altos: Make micropeak 'serial' interface work

I prototyped the mpserial interface on a breadboard and tuned the
circuit to register the LED correctly. Then adjusted the serial code
to send bits at the right speed and format.

The logging contents are now in hexdecimal with a CCITT CRC-16
computed to verify correct reception.

Signed-off-by: Keith Packard <keithp@keithp.com>

5 files changed, 99 insertions, 8 deletions

diff --git a/src/micropeak/Makefile b/src/micropeak/Makefile
index 82944cb1..ff0a4499 100644
--- a/src/micropeak/Makefile
+++ b/src/micropeak/Makefile
@@ -50,7 +50,7 @@ IDPRODUCT=0
 PRODUCT=MicroPeak-v0.1
 PRODUCT_DEF=-DMICROPEAK
 CFLAGS = $(PRODUCT_DEF) -I. -I../attiny -I../core -I.. -I../drivers
-CFLAGS += -g -mmcu=$(MCU) -Wall -Wstrict-prototypes -O3 -mcall-prologues -DATTINY
+CFLAGS += -g -mmcu=$(MCU) -Wall -Wstrict-prototypes -O2 -mcall-prologues -DATTINY
 
 NICKLE=nickle
 
diff --git a/src/micropeak/ao_async.c b/src/micropeak/ao_async.c
index 04bba9e8..3556f54c 100644
--- a/src/micropeak/ao_async.c
+++ b/src/micropeak/ao_async.c
@@ -21,20 +21,51 @@
 #define AO_ASYNC_BAUD	38400l
 #define AO_ASYNC_DELAY	(uint8_t) (1000000l / AO_ASYNC_BAUD)
 
+#define LED_PORT	PORTB
+
+void
+ao_async_start(void)
+{
+	LED_PORT |= (1 << AO_LED_SERIAL);
+}
+
+void
+ao_async_stop(void)
+{
+	LED_PORT &= ~(1 << AO_LED_SERIAL);
+}
+
 void
 ao_async_byte(uint8_t byte)
 {
 	uint8_t		b;
 	uint16_t	w;
 
-	/* start bit */
-
-	/* start     data         stop */
-	w = 0x001 | (byte << 1) | 0x000;
+	/*    start           data           stop */
+	w = (0x000 << 0) | (byte << 1) | (0x001 << 9);
 
+	ao_arch_block_interrupts();
 	for (b = 0; b < 10; b++) {
-		ao_led_set((w & 1) << AO_LED_SERIAL);
+		uint8_t	v = LED_PORT & ~(1 << AO_LED_SERIAL);
+		v |= (w & 1) << AO_LED_SERIAL;
+		LED_PORT = v;
 		w >>= 1;
-		ao_delay_us(26);
+
+		/* Carefully timed to hit around 9600 baud */
+		asm volatile ("nop");
+		asm volatile ("nop");
+
+		asm volatile ("nop");
+		asm volatile ("nop");
+		asm volatile ("nop");
+		asm volatile ("nop");
+		asm volatile ("nop");
+
+		asm volatile ("nop");
+		asm volatile ("nop");
+		asm volatile ("nop");
+		asm volatile ("nop");
+		asm volatile ("nop");
 	}
+	ao_arch_release_interrupts();
 }
diff --git a/src/micropeak/ao_async.h b/src/micropeak/ao_async.h
index a06d2e1a..1b239712 100644
--- a/src/micropeak/ao_async.h
+++ b/src/micropeak/ao_async.h
@@ -19,6 +19,12 @@
 #define _AO_ASYNC_H_
 
 void
+ao_async_start(void);
+
+void
+ao_async_stop(void);
+
+void
 ao_async_byte(uint8_t byte);
 
 #endif /* _AO_ASYNC_H_ */
diff --git a/src/micropeak/ao_log_micro.c b/src/micropeak/ao_log_micro.c
index 40a7a35d..d665efb5 100644
--- a/src/micropeak/ao_log_micro.c
+++ b/src/micropeak/ao_log_micro.c
@@ -49,6 +49,46 @@ ao_log_micro_data(void)
 	}
 }
 
+#define POLY 0x8408
+
+static uint16_t
+ao_log_micro_crc(uint16_t crc, uint8_t byte)
+{
+	uint8_t	i;
+
+	for (i = 0; i < 8; i++) {
+		if ((crc & 0x0001) ^ (byte & 0x0001))
+			crc = (crc >> 1) ^ POLY;
+		else
+			crc = crc >> 1;
+		byte >>= 1;
+	}
+	return crc;
+}
+
+static void
+ao_log_hex_nibble(uint8_t b)
+{
+	if (b < 10)
+		ao_async_byte('0' + b);
+	else
+		ao_async_byte('a' - 10 + b);
+}
+
+static void
+ao_log_hex(uint8_t b)
+{
+	ao_log_hex_nibble(b>>4);
+	ao_log_hex_nibble(b&0xf);
+}
+
+static void
+ao_log_newline(void)
+{
+	ao_async_byte('\r');
+	ao_async_byte('\n');
+}
+
 void
 ao_log_micro_dump(void)
 {
@@ -56,13 +96,26 @@ ao_log_micro_dump(void)
 	uint16_t	nbytes;
 	uint8_t		byte;
 	uint16_t	b;
+	uint16_t	crc = 0xffff;
 
 	ao_eeprom_read(N_SAMPLES_OFFSET, &n_samples, sizeof (n_samples));
+	if (n_samples == 0xffff)
+		n_samples = 0;
 	nbytes = STARTING_LOG_OFFSET + sizeof (uint16_t) * n_samples;
+	ao_async_start();
 	ao_async_byte('M');
 	ao_async_byte('P');
 	for (b = 0; b < nbytes; b++) {
+		if ((b & 0xf) == 0)
+			ao_log_newline();
 		ao_eeprom_read(b, &byte, 1);
-		ao_async_byte(byte);
+		ao_log_hex(byte);
+		crc = ao_log_micro_crc(crc, byte);
 	}
+	ao_log_newline();
+	crc = ~crc;
+	ao_log_hex(crc >> 8);
+	ao_log_hex(crc);
+	ao_log_newline();
+	ao_async_stop();
 }
diff --git a/src/micropeak/ao_micropeak.c b/src/micropeak/ao_micropeak.c
index 3bbc7eea..f579a09a 100644
--- a/src/micropeak/ao_micropeak.c
+++ b/src/micropeak/ao_micropeak.c
@@ -19,6 +19,7 @@
 #include <ao_micropeak.h>
 #include <ao_ms5607.h>
 #include <ao_log_micro.h>
+#include <ao_async.h>
 
 static struct ao_ms5607_sample	sample;
 static struct ao_ms5607_value	value;