diff --git a/srv/format.c b/srv/format.c
index cad9774..11456a1 100644
--- a/srv/format.c
+++ b/srv/format.c
@@ -21,9 +21,9 @@ uint32_t buffer_write(uint8_t byte, void* arg);
 uint32_t render_format(FormatCallback callback, void* arg,
 		const char* restrict format, va_list va);
 uint32_t render_signed(FormatCallback callback, void* arg,
-		va_list va, uint8_t size, uint8_t base);
+		int32_t number, uint8_t base);
 uint32_t render_unsigned(FormatCallback callback, void* arg,
-		va_list* va, uint8_t size, uint8_t base);
+		uint32_t number, uint8_t base);
 
 
 //--local variables-------------------------------------------------------------
@@ -74,7 +74,6 @@ uint32_t buffer_write(uint8_t byte, void* arg)
 uint32_t render_format(FormatCallback callback, void* arg,
 		const char* restrict format, va_list va)
 {
-	uint8_t size;
 	bool in_format = false;
 
 	for (const char* c = format; *c != '\0'; ++c) {
@@ -84,12 +83,6 @@ uint32_t render_format(FormatCallback callback, void* arg,
 				case '%':
 					callback('%', arg);
 					break;
-				case 'h':
-					size = size / 2;
-					continue;
-				case 'l':
-					size = size * 2;
-					continue;
 				case 'c':
 					callback((uint8_t)va_arg(va, uint32_t), arg);
 					break;
@@ -102,13 +95,13 @@ uint32_t render_format(FormatCallback callback, void* arg,
 					}
 					break;
 				case 'i':
-					//render_signed(callback, arg, va, size, 10);
+					render_signed(callback, arg, va_arg(va, int32_t), 10);
 					break;
 				case 'u':
-					render_unsigned(callback, arg, &va, size, 10);
+					render_unsigned(callback, arg, va_arg(va, uint32_t), 10);
 					break;
 				case 'x':
-					render_unsigned(callback, arg, &va, size, 16);
+					render_unsigned(callback, arg, va_arg(va, uint32_t), 16);
 					break;
 				default:
 					//TODO manage error
@@ -118,7 +111,6 @@ uint32_t render_format(FormatCallback callback, void* arg,
 			switch (*c) {
 				case '%':
 					in_format = true;
-					size = 4;
 					continue;
 				default:
 					callback(*c, arg);
@@ -132,10 +124,20 @@ uint32_t render_format(FormatCallback callback, void* arg,
 	return 0;
 }
 
-uint32_t render_unsigned(FormatCallback callback, void* arg,
-		va_list* va, uint8_t size, uint8_t base)
+uint32_t render_signed(FormatCallback callback, void* arg,
+		int32_t number, uint8_t base)
+{
+	if (number < 0) {
+		callback('-', arg);
+		number = -number;
+	}
+
+	return render_unsigned(callback, arg, (uint32_t)number, base);
+}
+
+uint32_t render_unsigned(FormatCallback callback, void* arg,
+		 uint32_t number, uint8_t base)
 {
-	uint32_t number = va_arg(*va, uint32_t);
 	uint32_t base_power = base;
 
 	while (base_power <= number) {