cmd: K set clock, D test data test

.gitignore

@@ -18,3 +18,6 @@ gerber/*.pdf
 *.EI
 src/calib
 src/mul
+*.bin
+*.eeprom
+*.elf

src/#Makefile#

@@ -0,0 +1,163 @@
+
+PROJ=bate
+
+PATH:=/usr/local/bin:$(PATH)
+
+default: all
+all: $(PROJ).hex
+
+SN_bate = 1
+MCU_bate = attiny424
+C_FILES_bate = uart.c rtc.c spi.c adc.c calib.c mul.c cmd.c
+S_FILES_bate = uart_tx.S
+
+MCU = $(MCU_$(PROJ))
+# When flash gets tight, use `OPT=-Os`, or use more assembler :-)
+OPT = -O2
+
+CC=avr-gcc -Wall -Wno-parentheses -MMD -std=c99 $(OPT) \
+  -mmcu=$(MCU) \
+  -funsigned-char \
+  -funsigned-bitfields \
+  -fpack-struct \
+  -fshort-enums \
+  -mtiny-stack \
+  -mint8 \
+  -fverbose-asm
+
+SN = $(SN_$(PROJ))
+CFLAGS = $($*_CFLAGS) $(DEBUG) -I. -DSN="$(SN)"
+
+C_FILES = $(C_FILES_$(PROJ))
+S_FILES = $(S_FILES_$(PROJ))
+OBJS = $(patsubst %.c, %.o, $(C_FILES)) $(patsubst %.S, %.o, $(S_FILES))
+
+%.s: %.c %.o
+	$(CC) $(CFLAGS) -S $<
+
+%.o: %.c
+	$(CC) -g $(CFLAGS) -c $<
+
+%.o: %.S
+	$(CC) -g $(CFLAGS) -c $<
+
+-include *.d
+
+LDFLAGS = -Teeprom.ld
+
+%.elf: %.o $(OBJS)
+	$(CC) $(CFLAGS) -Wl,-Map=$*.map,--cref $^ --output $@ $(LDFLAGS)
+
+OBJCOPY = avr-objcopy
+
+%.hex: %.elf
+	$(OBJCOPY) -O ihex -R .eeprom -R .eemap $< $@
+
+%.eeprom: %.elf
+	$(OBJCOPY) -O ihex -j .eemap --change-section-lma .eemap=0 $< $@
+
+
+pMCU-attiny424 = t424
+
+#
+#avrdude> dump fuses
+#>>> dump fuses 0x0 0x9
+#
+#Reading | ################################################## | 100% 0.13 s 
+#
+#0000  00 00 7e ff ff f6 ff 00  00                       |..~......       |
+#
+#avrdude> 
+
+# WDT
+fuse0_bate= 0x00
+# BOD
+fuse1_bate= 0x00
+# OSC, 20 MHz
+fuse2_bate= 0x7e
+# ???
+fuse4_bate= 0xff
+# SYS0 (default 0xf6)  RESET, EEPROM erase
+fuse5_bate= 0xf7
+# SYS1 startup time (64ms)
+fuse6_bate= 0xff 
+# APPEND
+fuse7_bate= 0x00 
+# BOOTEND
+fuse8_bate= 0x00
+fuses_bate =$(patsubst %, 0x%, 00 00 7e ff ff f7 ff 00  00)
+
+AVRDUDEPROG = avrdude
+AVRDUDE = $(AVRDUDEPROG)
+AVRDUDE_PROGRAMMER = serialupdi
+AVRDUDE_PORT = /dev/ttyUSB1
+
+AD = $(AVRDUDE) -p $(pMCU-$(MCU)) -P $(AVRDUDE_PORT) -c $(AVRDUDE_PROGRAMMER)
+
+sig_bate = 0x1e 0x92 0x2c
+
+id: $(PROJ).id
+%.id:
+	$(AD) -qq -U signature:v:"$(sig_$*)":m
+
+ad: $(PROJ).ad
+%.ad:
+	$(AD) -v -t
+
+%.burn: %.hex
+	$(AD) -U flash:v:$< || $(AD) -U flash:w:$<
+
+%.verify: %.hex %.eeprom
+	-$(AD) -qq -U fuses:v:"$(fuses_$*)":m
+	-$(AD) -qq -U userrow:v:"$(BATE_CONFIG)":m
+	-$(AD) -qq -U eeprom:v:$(word 2, $^)
+	-$(AD) -qq -U flash:v:$<
+
+fuse: $(PROJ).fuse$F
+
+%.fuse$F:
+	echo "$*: fuse$F = $(fuse$F_$*)"
+	[ -n "$(fuse$F_$*)" ] && $(AD) -B 5 -U fuse$F:w:$(fuse$F_$*):m
+
+# see bate.c: Configuration in USERROW
+BC_MAGIC = 0xba
+BC_VERS  = 6
+BC_TRIG  = 0x28
+BC_SEND  = 0x59
+BC_PWR   = 0x7c
+BC_TEST  = 0
+BC_SPI   = 0xff
+BC_MDEL  = 2
+BC_PER   = 9 0
+BC_CPER  = 43 1
+
+BC_CLK   = 1
+BC_MCLK  = 0
+BC_BAUD  = 0 0
+BC_UART  = 0xd0
+BC_PIT   = 0xff
+BC_IMM   = 5
+
+BATE_CONFIG = $(BC_MAGIC) $(BC_VERS) \
+              $(BC_TRIG) $(BC_SEND) $(BC_PWR) $(BC_TEST) \
+              $(BC_SPI) $(BC_MDEL) $(BC_PER) $(BC_CPER) \
+              $(BC_CLK) $(BC_MCLK) $(BC_BAUD) $(BC_UART) \
+              $(BC_PIT) $(BC_IMM)
+
+bate.config:
+	$(AD) -U userrow:v:"$(BATE_CONFIG)":m \
+     ||	$(AD) -U userrow:w:"$(BATE_CONFIG)":m
+
+clean:
+	rm -f *.hex *.o *.s *.map *.elf *.d
+
+.PHONY: eeprom.eeprom
+eeprom.eeprom:
+	$(AD) -U eeprom:r:$@
+%.eeprom.burn: %.eeprom
+	$(AD) -U eeprom:v:$< || $(AD) -U eeprom:w:$< 
+
+calib: calib.c mul.c
+	gcc -DCALIB_DEBUG -o $@ $<
+mul: mul.c
+	gcc -DMUL_TEST -o $@ $<

src/.#Makefile

@@ -0,0 +1 @@
+stephan@blaulicht.31918:1708279459

src/Makefile

@@ -121,26 +121,28 @@ fuse: $(PROJ).fuse$F
 
 # see bate.c: Configuration in USERROW
 BC_MAGIC = 0xba
-BC_VERS  = 5
+BC_VERS  = 6
-BC_TRIG  = 0x08
+BC_TRIG  = 0x28
-BC_SEND  = 0x2b
+BC_SEND  = 0x59
-BC_PWR   = 0x04
+BC_PWR   = 0x2d
-BC_TEST  = 5
+BC_TEST  = 0
 BC_SPI   = 0xff
 BC_MDEL  = 2
-BC_PER   = 59 0
+BC_PER   = 9 0
-BC_CPER  = 15 14
+BC_CPER  = 43 1
 
 BC_CLK   = 1
 BC_MCLK  = 0
 BC_BAUD  = 0 0
 BC_UART  = 0xd0
 BC_PIT   = 0xff
+BC_IMM   = 5
 
 BATE_CONFIG = $(BC_MAGIC) $(BC_VERS) \
               $(BC_TRIG) $(BC_SEND) $(BC_PWR) $(BC_TEST) \
               $(BC_SPI) $(BC_MDEL) $(BC_PER) $(BC_CPER) \
-              $(BC_CLK) $(BC_MCLK) $(BC_BAUD) $(BC_UART) $(BC_PIT)
+              $(BC_CLK) $(BC_MCLK) $(BC_BAUD) $(BC_UART) \
+              $(BC_PIT) $(BC_IMM)
 
 bate.config:
 	$(AD) -U userrow:v:"$(BATE_CONFIG)":m \

src/bate.c

@@ -356,17 +356,21 @@ void read_bate()
 //  Configuration in USERROW
 
 struct config config = {
-	.power      = STOP_MCLK,
+	.power      = STOP_MCLK | POWER_STDBY | POWER_LED | POWER_RF,
-	.send       = SEND_CONFIG | SEND_CLOCK | SEND_BATED | SEND_ADC,
+	.send       = SEND_CONFIG | SEND_CLOCK | SEND_BATED | SEND_ADC_HEX,
 	.cpu_clk    = CLKCTRL_PDIV_2X_gc | 1,
 	.pit_period = RTC_CLKSEL_INT1K_gc,
 	.spi_div    = SPI_PRESC_DIV64_gc,
-	.triggers   = TRIGGER_CLOCK,
+	.triggers   = TRIGGER_CLOCK | TRIGGER_IMMED,
 	.mclk_delay = 2,
 	.period     = 59,
 	.cperiod    = 3599,
+	.uart_mode  = UART_Tx | UART_Rx | UART_SFD,
 };
 
+uint8_t immediate;
+uint8_t test_calib;
+
 static const struct config *userrow = (struct config *) & USERROW;
 
 #ifdef DEBUG
@@ -412,14 +416,10 @@ int main()
 
 	uint8_t reset_source = RSTCTRL.RSTFR;
 	RSTCTRL.RSTFR = reset_source;
-	send_str("\nV Turbo Weather V0.05\nB ");
+	send_str("\nV Turbo Weather V0.7\nB ");
 	send_hex_byte(reset_source);
 	send_eol();
 
-	uint8_t test_calib = config.calib_test;
-	if (test_calib > N_TESTDATA)
-		test_calib = N_TESTDATA;
-
 	uint8_t n_adc = 0;
 	while (n_adc < N_ADC && adc_conf[n_adc].mode && adc_conf[n_adc].mode != 0xff)
 		n_adc++;
@@ -430,10 +430,27 @@ int main()
 	static uint16_t config_clock = 0;
 	uint8_t send_config = 1;
 	uint8_t uart_rx_delay = 0;
+	immediate = config.immediate;
+	test_calib = config.calib_test;
 
 	while (1) {
 		DEBUG_COUNTER(mainloops);
 		sleep_cpu();
+		set_sleep_mode(SLEEP_MODE_IDLE);
+
+		if (clock_tick) {
+			clock_tick = 0;
+			if (!trigger_clock--) {
+				trigger |= TRIGGER_CLOCK;
+				trigger_clock = config.period;
+			}
+			if (config.send & SEND_CONFIG && !config_clock--) {
+				send_config = 1;
+				config_clock = config.cperiod;
+			}
+			if (uart_rx_delay)
+				uart_rx_delay--;
+		}
 
 		if (config.send & SEND_ADC  &&  adc_current <= N_ADC) {
 			if (adc_busy())
@@ -469,26 +486,15 @@ int main()
 			// Keep the power up for this second,
 			// to give the SFD a chance.
 			if (config.power & POWER_RX)
-				uart_rx_delay = 1;
+				uart_rx_delay = 2;
 		}
-		else if (clock_tick)
+
-			uart_rx_delay = 0;
 		if (uart_break_p())
 			trigger |= TRIGGER_BREAK;
 
-		if (clock_tick) {
+		if (immediate || test_calib)
-			clock_tick = 0;
+			trigger |= TRIGGER_IMMED;
-			if (test_calib)
+
-				trigger |= TRIGGER_CLOCK;
-			else if (!trigger_clock--) {
-				trigger |= TRIGGER_CLOCK;
-				trigger_clock = config.period;
-			}
-			if (config.send & SEND_CONFIG && !config_clock--) {
-				send_config = 1;
-				config_clock = config.cperiod;
-			}
-		}
 		if (!(trigger & config.triggers)) {
 			if (config.power & (POWER_DOWN|POWER_STDBY)) {
 				mclk(0);
@@ -499,14 +505,12 @@ int main()
 				}
 				else
 					set_sleep_mode(SLEEP_MODE_STANDBY);
-				sleep_enable();
-				sleep_cpu();
-				set_sleep_mode(SLEEP_MODE_IDLE);
 			}
 			continue;
 		}
 
-		rfen(1);
+		if (config.power & POWER_RF)
+			rfen(1);
 		if (config.power & POWER_LED)
 			led(1);
 
@@ -523,6 +527,9 @@ int main()
 			continue;
 		}
 
+		if (immediate)
+			immediate--;
+
 		read_bate();
 		if (config.power & STOP_MCLK)
 			mclk(0);
@@ -530,6 +537,15 @@ int main()
 		if (config.send & SEND_ADC)
 			start_adc();
 
+		if (send_config) {
+			send_config = 0;
+			send_hex('S', (uint8_t *)&SIGROW, sizeof(SIGROW_t), 0);
+			send_hex('F', (uint8_t *)&FUSE, sizeof(FUSE_t), 1);
+			send_hex('U', (uint8_t *)&USERROW, sizeof(USERROW_t), 1);
+			send_hex('C', (uint8_t *)&config, sizeof(struct config), 1);
+			send_hex('E', (uint8_t *)adc_conf, sizeof(adc_conf), 3);
+		}
+
 		if (config.send & SEND_CLOCK) {
 			send_str("T 0x");
 			cli();
@@ -542,12 +558,15 @@ int main()
 		uint8_t send_test = 0;
 		const union bate *b = &bate;
 		if (test_calib) {
+			if (test_calib > N_TESTDATA)
+				test_calib = N_TESTDATA;
 			b = testdata + -- test_calib;
 			send_test = 1;
+			send_config = 1;
 		}
 		if (config.send & SEND_BATEW || send_config)
 			send_hex('W', b->b, 8, 3);
-		if (config.send & SEND_BATED || send_test)
+		if (config.send & SEND_BATED || send_config)
 			send_hex('D', b->b+8, 4, 3);
 		if (config.send & SEND_CALIB || send_test) {
 			bate_calib(b, &pressure);
@@ -558,15 +577,6 @@ int main()
 			send_str(" °C\n");
 		}
 
-		if (send_config) {
-			send_config = 0;
-			send_hex('S', (uint8_t *)&SIGROW, sizeof(SIGROW_t), 0);
-			send_hex('F', (uint8_t *)&FUSE, sizeof(FUSE_t), 1);
-			send_hex('U', (uint8_t *)&USERROW, sizeof(USERROW_t), 1);
-			send_hex('C', (uint8_t *)&config, sizeof(struct config), 1);
-			send_hex('E', (uint8_t *)adc_conf, sizeof(adc_conf), 3);
-		}
-
 		if (config.send & SEND_DEBUG) {
 			DEBUG_PRINT(0x77, trigger);
 		}

src/bate.h

@@ -24,14 +24,14 @@ struct config {
 	uint16_t  baud_div;
 	uint8_t   uart_mode;
 	uint8_t   pit_period;
+	uint8_t	  immediate;
+	uint8_t   pad;
 };
 
 enum magic_flags {
 	USE_USERROW       = 0xBA,
-	USE_VERSION       = 0x05,
+	USE_VERSION       = 0x07,
 };
-
-
 enum power_flags {
 	POWER_DOWN        = 0x01,
 	POWER_DOWN_CLI    = 0x02,
@@ -39,6 +39,7 @@ enum power_flags {
 	POWER_LED         = 0x08,
 	POWER_STDBY       = 0x10,
 	POWER_RX          = 0x20,
+	POWER_RF          = 0x40,
 };
 enum send_flags {
 	SEND_CONFIG       = 0x01,
@@ -57,6 +58,7 @@ enum trigger_flags {
 	TRIGGER_UART  = 0x04,
 	TRIGGER_CLOCK = 0x08,
 	TRIGGER_BREAK = 0x10,
+	TRIGGER_IMMED = 0x20,
 };
 enum UART_flags { // USART0.CTRLB
 	UART_Tx       = /* 0x40, */ USART_TXEN_bm,
@@ -69,6 +71,8 @@ enum UART_flags { // USART0.CTRLB
 };
 
 extern struct config config;
+extern uint8_t immediate;
+extern uint8_t test_calib;
 
 #ifndef NODEBUG
 #   define  DEBUG
@@ -88,9 +92,16 @@ struct debug {
 		uint8_t adc_irqs;
 		uint8_t rx_char;
 	};
-	uint8_t bate_timeout;
+	union {
-	uint8_t spi_timeout;
+		uint8_t bate_timeout;
-	uint16_t mainloops;
+		uint8_t rxhex;
+	};
+	union {
+		uint8_t spi_timeout;
+		uint8_t rxpar;
+	};
+	uint8_t mainloops;
+	uint8_t pit_irqs;
 };
 
 extern struct debug debug_data;

src/cmd.c

@@ -3,6 +3,7 @@
 //
 
 #include "bate.h"
+#include "rtc.h"
 #include <string.h>
 
 #ifdef NOCMD
@@ -10,6 +11,10 @@
 void parse_command(uint8_t *s, uint8_t n) {}
 #else
 
+uint8_t rx_params[8];
+
+#if 0
+
 __attribute__ ((noinline, noclone))
 uint8_t parse_hex_nibble(uint8_t c)
 {
@@ -20,15 +25,11 @@ uint8_t parse_hex_nibble(uint8_t c)
 	return 0xf0;
 }
 
-uint8_t rx_params[8];
+static inline
-
+uint8_t parse_rx_params(uint8_t *s, uint8_t n)
-void parse_command(uint8_t *s, uint8_t n)
 {
-	if (!n)
+	uint8_t p;
-		return;
+	p = 0;
-	uint8_t cmd = *s++;
-	uint8_t p = 0;
-	n--;
 	while (n) {
 		while (n) {
 			if (*s != ' ')
@@ -43,39 +44,170 @@ void parse_command(uint8_t *s, uint8_t n)
 			break;
 		n--;
 		s++;
-		uint8_t h = 0;
 		if (n) {
+			uint8_t h = 0;
 			h = parse_hex_nibble(*s);
 			if (h != 0xf0) {
 				n--;
 				s++;
+				d <<= 4;
+				d |= h;
 			}
 		}
-		rx_params[p++] = (h<<4) | d;
+		rx_params[p++] = d;
+		DEBUG_POKE(rxhex, d);
 	}
+	if (!n || *s != '\n')
+		p = 0;
+	DEBUG_POKE(rxpar, p);
+	return p;
+}
 
-	if (n && *s != '\n')
+#else
+
+static inline
+uint8_t parse_rx_params(uint8_t *s, uint8_t n)
+{
+	uint8_t p;
+	__asm__("\n"
+		"1:					\n"
+		"	clr	%[p]			\n"
+		"	tst	%[n]			\n"
+		"	breq 8f				\n"
+		"	ldi	r26, lo8(rx_params)	\n"
+		"	ldi	r27, hi8(rx_params)	\n"
+		"2:					\n"
+		"	ld	r21, Z+			\n"
+		"	cpi	r21, ' '		\n"
+		"	breq 6f				\n"
+		"	cpi	r21, '\\n'		\n"
+		"	breq 8f				\n"
+		"	rcall	nibble			\n"
+		"	brcc 7f				\n"
+		"	mov	r25, r21		\n"
+		"	subi	%[n], 1			\n"
+		"	breq 7f				\n"
+		"	ld	r21, Z			\n"
+		"	rcall	nibble			\n"
+		"	brcc 5f				\n"
+		"	subi	%[n], 1			\n"
+		"	breq	7f			\n"
+		"	adiw	r30, 1			\n"
+		"	swap	r25			\n"
+		"	or	r25, r21		\n"
+		"5:					\n"
+		"	cpi	%[p], 8	; sz rx_params	\n"
+		"	brcc 7f				\n"
+		"	subi	%[p], -1		\n"
+		"	st	X+, r25			\n"
+#ifdef DEBUG
+		"	sts	debug_data + 6, r25	\n"
+		"	sts	debug_data + 9, %[p]	\n"
+#endif
+		"	rjmp 2b				\n"
+		"					\n"
+		"nibble:				\n"		
+		"	subi	r21, '0'		\n"
+		"	cpi	r21, 10			\n"
+		"	brcs 9f				\n"
+		"	subi	r21, 'a'-'0'		\n"
+		"	cpi	r21, 6			\n"
+		"	brcc 9f				\n"
+		"	subi	r21, -10		\n"
+		"	sec				\n"
+		"9:	ret				\n"
+		"					\n"
+		"6:					\n"
+		"	subi	%[n], 1			\n"
+		"	brne 2b				\n"
+		"7:					\n"
+		"	clr	%[p]			\n"
+		"8:					\n"
+		: [p] "=a" (p), // r24      (r16…)
+		  [s] "+z" (s), // r30,r31
+		  [n] "+a" (n)  // r22      (r16…)
+		: : "r21", "r25", "r26", "r27"
+		);
+	DEBUG_POKE(rxpar, p);
+	return p;
+}
+#endif
+
+void parse_command(uint8_t *s, uint8_t n)
+{
+	if (!n || n >= 15)
 		goto fail;
-	
-	uint8_t *a = (uint8_t *)(((uint16_t)rx_params[0] << 8) | rx_params[1]);
 
-	if (cmd == 'C' && p >= 2 && rx_params[0] + p <= sizeof(struct config))
+	uint8_t cmd = *s++;
-		memcpy((uint8_t*)&config + rx_params[0], rx_params+1, p-1);
+	uint8_t p = parse_rx_params(s, n-1);
+	uint8_t *pp = rx_params;
+
+	uint8_t *a = (uint8_t *)(((uint16_t)pp[0] << 8) | pp[1]);
+
+	if (cmd == 'R' && p==1) 
+		__asm__("\n"
+			"	ldi	r18, 1		\n"
+			"	out	%[ccp], %[p]	\n"
+			"	sts	%[swrr], r18	\n"
+			:
+			: [p]    "r" (pp[0]),
+			  [ccp]  "n" (_SFR_IO_ADDR(CCP)),
+			  [swrr] "n" (&RSTCTRL.SWRR)
+			: "r18"
+			);
+
+	if (p >= 3 && p < 8 && (
+		    cmd == 'C' && pp[0]==0xba
+		    || cmd == 'E'
+		    || cmd == 'U')) {
+		uint8_t *e = (uint8_t*) &config;
+		if (cmd=='E')
+			e = (uint8_t*) EEPROM_START;
+		if (cmd=='U')
+			e = (uint8_t*) &USERROW;
+		e += pp[1];
+		pp[p] = *e;
+		memcpy(e, pp+2, p-2);
+		if (cmd != 'C')
+			__asm__("\n"
+				"	ldi	r24, %[erwp]	\n"
+				"	out	%[ccp], %[p]	\n"
+				"	sts	%[ctrl], r24	\n"
+				:
+				: [p]    "r" (pp[0]),
+				  [ccp]  "n" (_SFR_IO_ADDR(CCP)),
+				  [ctrl] "n" (&NVMCTRL.CTRLA),
+				  [erwp] "n" (NVMCTRL_CMD_PAGEERASEWRITE_gc)
+				: "r24"
+				);
+	}
+	else if (cmd == 'T' && p==1) {
+		immediate += pp[0];
+		pp[1] = immediate;
+	}
 	else if (cmd == 'M' && p==2) {
-		rx_params[2] = *a;
+		pp[2] = *a;
-		p++;
 	}
 	else if (cmd == 'W' && p==3) {
-		rx_params[3] = *a;
+		pp[3] = *a;
-		*a = rx_params[2];
+		*a = pp[2];
-		p++;
+	}
+	else if (cmd == 'K' && p==4) {
+		cli();
+		pp[4] = clock_tick;
+		clock = *(uint32_t*)pp;
+		sei();
+	}
+	else if (cmd == 'D' && p==1) {
+		pp[1] = test_calib;
+		test_calib = pp[0];
 	}
 	else
 		goto fail;
 
 	send_char('R');
 	send_char('!');
-	send_hex(cmd, rx_params, p, 1);
+	send_hex(cmd, pp, p+1, 1);
 	return;
 fail:
 	send_str("R?\n");

src/rtc.c

@@ -4,6 +4,7 @@
 
 // !!! int = int8_t
 
+#include "bate.h"
 #include "rtc.h"
 
 #include <avr/io.h>
@@ -32,6 +33,11 @@ ISR(RTC_PIT_vect, ISR_NAKED)
 	__asm__ ("push r24"            "\n\t"
 		 "in r24, __SREG__"    "\n\t"
 		 "push r24"            "\n\t"
+#ifdef DEBUG
+		 "lds r24, debug_data+9"	"\n\t"
+		 "subi r24, -1"			"\n\t"
+		 "sts debug_data+9, r24"	"\n\t"
+#endif
 		 "ldi r24,1"           "\n\t"
 		 "sts %[flag], r24"    "\n\t"
 		 "sts %[tick], r24"    "\n\t"

src/uart.c

@@ -57,7 +57,17 @@ uint8_t uart_tick()
 	return r;
 }
 
+// `uart_tx` buffer size must be a power of 2, max 256.
+// Fix `tx()` and `put_char()` / `put_char:`
+// when the size changes.
+// For now, we can afford half of the available RAM,
+// and still have 128 bytes for the stack
+#ifdef UART_TX_SMALL
 uint8_t uart_tx[128];
+#else
+uint8_t uart_tx[256];
+#endif
+
 #define uart_tx_m (sizeof(uart_tx) - 1)
 volatile uint8_t uart_tx_w;
 volatile uint8_t uart_tx_r;
@@ -124,7 +134,9 @@ void tx()
 		"1:							\n"
 		"	mov	r30, r21	;			\n"
 		"	subi 	r21, 0xff	; r++ & uart_tx_m	\n"
+#ifdef UART_TX_SMALL
 		"	andi	r30, 0x7f	;			\n"
+#endif
 		"	ldi 	r31, 0					\n"
 		"	subi 	r30, lo8(-(uart_tx))			\n"
 		"	sbci	r31, hi8(-(uart_tx))			\n"
@@ -238,9 +250,6 @@ ISR(USART0_RXC_vect, ISR_NAKED)
 		"	subi 	r24, -1				\n"
 		"	sts 	debug_data + 4, r24		\n"
 #endif
-		"	lds	r24, %[STATUS]	 		\n"
-		"	sbrs	r24, %[RXCIF]			\n"
-		"	rjmp 1f					\n"
 		"	lds 	r24, %[RXDATA]	 		\n"
 		"	lds 	r30, uart_rx_w			\n"
 		"	ldi 	r31, 0		 		\n"
@@ -251,7 +260,8 @@ ISR(USART0_RXC_vect, ISR_NAKED)
 		"	sts 	debug_data + 5, r24		\n"
 #endif
 		"	subi	r30, lo8(uart_rx)		\n"
-		"	sbrs 	r30, 4		  		\n"
+		"	sbrc 	r30, 4 ; log2(sizeof(uart_rx))	\n"
+		"	subi	r30, 1				\n"
 		"	sts 	uart_rx_w, r30			\n"
 		"	cpi 	r24, '\n'	 		\n"
 		"	brne 1f			 		\n"
@@ -266,15 +276,11 @@ ISR(USART0_RXC_vect, ISR_NAKED)
 		"	out	__SREG__, r24			\n"
 		"	pop	r24				\n"
 		"	reti					\n"
-		:
+		: : [RXDATA] "n" (&USART0.RXDATAL)
-		: [STATUS] "n" (&USART0.STATUS),
-		  [RXCIF]  "n" (USART_RXCIF_bp),
-		  [RXDATA] "n" (&USART0.RXDATAL)
 		);
 }
 #endif
 
-
 #if 0
 // These are implemented in `uart_tx.S`
 

src/uart_tx.S

@@ -1,3 +1,6 @@
+//
+// uart_tx.S
+//
 // avoid quite a few push and pops and jumps
 
 	.global send_hex_word
@@ -9,7 +12,7 @@
 	.global send_eol
 	.global	command
 
-// `tx()` and `put_char()` do not gobble r18, r20, r23, r23, r26, and r27.
+// `tx()` and `put_char()` do not gobble r18, r20, r22, r23, r26, and r27.
 	
 put_char:
 	// non-global, non-C
@@ -19,9 +22,13 @@ put_char:
 	ldi	r19, 1
 	add	r19, r30
 	eor	r23, r19
+#ifdef UART_TX_SMALL
 	andi	r23, 0x7f // uart_tx_m
 	breq 1f
 	andi 	r30, 0x7f // uart_tx_m
+#else
+	breq 1f
+#endif
 	ldi	r31, 0
 	subi 	r30, lo8(-(uart_tx))
 	sbci 	r31, hi8(-(uart_tx))
@@ -116,7 +123,7 @@ command:
 	breq 9b
 	ldi	r22, 'R'
 	rcall	send_char22
-	ldi	r22, ' '
+	ldi	r22, '>'
 	rcall	send_char22
 	ldi	r26, lo8(uart_rx)
 	ldi	r27, hi8(uart_rx)
@@ -125,19 +132,12 @@ command:
 	ld	r22, X+
 	call	send_char22
 	subi	r18, 1
-	brcc	1b
+	brne	1b
-	cpi	r22, '\n'
-	breq 2f
-	rcall	send_eol
-	clz
-2:
 	ldi	r24, lo8(uart_rx)
 	ldi	r25, hi8(uart_rx)
 	mov	r22, r20
 	push	r20
-	breq 3f
 	rcall	parse_command
-3:	
 	pop	r24
 rx_dismiss:
 	cli
@@ -170,4 +170,5 @@ rx_dismiss:
 	sts	uart_rx_mes, r20
 	sts	uart_rx_w, r19
 	sei
+9:
 	ret