diff --git a/rk05.cpp b/rk05.cpp
index 44f127b..ab4ee0d 100644
--- a/rk05.cpp
+++ b/rk05.cpp
@@ -25,7 +25,7 @@ static const char * const regnames[] = {
 
 rk05::rk05(bus *const b, std::atomic_bool *const disk_read_acitivity, std::atomic_bool *const disk_write_acitivity) :
 	b(b),
-	disk_read_acitivity(disk_read_acitivity),
+	disk_read_acitivity (disk_read_acitivity ),
 	disk_write_acitivity(disk_write_acitivity)
 {
 }
@@ -281,37 +281,31 @@ void rk05::write_word(const uint16_t addr, const uint16_t v)
 	}
 }
 
-#if IS_POSIX
-json_t *rk05::serialize() const
+JsonDocument rk05::serialize() const
 {
-	json_t *j = json_object();
+	JsonDocument j;
 
-	json_t *j_backends = json_array();
+	JsonArray j_backends;
 	for(auto & dbe: fhs)
-		json_array_append(j_backends, dbe->serialize());
-
-	json_object_set(j, "backends", j_backends);
+		j_backends.add(dbe->serialize());
+	j["backends"] = j_backends;
 
 	for(int regnr=0; regnr<7; regnr++)
-		json_object_set(j, format("register-%d", regnr).c_str(), json_integer(registers[regnr]));
+		j[format("register-%d", regnr)] = registers[regnr];
 
 	return j;
 }
 
-rk05 *rk05::deserialize(const json_t *const j, bus *const b)
+rk05 *rk05::deserialize(const JsonDocument j, bus *const b)
 {
-	std::vector<disk_backend *> backends;
-
 	rk05 *r = new rk05(b, nullptr, nullptr);
 	r->begin();
 
-	json_t *j_backends = json_object_get(j, "backends");
-	for(size_t i=0; i<json_array_size(j_backends); i++)
-		r->access_disk_backends()->push_back(disk_backend::deserialize(json_array_get(j_backends, i)));
+	for(auto j_backend: j["backends"])
+		r->access_disk_backends()->push_back(disk_backend::deserialize(j_backend));
 
 	for(int regnr=0; regnr<7; regnr++)
-		r->registers[regnr] = json_integer_value(json_object_get(j, format("register-%d", regnr).c_str()));
+		r->registers[regnr] = j[format("register-%d", regnr)];
 
 	return r;
 }
-#endif
diff --git a/rk05.h b/rk05.h
index 9d17a93..9d2f6c9 100644
--- a/rk05.h
+++ b/rk05.h
@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <ArduinoJson.h>
 #include <atomic>
 #include <stdint.h>
 #include <stdio.h>
@@ -48,10 +49,8 @@ public:
 
 	void show_state(console *const cnsl) const override;
 
-#if IS_POSIX
-	json_t *serialize() const;
-	static rk05 *deserialize(const json_t *const j, bus *const b);
-#endif
+	JsonDocument serialize() const;
+	static rk05 *deserialize(const JsonDocument j, bus *const b);
 
 	uint8_t  read_byte(const uint16_t addr) override;
 	uint16_t read_word(const uint16_t addr) override;