A Scheme Interpreter for ARM Microcontrollers:
ChangeLog for Snapshot 00.0250

Changes from snapshot 00.0241:

• This snapshot supports 2 new boards: the STM32-LCD from Olimex and the Overo Tide from Gumstix (with Thumbo carrier board).


• Write functions have been modified to no longer automatically write spaces (or spaces + back-spaces) after tokens and expressions. This corrects a bug whereby libraries could not be imported from within a flash file without applying an ugly kludge when the file was written (i.e. the library name had to be written character by character to avoid the space+back-space problem). An important implication of this modification (coupled with limitations in the reader and parser) is that, now, spaces (or newlines) have to be explictly written to file between top-level expressions (eg. using (write-char #\space port) or (display #\space port) or (newline port)) so that the reader can properly identify the end of such expressions when they are re-obtained from a file. A last-minute modification was applied on June 18, 2011 to partially mitigate this.


• FAT16 SD-card support has been integrated in the system. Communication with the cards is initialized with (sd-init) after which the SDFT port-model can be used for opening input and output files on such cards. The list of boards assembled with this support is provided at the end of this Log. Support is limited to cards of 2 GB or less, 8.3 file names, and only the top directory of the card. The display of file names (and directories) obtained from (files SDFT) has been improved relative to the library-based implementation in 00.0241.


• System 0 and Linker library functions are now integrated in the system, including such functions as register-copy-bit, register-copy-bit-field, defined?, link, unpack-to-lib, unpack-above-heap, libs, erase-libs, config-pin, config-power, pin-set and pin-clear among others (cf. common/armpit_scheme_library.s and mcu_specific/*/*_system_0.s).


• R6RS functions related to bytevectors and bitwise operations have been moved to common/armpit_scheme_r6rs_library.s and fixnum functions have been added there (fx+, fx-, fx/, fx*, fx=?, fx$>$?, fx?, fx$>$=?, fx=?, fxmax, fxmin). Fixnum functions are included only if the corresponding flag is set in armpit_00.0250.s.


• The OMAP3530 version (TI-Beagle and Overo Tide) is now a Live-SD version that boots from SD-card, runs from POP RAM, with the heap in POP RAM, and does not touch POP flash. Installation instructions have been updated accordingly in the "How To: upload, ..." page.


• USB Device functionality has been added to the TI-Beagle.


• Floating point coprocessors are now enabled (and used) on the OMPA3530 boards and on the CS-EP9302.


• The evaluator has been modified to use type-based jump tables and inlined cons/save operations are now generally limited to this core area. This modification freed up space for other functions while maintaining system performance. Additionally, the dispatch on number of input arguments has been unrolled to improve performance.


• Procedure tags (full tags beyond the low 8-bits) have been extended to contain possible default startup values (for sv4) and common startup pre-functions.


• The robustness of the parser has been slightly improved by checking for a valid bottom to the parse stack.


• A bug in the alignment of semi-spaces in stop-and-copy gc has been fixed (cf. common/armpit_as_constants.s).


• Landing pad sizes (eg. for the call macro) have been tightened on cortex-m3 MCUs.


• The interrupt number used to identify Systick interrupts on cortex-m3 MCUs has been changed from 255 to 64.


• On STM32x MCUs, the i2c subsystem has been improved to make it possible to read the accelerometer of the STM32-LCD.


• On the AT91SAM7 and STR711, buffers now start higher in RAM to provide additional space for stack-pointer slippage. Additionally, the AT91SAM7 isr exit has been made identical to that of the STR711.


• On the CS-EP9302 and STM32-H103, the boot override function is now performed by the onboard user button rather than by a separate pin.


• Miscellaneous other source code adjustments have been performed to maintain or enhance the compact size, functionality and performance of the system.


• Where appropriate, program examples are under development to illustrate the application of the new features described above.


• Whether SD-card support is assembled into the distribution is listed below, along with connection type (either: on-board connector, or SPI interface and CS pin) (note: on LPC-H2214/94, connect P0.7 to 3.3 Volts):

  Board	SD-card	Board	SD-card
  SAM7_H256	SPI0, CS=PA.10	CS_E9302	on-board (spi)
  EVB_LM3S1968		EVB_LM3S6965	on-board (spi)
  IDM_LM3S1958	on-board (spi)	LPC_P1343
  Blueboard_1768	SPI0, CS=P0.16	LCDDemo_2158
  LPC2478_STK	on-board (mci)	LPC_H2103
  LPC_H2148		LPC_H2214	SPI0, CS=P0.20
  LPC_H2294	SPI0, CS=P0.20	SFE_Logomatic1	on-board (spi)
  SFE_Logomatic2	on-board (spi)	TINY_2106
  TINY_2131		TINY_2138
  LPC_H2888		TI_Beagle	on-board (mci)
  TCT_Hammer	on-board (spi)	STM32_DT_Board
  STM32_H103	SPI1, CS=PA.8	STR_H711	BSPI1, CS=P1.9
  STR91X_M		STM32_LCD	on-board (mci)
  GMX_OVERO_TIDE	on-board (mci)



• The read buffer sizes configured in mcu-specifc header files (variable name: RBF_size) of this snapshot are given below. Subtract 4 bytes from these values to identify the number of characters that the buffer can hold (eg. 2KB means space for: 2048 - 4 = 2044 characters).

  Board	Buffer Size	Board	Buffer Size
  SAM7_H256	2 KB	CS_E9302	64 KB
  EVB_LM3S1968	2 KB	EVB_LM3S6965	2 KB
  IDM_LM3S1958	2 KB	LPC_P1343	1 KB
  Blueboard_1768	4 KB	LCDDemo_2158	4 KB
  LPC2478_STK	28 KB	LPC_H2103	1 KB
  LPC_H2148	4 KB	LPC_H2214	16128 Bytes
  LPC_H2294	16128 Bytes	SFE_Logomatic1	2 KB
  SFE_Logomatic2	4 KB	TINY_2106	2 KB
  TINY_2131	1 KB	TINY_2138	2 KB
  LPC_H2888	128 KB	TI_Beagle	64 KB
  TCT_Hammer	64 KB	STM32_DT_Board	2 KB
  STM32_H103	1536 Bytes	STR_H711	2 KB
  STR91X_M	2 KB	STM32_LCD	2 KB
  GMX_OVERO_TIDE	64 KB



• The status of in-core I2C support for all MCUs is shown below (this is the high-level support, including interrupts, needed for remote-execution oriented multi-processing). For the TINY-2131, LPC-H2103 and LPC-P1343, this support is not assembled into the distribution.

  Board	I2C Support	Board	I2C Support
  SAM7_H256	yes	CS_E9302
  EVB_LM3S1968		EVB_LM3S6965
  IDM_LM3S1958		LPC_P1343	yes
  Blueboard_1768	yes	LCDDemo_2158	yes
  LPC2478_STK	yes	LPC_H2103	yes
  LPC_H2148	yes	LPC_H2214	yes
  LPC_H2294	yes	SFE_Logomatic1	yes
  SFE_Logomatic2	yes	TINY_2106	yes
  TINY_2131	yes	TINY_2138	yes
  LPC_H2888		TI_Beagle
  TCT_Hammer		STM32_DT_Board	yes
  STM32_H103	yes	STR_H711	yes
  STR91X_M	yes	STM32_LCD	yes
  GMX_OVERO_TIDE



• A last-minute modification was made to the reader/parser to mitigate the need for explicit spaces (or newlines) to be inserted between top-level expressions in files (especially scheme code files) at file writing time. A new label named rdexp4:, and two branches to that label, were added in the file common/armpit_scheme_read_write.s. This added code is used to consider the closing parenthesis and the double-quote as valid ends for expressions read from file (i.e. for ports where a cr or lf is not needed to terminate an expression). The intent is that if a file contains top-level expressions that end in a closing parenthesis or double-quote and these top-level expressions are not separated by spaces or newlines, they will still be read correctly. An example would be: (+ 1 2)(- 4 5)"wawa"(- 2 6)"zig""zag". This is meant particularily as a convenience for cases where a file to be read contains only lists, strings and other such explicitly-delimited expressions at its top-level which should be the case for a code file, for example, where all top-level expressions would be lists such as: (define lprt gio3)(config-pin 1 5 #b01) .... Writing such code to file should not require the explicit addition of spaces or newlines between each top-level expression (that would have been required in 00.0250 before the modification was applied). The modification is not smart enough to identify an opening parenthesis, semi-colon or double-quote (i.e. characters starting a new top-level expression) as indicating the end (+ 1 char position) of the current expression. Accordingly, it is not able to read: 1000(+ 3 4) or 1000"wawa" from file as 2 separate expressions (1000 and (+ 3 4) or 1000 and "wawa"). In this case, after writing 1000 to file, and before writing (+ 3 4) or "wawa", one still has to write-char or display a #\space or newline to the file such that 1000 is properly re-extractable as a separate expression. No unforseen problematic issues are expected to arise from this code change but, just in case, instructions on how to revert the modification are provided in the source code, within common/armpit_scheme_read_write.s near label rdexp4: (9 lines to comment-out, and 2 commented lines to swap), and, for the LPC-1343, near the top of the LPC_13xx_usb.s file (.space directives).

Last updated June 18, 2011