From 1f90cffc896b84cdc571aef88dfe09655471adfe Mon Sep 17 00:00:00 2001
From: Hierophect <hierophect@gmail.com>
Date: Mon, 30 Sep 2019 13:33:20 -0400
Subject: protect against edge case

---
 ports/stm32f4/common-hal/busio/SPI.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/ports/stm32f4/common-hal/busio/SPI.c b/ports/stm32f4/common-hal/busio/SPI.c
index a13b3dfdb..d64ec542a 100644
--- a/ports/stm32f4/common-hal/busio/SPI.c
+++ b/ports/stm32f4/common-hal/busio/SPI.c
@@ -97,10 +97,12 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
                 if (mcu_spi_mosi_list[j].pin == mosi) {
                     //miso
                     for(uint k=0; k<miso_len;k++) {
-                        if ((mcu_spi_miso_list[k].pin == miso)
+                        if ((mcu_spi_miso_list[k].pin == miso) //everything needs the same index
                             && (mcu_spi_sck_list[i].spi_index == mcu_spi_mosi_list[j].spi_index)
                             && (mcu_spi_sck_list[i].spi_index == mcu_spi_miso_list[k].spi_index)) {
-                            //everything needs the same index
+                            //keep looking if the SPI is taken, edge case
+                            if(reserved_spi[mcu_spi_sck_list[i].spi_index-1]) continue;
+                            //store pins if not
                             self->sck = &mcu_spi_sck_list[j];
                             self->mosi = &mcu_spi_mosi_list[j];
                             self->miso = &mcu_spi_miso_list[k];
-- 
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