From 1d68f2a3280cdc76912ec7e89238640e950e542c Mon Sep 17 00:00:00 2001
From: hathach <thach@tinyusb.org>
Date: Fri, 8 Sep 2023 18:39:09 +0700
Subject: [PATCH] metro m4 working with max3421e

---
 hw/bsp/samd51/family.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/hw/bsp/samd51/family.c b/hw/bsp/samd51/family.c
index 45a9aa5e0..51cfd19ba 100644
--- a/hw/bsp/samd51/family.c
+++ b/hw/bsp/samd51/family.c
@@ -294,7 +294,7 @@ bool tuh_max3421_spi_xfer_api(uint8_t rhport, uint8_t const *tx_buf, size_t tx_l
   size_t count = 0;
   while (count < tx_len || count < rx_len) {
     // Wait for the transmit buffer to be empty
-//    while (!SERCOM2->SPI.INTFLAG.bit.DRE);
+    while (!SERCOM2->SPI.INTFLAG.bit.DRE);
 
     // Write data to be transmitted
     uint8_t data = 0x00;
@@ -302,19 +302,24 @@ bool tuh_max3421_spi_xfer_api(uint8_t rhport, uint8_t const *tx_buf, size_t tx_l
        data = tx_buf[count];
     }
 
-    SERCOM2->SPI.DATA.bit.DATA = data;
+    SERCOM2->SPI.DATA.reg = (uint32_t) data;
 
     // Wait for the receive buffer to be filled
     while (!SERCOM2->SPI.INTFLAG.bit.RXC);
 
     // Read received data
-    if (rx_buf) {
-      rx_buf[count] = SERCOM2->SPI.DATA.bit.DATA;
+    data = (uint8_t) SERCOM2->SPI.DATA.reg;
+    if (count < rx_len) {
+      rx_buf[count] = data;
     }
 
     count++;
   }
 
+  // wait for bus idle and clear flags
+  while (!(SERCOM2->SPI.INTFLAG.reg & (SERCOM_SPI_INTFLAG_TXC | SERCOM_SPI_INTFLAG_DRE)));
+  SERCOM2->SPI.INTFLAG.reg = SERCOM_SPI_INTFLAG_TXC | SERCOM_SPI_INTFLAG_DRE;
+
   return true;
 }
 #endif