From a5c594ae5feabdbfcfa50719e34fc6af4ccb140e Mon Sep 17 00:00:00 2001
From: Koen Zandberg <koen@bergzand.net>
Date: Fri, 6 Sep 2019 10:00:32 +0200
Subject: [PATCH] nrfusb: Check chip revision before enabling

Engineering sample A doesn't have a functional USB peripheral (errata
issue 94). This commit adds an assertion check for this revision to
prevent some developer headaches.
---
 cpu/nrf52/periph/usbdev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/cpu/nrf52/periph/usbdev.c b/cpu/nrf52/periph/usbdev.c
index c8a588653a..6b6a1c3916 100644
--- a/cpu/nrf52/periph/usbdev.c
+++ b/cpu/nrf52/periph/usbdev.c
@@ -269,6 +269,9 @@ void usbdev_init_lowlevel(void)
 static void _init(usbdev_t *dev)
 {
     DEBUG("nrfusb: initializing\n");
+    /* Engineering revision version A is affected by errata 94, crash *
+     * instead of pretending to have functional USB                   */
+    assert(NRF_FICR->INFO.VARIANT != 0x41414141);
     nrfusb_t *usbdev = (nrfusb_t*)dev;
     poweron(usbdev);
     usbdev->used = 0;