From dafa6a42823aa518afc6b56c5a08e762b45b1b05 Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@mutantstargoat.com>
Date: Fri, 17 Apr 2020 09:48:53 +0300
Subject: [PATCH] rpi midi recieve test

---
 Makefile   |   11 ++++++++++
 midirecv.c |   29 +++++++++++++++++++++++++++
 uart.c     |   65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 uart.h     |    6 ++++++
 4 files changed, 111 insertions(+)
 create mode 100644 Makefile
 create mode 100644 midirecv.c
 create mode 100644 uart.c
 create mode 100644 uart.h

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ddd10d6
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,11 @@
+obj = midirecv.o uart.o
+bin = midirecv
+
+CFLAGS = -pedantic -Wall -g
+
+$(bin): $(obj)
+	$(CC) -o $@ $(obj) $(LDFLAGS)
+
+.PHONY: clean
+clean:
+	rm -f $(obj) $(bin)
diff --git a/midirecv.c b/midirecv.c
new file mode 100644
index 0000000..673e2d1
--- /dev/null
+++ b/midirecv.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/select.h>
+#include "uart.h"
+
+int main(void)
+{
+	int i, fd, rdsz, count;
+	unsigned char buf[4096];
+
+	if((fd = open("/dev/ttyAMA0", O_RDWR | O_NOCTTY)) == -1) {
+		perror("failed to open serial port /dev/ttyAMA0");
+		return 1;
+	}
+
+	uart_config(31250);
+	write(fd, "U", 1);
+
+	count = 0;
+	while((rdsz = read(fd, buf, sizeof buf)) > 0) {
+		for(i=0; i<rdsz; i++) {
+			printf("%04d: %02x\n", count, (unsigned int)buf[i]);
+		}
+	}
+
+	close(fd);
+	return 0;
+}
diff --git a/uart.c b/uart.c
new file mode 100644
index 0000000..50dd093
--- /dev/null
+++ b/uart.c
@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include "uart.h"
+
+#define CLK				3000000
+
+#define IOBASEADDR		0x3f000000
+#define IOSIZE			16777216
+#define IOREGADDR(x)	((x) | IOBASEADDR)
+
+#define REG_UART_FLAGS	*(volatile uint32_t*)IOREGADDR(0x201018)
+#define	REG_UART_IBRD	*(volatile uint32_t*)IOREGADDR(0x201024)
+#define REG_UART_FBRD	*(volatile uint32_t*)IOREGADDR(0x201028)
+#define REG_UART_LCTL	*(volatile uint32_t*)IOREGADDR(0x20102c)
+#define REG_UART_CTL	*(volatile uint32_t*)IOREGADDR(0x201030)
+
+#define FLAGS_TXEMPTY	0x80
+#define FLAGS_RXFULL	0x40
+#define FLAGS_TXFULL	0x20
+#define FLAGS_RXEMPTY	0x10
+#define FLAGS_BUSY		0x08
+#define FLAGS_CTS		0x01
+
+#define LCTL_8BIT		0x60
+#define LCTL_FIFOEN		0x10
+#define LCTL_PAREN		0x02
+#define LCLT_BRK		0x01
+
+#define CTL_RXEN		0x200
+#define CTL_TXEN		0x100
+#define CTL_EN			0x001
+
+int uart_config(int rate)
+{
+	int fd, div;
+	void *ptr;
+
+	if((fd = open("/dev/mem", O_RDWR)) == -1) {
+		perror("failed to open /dev/mem");
+		return 1;
+	}
+	if((ptr = mmap((void*)IOBASEADDR, IOSIZE, PROT_READ | PROT_WRITE,
+					MAP_SHARED | MAP_FIXED, fd, IOBASEADDR)) == (void*)-1) {
+		perror("failed to map IO space");
+		return 1;
+	}
+
+	REG_UART_CTL = 0;
+	while(REG_UART_FLAGS & FLAGS_BUSY);
+
+	div = (CLK << 6) / (rate << 4);
+	printf("setting divisor (i/f): %d %d\n", div >> 6, div & 0x3f);
+	REG_UART_IBRD = div >> 6;
+	REG_UART_FBRD = div & 0x3f;
+	REG_UART_LCTL = LCTL_8BIT | LCTL_FIFOEN;
+
+	REG_UART_CTL = CTL_RXEN | CTL_TXEN | CTL_EN;
+
+	munmap(ptr, IOSIZE);
+	close(fd);
+	return 0;
+}
diff --git a/uart.h b/uart.h
new file mode 100644
index 0000000..39a765c
--- /dev/null
+++ b/uart.h
@@ -0,0 +1,6 @@
+#ifndef UART_H_
+#define UART_H_
+
+int uart_config(int rate);
+
+#endif	/* UART_H_ */
-- 
1.7.10.4