Newbie problems

© MCS Electronics, 1995-2007

DDRB = &B1111_0000 ' upper nibble is output, lower nibble is input

SET PORTB.7 'will set the MS bit to +5V

RESET PORTB.7 'will set MS bit to 0 V

To read a pin :

Print PINB.0 'will read LS bit and send it to the RS-232

You may also read from PORTx but it will return the value that was last written to it.

To read or write whole bytes use :

PORTB = 0 'write 0 to register making all pins low

PRINT PINB 'print input on pins

I want to write a special character but they are not printed correct:

Well this is not a newbie problem but I put it here so you could find it.

Some ASCII characters above 127 are interpreted wrong depending on country settings. To print the right value use : PRINT "Test{123}?"

The {xxx} will be replaced with the correct ascii character.

You must use 3 digits otherwise the compiler will think you want to print {12} for example. This should be {012}

My application was working but with a new micro it is slow and print funny

Most new micro’s have an internal oscillator that is enabled by default. As it runs on 1 or 4 or 8 Mhz, this might be slower or faster then your external crystal. This results in slow operation.

As the baud rate is derived from the clock, it will also result in wrong baud rates.

Solution : change frequency with $crystal so the internal clock will be used. Or change the fuse bits so the external xtal will be used.

Some bits on Port C are not working

Some chips have a JTAG interface. Disable it with the proper fusebit .

Tips and tricks

This section describes tips and tricks received from users.

Kyle Kronyak : Using all the RAM from an external RAM chip.

I have found a way to use the 607 bytes of external SRAM that are normally not available when using hardware SRAM support with BASCOM-AVR. It's actually quite simple. Basically the user just has to disconnect A15 from /CE on the SRAM module, and tie /CE to ground. This makes the chip enabled all the time. Addresses 1-32768 will then be available! The reason is because normally when going above 32768, the A15 pin would go high, disabling the chip. When A15 is not connected to /CE, the chip is always enabled, and allows the

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© MCS Electronics, 1995-2007

address number to "roll over". Therefore address 32162 is actually 0, 32163 is actually 1, 32164 is actually 2, etc. I have only tested this on a 32k SRAM chip. It definitely won't work on a 64k chip, and I believe it already works on any chip below 32k without modification of the circuit.

Programming problems

-When you have unreliable results, use a shielded LPT cable

-The AVR chips have a bug, if the erase is not complete. It tend's to hang at some point. Sometimes although the system reports erased but blank check report "not empty". As per Atmel Data Errata You must drop the vcc by 0.5V ( a diode 1N4148 in Series ) if the erase is not happening. ( Such Chip's are unreliable and hence can be used only if you are sure ). This can happen after you have programmed the chip many times

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ASCII chart

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