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recipes/arduinouno/at28: improve reliability
Previously, it could never write more than a few bytes before pingpong getting a mismatch error. Now, I can pingpong Collapse OS binary without a mismatch.
This commit is contained in:
Virgil Dupras
parent
bc1cc591ce
commit
b8e52707e9
@ -14,10 +14,10 @@ all: $(TARGET)
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@echo Done!
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send: $(PROGNAME).hex
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avrdude $(AVRDUDEARGS) -p $(AVRDUDEMCU) -U flash:w:$<
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avrdude $(AVRDUDEARGS) -p $(AVRDUDEMCU) -U flash:w:$(PROGNAME).hex
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$(TARGET): at28wr.asm
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$(AVRA) -o $@ at28wr.asm
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$(TARGET): $(PROGNAME).asm
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$(AVRA) -o $@ $(PROGNAME).asm
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clean:
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rm -f $(TARGET) *.S.eep.hex *.S.obj
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@ -23,6 +23,11 @@ on the Arduino's right side (except for VCC, which needs to be wired).
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PD0 and PD1 are not used because they're used for the UART.
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AT28 selection pins are pulled up to avoid accidental writes due to their line
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floating before Arduino's initialization.
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I've put 1uf decoupling caps next to each IC.
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## Software
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The software in at28wr.asm listens to the UART and writes every byte it receives
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@ -8,6 +8,17 @@
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; with PD7:2 for bits 7:2 and PB1:0 for bits 1:0 (PD1 and PD0 are used for
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; UART).
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;
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; *** Timing, matching and CE ***
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;
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; A lot of trial-and-errors went into those NOPs being place to give time for
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; latching. All these timing are well, well above maximums given in the specs,
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; but when I wasn't going well, well above those specs, I was experiencing
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; read/write errors. It seems we live in an imperfect world!
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;
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; I'm also not sure, in "writedata", whether toggling CE along with WE is
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; actually needed, but until I did, I was experiencing random write failures.
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; So, we end up with this...
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;
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; *** Register Usage ***
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;
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; r0: holds whether last received char was tty-escaped (0 = no, 1=yes)
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@ -92,6 +103,10 @@ sendaddr:
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; send r20 to EEPROM's I/O7:0 through PD7:2 and PB1:0
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writedata:
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cbi PORTB, FLCE
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; addr is latched on WE falling edge
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cbi PORTB, FLWE
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; send bits 7:2
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mov r16, r20
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andi r16, 0xfc
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@ -106,49 +121,59 @@ writedata:
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andi r17, 0xfc
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or r16, r17
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out PORTB, r16
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; data is latched on rising edge
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sbi PORTB, FLWE
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sbi PORTB, FLCE
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nop ; Give the AT28 time to latch
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nop
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nop
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ret
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; push r20 to the rom and increase the memory counter
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pushdata:
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nextaddr:
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; first, set up addr
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mov r23, r21
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rcall sendaddr
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mov r23, r22
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rcall sendaddr
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inc r22
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brne pushdata_0 ; no overflow? skip
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brne nextaddr_0 ; no overflow? skip
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inc r21
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pushdata_0:
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; addr is latched on WE falling edge
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cbi PORTB, FLWE
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; now, lets set up data. Plenty enough instructions to ensure a 100ns
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; minimum delay.
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rcall writedata
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; data is latched on rising edge
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sbi PORTB, FLWE
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nextaddr_0:
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ret
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; wait until I/O7 stops toggling
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waitio7:
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cbi PORTB, FLCE
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cbi PORTB, FLOE
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nop ; Give the AT28 time to latch
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nop
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nop
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in r16, PIND
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sbi PORTB, FLOE
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sbi PORTB, FLCE
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andi r16, 0xfc
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cbi PORTB, FLCE
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cbi PORTB, FLOE
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nop ; Give the AT28 time to latch
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nop
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nop
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in r17, PIND
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sbi PORTB, FLOE
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sbi PORTB, FLCE
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andi r17, 0xfc
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cp r16, r17
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brne waitio7
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ret
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; read EEPROM's I/O7:0 through PD7:2 and PB1:0 and put result in r20.
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; read EEPROM's I/O7:0 through PD7:2 and PB1:0 into r20
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readdata:
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cbi PORTB, FLCE
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cbi PORTB, FLOE
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nop ; Give the AT28 time to latch
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nop
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nop
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; read bits 7:2
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in r20, PIND
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andi r20, 0xfc
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@ -157,13 +182,14 @@ readdata:
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andi r16, 0x03
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or r20, r16
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sbi PORTB, FLOE
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sbi PORTB, FLCE
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ret
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; Set PD7:2 and PB1:0 to output
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ioout:
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ldi r16, 0xfc ; PD7:2
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out DDRD, r16
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ldi r16, 0x3f ; PB5:0 (WE, OE and CE too)
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ldi r16, 0x3f ; PB5:0 (CP, WE, OE and CE too)
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out DDRB, r16
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ret
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@ -181,11 +207,9 @@ main:
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ldi r16, high(RAMEND)
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out SPH, r16
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; We begin with WE and OE disabled (high), but CE stays enabled (low)
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; the whole time.
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sbi PORTB, FLWE
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sbi PORTB, FLOE
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cbi PORTB, FLCE
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sbi PORTB, FLCE
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; Clear counters and flags
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clr r0
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@ -204,7 +228,8 @@ main:
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loop:
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rcall uartrd
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rcall ioout
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rcall pushdata
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rcall nextaddr
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rcall writedata
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rcall ioin
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rcall waitio7
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rcall readdata
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@ -12,7 +12,7 @@ properly set up, TTY-wise. You'll probably want to do that with `stty`. The tool
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itself takes care of setting the regular stuff (`cs8`, `-parenb`, etc), but you
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need to set the speed. Here's an example working on OpenBSD:
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$ ( stty 115200 ; ./upload - a000 os.bin ) <>/dev/cuaU0
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$ ( stty 115200 raw ; ./upload - a000 os.bin ) <>/dev/cuaU0
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To be honest, I'm having a bit of troubles making these tools work as well on
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OpenBSD as they do in Linux. But it *does* work. Here are some advices:
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