--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/cs/riviera/rvt/rvt_keepalive.c	Fri May 15 01:28:16 2020 +0000
@@ -0,0 +1,105 @@
+/*
+ * This module is a FreeCalypso addition.  Here we implement the special
+ * operation mode that is only used when a device that was originally
+ * meant to be a phone handset is turned into a pseudo-modem with no UI,
+ * requiring connection to a host computer running rvinterf for control.
+ */
+
+#ifdef PSEUDO_MODEM_KEEPALIVE
+
+#include "nucleus.h"
+
+#include "abb.h"
+
+#include "rv/general.h"
+#include "rv/rv_general.h"
+#include "rvf/rvf_api.h"
+#include "rvt/rvt_gen.h"
+#include "rvt/rvt_def_i.h"
+#include "rvt/rvt_env.h"
+#include "rvt/rvt_env_i.h"
+#include "rvm/rvm_use_id_list.h"
+
+#include "uart/serialswitch.h"
+
+#include <string.h>
+
+volatile UINT8 rvt_keepalive_counter;
+
+void rvt_keepalive_input(T_RVT_BUFFER p_msg, UINT16 msg_length)
+{
+	/* Checking for an invalid PDU. */
+	if ((p_msg == NULL) || (msg_length != 1))
+		return;
+
+	/* Check for the correct opcode */
+	if (*p_msg != 'A')
+		return;
+
+	/* good keepalive response from external host */
+	rvt_keepalive_counter = 0;
+}
+
+void rvt_keepalive_register(void)
+{
+	T_RVT_USER_ID rvt_id;
+
+	rvt_register_id("KEEPALIVE", &rvt_id, rvt_keepalive_input);
+}
+
+static void keepalive_send(UINT8 *buf, UINT32 size)
+{
+	UINT32 sent;
+
+	for (sent = 0; sent < size; )
+		sent += SER_tr_WriteNBytes(SER_LAYER_1, buf + sent,
+					   size - sent);
+}
+
+#ifdef PSEUDO_MODEM_USB
+static char poweroff_msg[] = "System: USB unplugged, powering off";
+#else
+static char poweroff_msg[] = "System: no keepalive response, powering off";
+static UINT8 keepalive_msg[2] = {RVT_KEEPALIVE_HEADER, 'Q'};
+#endif
+
+static void keepalive_poweroff(void)
+{
+	UINT8 poweroff_msg_buf[50], *p;
+
+	p = poweroff_msg_buf;
+	*p++ = RVT_RV_HEADER;
+	*p++ = 0;
+	*p++ = 0;
+	*p++ = 0;
+	*p++ = 0;
+	*p++ = RV_TRACE_LEVEL_ERROR;
+	strcpy((char *)p, poweroff_msg);
+	keepalive_send(poweroff_msg_buf, strlen(poweroff_msg) + 6);
+	/* do it */
+	ABB_Power_Off();
+}
+
+void rvt_keepalive_process(void)
+{
+	SYS_UWORD16 abb_status;
+
+	abb_status = ABB_Read_Status();
+	if (abb_status & CHGPRES) {
+		rvt_keepalive_counter = 0;
+		return;
+	}
+
+#ifdef PSEUDO_MODEM_USB
+	keepalive_poweroff();
+#else
+	if (rvt_keepalive_counter >= 3)
+		keepalive_poweroff();
+	else {
+		rvt_keepalive_counter++;
+		keepalive_send(keepalive_msg, sizeof keepalive_msg);
+	}
+#endif
+}
+
+#endif