# HG changeset patch
# User Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
# Date 1721044974 14400
#      Mon Jul 15 08:02:54 2024 -0400
# Node ID 2270713edaecd831e0a8f5b3f73352a345ce31af
# Parent  43d2a8cd5054c423dd77e350762ad8039ea45410
arch: add function to concurrently send and receive SPI data (ATmega48P)

Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>

diff --git a/arch/atmega48p_spi.h b/arch/atmega48p_spi.h
--- a/arch/atmega48p_spi.h
+++ b/arch/atmega48p_spi.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023 Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
+ * Copyright (c) 2023-2024 Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -140,6 +140,20 @@
 		;
 }
 
+/* send & receive a single byte, CS is left up to the caller */
+static inline uint8_t spi_txrx_byte(uint8_t dummy)
+{
+	mmregs->spdr = dummy;
+
+	/* wait for rx to complete */
+	while (!(mmregs->spsr & REG_SPSR_SPIF))
+		;
+
+	return mmregs->spdr;
+}
+
+#define spi_rx_byte() spi_txrx_byte(0)
+
 #endif
 
 #endif