diff --git a/cmd/load/main.go b/cmd/load/main.go
index 88d9c60..b2d6faa 100644
--- a/cmd/load/main.go
+++ b/cmd/load/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"log/slog"
 	"os"
@@ -13,7 +14,10 @@ import (
 	"github.com/theater/picomap/lib/picotool"
 )
 
+var target = flag.String("target", "all", "which firmware to load: picomap, picomap_test, or all")
+
 func main() {
+	flag.Parse()
 	wd, err := os.Getwd()
 	if err != nil {
 		slog.Error("fatal", "err", err)
@@ -51,6 +55,13 @@ func boardSerial(id [8]byte) string {
 		id[0], id[1], id[2], id[3], id[4], id[5], id[6], id[7])
 }
 
+type deviceInfo struct {
+	dev    string
+	serial string
+	uf2    string
+	name   string
+}
+
 func run(buildDir string) error {
 	if err := build(buildDir); err != nil {
 		return err
@@ -60,16 +71,39 @@ func run(buildDir string) error {
 	if err != nil {
 		return err
 	}
-	if len(devs) < 2 {
-		return fmt.Errorf("expected 2 devices, found %d", len(devs))
+
+	allTargets := []struct {
+		name string
+		uf2  string
+	}{
+		{"picomap", filepath.Join(buildDir, "picomap.uf2")},
+		{"picomap_test", filepath.Join(buildDir, "picomap_test.uf2")},
 	}
 
-	serials := make([]string, 2)
-	errs := make([]error, 2)
-	uf2Names := []string{"picomap", "picomap_test"}
+	var targets []struct {
+		name string
+		uf2  string
+	}
+	switch *target {
+	case "all":
+		targets = allTargets
+	case "picomap":
+		targets = allTargets[:1]
+	case "picomap_test":
+		targets = allTargets[1:]
+	default:
+		return fmt.Errorf("unknown target %q", *target)
+	}
+
+	if len(devs) < len(targets) {
+		return fmt.Errorf("need %d device(s), found %d", len(targets), len(devs))
+	}
+
+	devices := make([]deviceInfo, len(targets))
+	errs := make([]error, len(targets))
 
 	var wg sync.WaitGroup
-	for i := range 2 {
+	for i := range targets {
 		log := slog.With("dev", devs[i])
 		wg.Go(func() {
 			log.Info("connecting for info")
@@ -84,8 +118,13 @@ func run(buildDir string) error {
 				errs[i] = err
 				return
 			}
-			serials[i] = boardSerial(info.BoardID)
-			log.Info("got info", "serial", serials[i], "firmware", info.FirmwareName)
+			devices[i] = deviceInfo{
+				dev:    devs[i],
+				serial: boardSerial(info.BoardID),
+				uf2:    targets[i].uf2,
+				name:   targets[i].name,
+			}
+			log.Info("got info", "serial", devices[i].serial, "firmware", info.FirmwareName)
 		})
 	}
 	wg.Wait()
@@ -95,11 +134,11 @@ func run(buildDir string) error {
 		}
 	}
 
-	for i := range 2 {
-		log := slog.With("serial", serials[i])
+	for i := range devices {
+		log := slog.With("serial", devices[i].serial)
 		wg.Go(func() {
 			log.Info("sending PICOBOOT")
-			c, err := client.NewSerial(devs[i], 2*time.Second)
+			c, err := client.NewSerial(devices[i].dev, 2*time.Second)
 			if err != nil {
 				errs[i] = err
 				return
@@ -107,38 +146,33 @@ func run(buildDir string) error {
 			err = c.PICOBOOT()
 			c.Close()
 			if err != nil {
-				errs[i] = fmt.Errorf("PICOBOOT %s: %w", serials[i], err)
+				errs[i] = fmt.Errorf("PICOBOOT %s: %w", devices[i].serial, err)
 				return
 			}
 			log.Info("PICOBOOT sent")
 		})
 	}
 	wg.Wait()
-	for _, err := range errs {
+	for i, err := range errs {
 		if err != nil {
-			return err
+			return fmt.Errorf("[%s] %w", devices[i].serial, err)
 		}
 	}
 
-	uf2s := []string{
-		filepath.Join(buildDir, "picomap.uf2"),
-		filepath.Join(buildDir, "picomap_test.uf2"),
-	}
-
-	for i := range 2 {
-		log := slog.With("serial", serials[i])
+	for i := range devices {
+		log := slog.With("serial", devices[i].serial)
 		wg.Go(func() {
-			log.Info("loading", "uf2", uf2Names[i])
-			errs[i] = picotool.Load(uf2s[i], serials[i], 10*time.Second)
+			log.Info("loading", "uf2", devices[i].name)
+			errs[i] = picotool.Load(devices[i].uf2, devices[i].serial, 10*time.Second)
 			if errs[i] == nil {
-				log.Info("loaded", "uf2", uf2Names[i])
+				log.Info("loaded", "uf2", devices[i].name)
 			}
 		})
 	}
 	wg.Wait()
 	for i, err := range errs {
 		if err != nil {
-			return fmt.Errorf("[%s] load: %w", serials[i], err)
+			return fmt.Errorf("[%s] load: %w", devices[i].serial, err)
 		}
 	}
 
diff --git a/firmware/lib/net.cpp b/firmware/lib/net.cpp
index 1281618..7e365eb 100644
--- a/firmware/lib/net.cpp
+++ b/firmware/lib/net.cpp
@@ -172,6 +172,7 @@ const net_state& net_get_state() {
 }
 
 void net_poll() {
+    if (w6300::get_socket_recv_buf(raw_socket) == 0) return;
     static uint8_t rx_buf[1518];
     w6300::ip_address dummy_addr = {};
     w6300::port_num dummy_port{0};