diff --git a/firmware/ice40-riscv/icE1usb/misc.c b/firmware/ice40-riscv/icE1usb/misc.c
index a25bcc5..4b32fcd 100644
--- a/firmware/ice40-riscv/icE1usb/misc.c
+++ b/firmware/ice40-riscv/icE1usb/misc.c
@@ -71,9 +71,9 @@
 }
 
 uint16_t
-e1_tick_read(void)
+e1_tick_read(int port)
 {
-	return misc_regs->e1_tick[0].tx;
+	return misc_regs->e1_tick[port].tx;
 }
 
 void
diff --git a/firmware/ice40-riscv/icE1usb/misc.h b/firmware/ice40-riscv/icE1usb/misc.h
index 69c0da7..dac5730 100644
--- a/firmware/ice40-riscv/icE1usb/misc.h
+++ b/firmware/ice40-riscv/icE1usb/misc.h
@@ -27,6 +27,6 @@
 void pdm_set(int chan, bool enable, unsigned value, bool normalize);
 
 void e1_led_set(bool enable, uint8_t cfg);
-uint16_t e1_tick_read(void);
+uint16_t e1_tick_read(int port);
 
 void reboot(int fw);
diff --git a/firmware/ice40-riscv/icE1usb/usb_e1.c b/firmware/ice40-riscv/icE1usb/usb_e1.c
index ed4826f..fe94698 100644
--- a/firmware/ice40-riscv/icE1usb/usb_e1.c
+++ b/firmware/ice40-riscv/icE1usb/usb_e1.c
@@ -57,7 +57,7 @@
 	volatile struct usb_ep *ep_regs;
 
 	/* Compute real E1 tick count (with safety against bad values) */
-	ticks = e1_tick_read();
+	ticks = e1_tick_read(0);
 	val = (ticks - ticks_prev) & 0xffff;
 	ticks_prev = ticks;
 	if ((val < 7168) | (val > 9216))