prevent bat from going negative

src/main.c

@@ -12,6 +12,7 @@
 #include <net/if.h>
 #include <fcntl.h>
 #include <termios.h>
+#include <errno.h>
 
 const int digit_bitmaps[10][5][3] = {
         {{1,1,1},{1,0,1},{1,0,1},{1,0,1},{1,1,1}}, // 0
@@ -172,6 +173,35 @@ void read_uart(Tel *t, int fd, SerialParser *uart_str) {
         }
 }
 
+void write_uart(Tel *t, int fd) {
+        // speed,rpm,power,eff,bat,tens,amp,warn
+        char msg[256];
+        int len = snprintf(msg, sizeof(msg), "%d,%d,%d,%.1f,%d,%.1f,%.1f,%d\n",
+        t->speed.data,
+        t->rpm.data,
+        t->power.data,
+        t->eff.data,
+        t->bat.data,
+        t->tens.data,
+        t->amp.data,
+        t->message.error_level );
+
+        if (len < 0 || len >= (int)sizeof(msg)) {
+                return;
+        }
+
+        int total = 0;
+        while (total < len) {
+                int n = write(fd, msg + total, len - total);
+                if (n < 0) {
+                        if (errno == EINTR) continue;
+                        if (errno == EAGAIN) continue;
+                        return;
+                }
+                total += n;
+        }
+}
+
 void calc_data(Tel *t, Bat_state *b, long now) {
         t->power.data = (int)(t->tens.data * t->amp.data);
         t->speed.data = (int)(t->rpm.data * 0.017f);
@@ -188,6 +218,7 @@ void calc_data(Tel *t, Bat_state *b, long now) {
 
         b->previous_ms = now;
         b->wh_used += (float)t->power.data * (float)dt / 3600000.0f;
+        if (b->wh_used > b->wh_total) b->wh_used = b->wh_total;
 }
 
 long now_ms(void) {
@@ -655,6 +686,9 @@ int main(int argc, char **argv) {
                         win_float(&tel.amp, use_color);
                         win_int(&tel.bat, use_color);
                         win_warn(&tel, use_color, now);
+
+                        if (use_uart) write_uart(&tel, uart_fd);
+
                         t100 = now;
                 }
                 napms(10);