double ltc2400_get_conversion_result(bool& dmy_fault, bool& exr_fault, uint32_t& raw_value);
diff --git a/sw/main.cpp b/sw/main.cpp
index f929c84..94a444a 100644
--- a/sw/main.cpp
+++ b/sw/main.cpp
@@ -46,7 +46,7 @@ extern "C" {
 // UART endline is usually CR LF
 #define ENDL "\r\n"
 
-constexpr double R_SHUNT = 5e-3; // Ohm
+constexpr double R_SHUNT = 1e-3; // Ohm
 
 /* Capacity counters and thresholds, in As (= Coulombs)
  *
@@ -145,6 +145,7 @@ enum class error_type_t {
     EEPROM_READ_WARNING,
     EEPROM_READ_ERROR,
     EEPROM_WRITE_ERROR,
+    LTC2400_NOT_READY,
     LTC2400_DMY_BIT_FAULT,
     LTC2400_EXTENDED_RANGE_ERROR,
     RELAY_NOT_SET,
@@ -250,7 +251,7 @@ static void handle_thresholds(const timer_t& time_now)
     previous_capacity = current_capacity;
 }
 
-static char timestamp_buf[24];
+static char timestamp_buf[32];
 static void send_message(const char *message)
 {
     snprintf(timestamp_buf, sizeof(timestamp_buf), "TEXT,%ld,", system_timer.get_seconds_atomic());
@@ -289,6 +290,9 @@ static void flag_error(const error_type_t e)
         case error_type_t::EEPROM_WRITE_ERROR:
             uart_puts_P("EEPRON write error" ENDL);
             break;
+        case error_type_t::LTC2400_NOT_READY:
+            uart_puts_P("LTC2400 not ready" ENDL);
+            break;
         case error_type_t::LTC2400_DMY_BIT_FAULT:
             uart_puts_P("LTC2400 DMY bit error" ENDL);
             break;
@@ -405,8 +409,7 @@ int main()
             store_capacity_to_eeprom();
         }
 #endif
-
-        const auto ltc2400_measure_interval = timer_t{0, 100000uL};
+        const auto ltc2400_measure_interval = timer_t{0, 200000uL};
         if (last_ltc2400_measure + ltc2400_measure_interval < time_now) {
             last_ltc2400_measure += ltc2400_measure_interval;
 
@@ -414,7 +417,7 @@ int main()
                 bool dmy_fault = false;
                 bool exr_fault = false;
                 uint32_t adc_value = 0;
-                const float adc_voltage = ltc2400_get_conversion_result(dmy_fault, exr_fault, adc_value);
+                const double adc_voltage = ltc2400_get_conversion_result(dmy_fault, exr_fault, adc_value);
 
                 if (dmy_fault) {
                     flag_error(error_type_t::LTC2400_DMY_BIT_FAULT);
@@ -426,9 +429,11 @@ int main()
 
                 /* Vout - 2.5V = Ishunt * Rshunt * 20 */
                 const double i_shunt = (adc_voltage - 2.5) / (20.0 * R_SHUNT);
-                capacity_accum += i_shunt * TIMER_TICK_INTERVAL;
+                capacity_accum += i_shunt * ltc2400_measure_interval.microsecs_ * 1e-6;
 
-                snprintf(timestamp_buf, sizeof(timestamp_buf), "DBG,%ld mA" ENDL, lrint(i_shunt * 1000.0));
+                snprintf(timestamp_buf, sizeof(timestamp_buf), "DBG,%ldmV,%ldmA" ENDL,
+                        lrint(adc_voltage * 1e3),
+                        lrint(i_shunt * 1e3));
                 uart_puts(timestamp_buf);
 
                 if (capacity_accum < 0) { capacity_accum = 0; }
@@ -436,6 +441,9 @@ int main()
 
                 current_capacity = lrint(capacity_accum);
             }
+            else {
+                flag_error(error_type_t::LTC2400_NOT_READY);
+            }
         }
 
         constexpr auto threshold_calculation_interval_s = 4;