--- a/.hgignore	Mon Sep 11 04:55:27 2023 +0000
+++ b/.hgignore	Mon Sep 11 17:41:24 2023 +0000
@@ -2,6 +2,8 @@
 
 \.[oa]$
 
+^cp2102/cp2102-read-partno$
+
 ^duart28/fc-duart28-conf$
 
 ^fteeprom/ftee-gen2232c$

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cp2102/Makefile	Mon Sep 11 17:41:24 2023 +0000
@@ -0,0 +1,20 @@
+CC=	gcc
+CFLAGS=	-O2
+PROGS=	cp2102-read-partno
+LIBS=	../libuwrap/libuwrap.a
+
+INSTALL_PREFIX=	/opt/freecalypso
+
+INSTBIN=${INSTALL_PREFIX}/bin
+
+all:	${PROGS}
+
+cp2102-read-partno:	read_partno.o ${LIBS}
+	${CC} ${CFLAGS} -o $@ read_partno.o ${LIBS} -lusb
+
+install:
+	mkdir -p ${INSTBIN}
+	install -c ${PROGS} ${INSTBIN}
+
+clean:
+	rm -f ${PROGS} *.o *errs *.out

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cp2102/cp210x_defs.h	Mon Sep 11 17:41:24 2023 +0000
@@ -0,0 +1,35 @@
+/*
+ * Definitions for talking to CP2102 and perhaps other CP210x chips,
+ * taken from Python-based cp210x-program-1.0 tool from 2014,
+ * translated from Python to C.
+ */
+
+#define	CP210x_CONFIG		0xFF
+
+#define	REG_VENDOR_ID		0x3701
+#define	REG_PRODUCT_ID		0x3702
+#define	REG_PRODUCT_STRING	0x3703
+#define	REG_SERIAL_NUMBER	0x3704
+#define	REG_CFG_ATTRIBUTES	0x3705
+#define	REG_MAX_POWER		0x3706
+#define	REG_VERSION		0x3707
+#define	REG_UNKNOWN		0x3708
+#define	REG_EEPROM		0x3709
+#define	REG_LOCK_VALUE		0x370A
+#define	REG_PART_NUMBER		0x370B
+
+#define	SIZE_EEPROM		0x0400
+#define	SIZE_PRODUCT_STRING	255
+#define	SIZE_SERIAL_NUMBER	128
+#define	SIZE_BAUDRATES		32
+#define	SIZE_BAUDRATE_CFG	10
+#define	SIZE_BAUDRATE_TABLE	(SIZE_BAUDRATES * SIZE_BAUDRATE_CFG)
+#define	SIZE_VENDOR_STRING	50
+
+/* a little bit adapted from libftdi */
+
+#define DEVICE_OUT_REQTYPE (USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_OUT)
+#define DEVICE_IN_REQTYPE (USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN)
+
+#define	USB_READ_TIMEOUT	5000
+#define	USB_WRITE_TIMEOUT	5000

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cp2102/read_partno.c	Mon Sep 11 17:41:24 2023 +0000
@@ -0,0 +1,51 @@
+/*
+ * This program locates a presumed-CP2102 device via libusb and reads its
+ * vendor-specific part number register, seeking to distinguish between
+ * the original CP2102 and the later CP2102N.
+ */
+
+#include <sys/types.h>
+#include <string.h>
+#include <strings.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <usb.h>
+#include "../libuwrap/find_dev.h"
+#include "cp210x_defs.h"
+
+main(argc, argv)
+	char **argv;
+{
+	struct usb_device *dev;
+	usb_dev_handle *usbh;
+	u_char partno;
+	int rc;
+
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s device-selector\n", argv[0]);
+		exit(1);
+	}
+	dev = find_usbdev_by_desc_string(argv[1]);
+	if (!dev) {
+		fprintf(stderr, "error: specified USB device not found\n");
+		exit(1);
+	}
+	usbh = usb_open(dev);
+	if (!usbh) {
+		fprintf(stderr, "error: usb_open() failed\n");
+		exit(1);
+	}
+	rc = usb_control_msg(usbh, DEVICE_IN_REQTYPE, CP210x_CONFIG, 0,
+			     REG_PART_NUMBER, (char *) &partno, 1,
+			     USB_READ_TIMEOUT);
+	if (rc != 1) {
+		fprintf(stderr,
+		"REG_PART_NUMBER read error: usb_control_msg() returned %d\n",
+			rc);
+		exit(1);
+	}
+	usb_close(usbh);
+	printf("0x%02X\n", partno);
+	exit(0);
+}