1. 328eForth for Arduino Uno
C. H. Ting
February 16, 2012
SVFIG

2. Summary Optimized FORTH for Arduino Uno ATmega328P
Assembly Code of 328eForth
AVR Studio 4 Tool Suite
Assembling 328eForth
HyperTerminal
Demo of 328eForth
Optimized Flash Programming
Conclusion

3. Optimized Forth for Arduino
Subroutine Thread Model
Fully optimized
Uniform byte addressing
Case insensitive
Interpreter is in Bootloader section
Optimized flash programming
Visible words are reduced to 140 for ease of learning

4. ATmega328P 8 Bit microcontroller, 131 instructions 20 MIPS at 20 MHz
32KB Flash, 2 KB RAM, 1 KB EEPROM
3 Counter/Timers
6 Channels 10-bit ADC
USART, SPI, I2C, ISP
23 Programmable I/O lines V

5. Assembly Code of 328eForth
Reset and interrupt vectors
Assembly macros
Kernel of primitive commands
Compound commands
Common utilities
Interpreter
Compiler
Programming tools
RAM memory
CPU and IO registers
System Variable
Buffers and stacks

6. AVR Studio 4 Tool Suite AVR Assembler 2 AVR Simulator 2
In System Programming with AVRISP mkll
Configuration of Atmega328 chip

7. Assembling 328eForth Assembling by AVR Assembler 2
Simulating by AVR Simulator 2
In System Programming with AVRISP mkll
Running 328eForth from HyperTerminal

8. HyperTerminal Arduino 0022 supplies USB to UART driver
19,200 Baud, 8 data bits, 1 stop bit, no parity, no flow control
900 ms delay after sending each line of text
Send Text File option to download file to Uno

9. Demo of 328eForth Turn LED on and off HEX
20 24 C! ;set Pin 13 as output
20 23 C! ;toggle Pin 13
Turn beeper on and off
40 2A C! ;set Pin 6 as output
42 44 C! ;set Timer0 CTC mode
FF 47 C! ;maximum count for Timer0
3 45 C! ;prescaler=3, start beeper
0 45 C! ;prescaler=0, stop beeper

10. Demo of 328eForth HEX : TEST1 1 2 3 4 5 ; : TEST2 IF 1 ELSE 2 THEN . ;
: TEST3 10 FOR . NEXT ;
: TEST4 CR .” HELLO, WORLD!” ;
: TEST5 FOR FFFF FOR NEXT NEXT ;

11. Optimized Flash Programming
Flash memory in ATmega328 can endure 10,000 programming cycles.
Flash programming must be optimized.
Two 128 byte buffers are allocated to store data before writing into flash memory.
Ping-Pong algorithm minimizes flash programming.

12. Ping-Pong Algorithm for Read
If data is in New Buffer, go to 6.
If data is in Old Buffer, go to 5.
If Old Buffer was modified, write data to flash
Fill Old Buffer with new data from flash
Switch New and Old Buffers.
Read data from New Buffer.

13. Ping-Pong Algorithm for Write
If address is in New Buffer, go to 6.
If address is in Old Buffer, go to 5.
If Old Buffer was modified, write data to flash
Fill Old Buffer with new data from flash
Switch New and Old Buffers.
Write data to New Buffer and mark it as modified.

14. Conclusion ISP is very pleasing.
Ping-pong flash buffers optimize flash programming.
2.1 us per empty FOR-NEXT loop at 16 MHz.
ATmega328P is forced to be compatible with eForth.