Fix recover from overvoltage/undervoltage state in bms_bq769x0.c (#18)

BMS with BQ76930 did not recover from state "overvoltage" or "undervoltage"
and needed a reset to enable CHG/DSG MOSFETs again.

The SYS_STAT register should be checked each time as an alert interrupt
is only generated once if the error persists. (ALERT pin stays high)

Also fixing MOSFET "switch on" to use ov_reset and uv_reset.

Fixes #19

src/bq769x0/bms_bq769x0.c

@@ -40,6 +40,7 @@ void bms_update(BmsConfig *conf, BmsStatus *status)
     bms_read_current(conf, status);
     bms_read_temperatures(conf, status);
     bms_check_cell_temp(conf, status);      // bq769x0 doesn't support temperature settings
+    bms_update_error_flags(conf, status);
     bms_apply_balancing(conf, status);
 }
 
@@ -516,15 +517,15 @@ void bms_handle_errors(BmsConfig *conf, BmsStatus *status)
     static uint32_t sec_since_error = 0;
 
     // ToDo: Handle also temperature and chg errors (incl. temp hysteresis)
+    SYS_STAT_Type sys_stat;
+    sys_stat.byte = bq769x0_read_byte(BQ769X0_SYS_STAT);
+    error_status = sys_stat.byte;
 
     if (!bq769x0_alert_flag() && error_status == 0) {
         return;
     }
     else {
 
-        SYS_STAT_Type sys_stat;
-        sys_stat.byte = bq769x0_read_byte(BQ769X0_SYS_STAT);
-
         // first check, if only a new CC reading is available
         if (sys_stat.CC_READY == 1) {
             //printf("Interrupt: CC ready");
@@ -537,7 +538,6 @@ void bms_handle_errors(BmsConfig *conf, BmsStatus *status)
             if (bq769x0_alert_flag() == true) {
                 sec_since_error = 0;
             }
-            error_status = sys_stat.byte;
 
             unsigned int sec_since_interrupt = uptime() - bq769x0_alert_timestamp();
 
@@ -571,7 +571,7 @@ void bms_handle_errors(BmsConfig *conf, BmsStatus *status)
                 }
                 if (sys_stat.byte & 0b00001000) { // UV error
                     bms_read_voltages(status);
-                    if (status->cell_voltage_min > conf->cell_uv_limit) {
+                    if (status->cell_voltage_min > conf->cell_uv_reset) {
                         #if BMS_DEBUG
                         printf("Attempting to clear UV error");
                         #endif
@@ -581,7 +581,7 @@ void bms_handle_errors(BmsConfig *conf, BmsStatus *status)
                 }
                 if (sys_stat.byte & 0b00000100) { // OV error
                     bms_read_voltages(status);
-                    if (status->cell_voltage_max < conf->cell_ov_limit) {
+                    if (status->cell_voltage_max < conf->cell_ov_reset) {
                         #if BMS_DEBUG
                         printf("Attempting to clear OV error");
                         #endif