Spiffy PIC Programmer

Updated 1999-12-15

Added documentation on 1999-12-15

Goals

This is a work in progress, so not all of the goals have been realized yet, and the page has not been properly organized. It doesn't even program PICs right now, but it has progressed to attempting to program PICs.

Ability to program all PICs described in Microchip's EEPROM Programming Specification documents DS30262B and DS39025B
- PIC16F83
- PIC16F84
- PIC16F84A
- PIC16F873
- PIC16F874
- PIC16F876
- PIC16F877
- Other PICs with the same programming interface
RS-232 style serial interface
- Human usable protocol
- Can be used from a terminal program
- Requires RTS/CTS flow control
Not dependent on serial port voltages to program the target PIC
Optional production quality programming support
- Covers voltage range for the extended voltage PICs.
- Software selectable supply voltage for the target PIC between 0v and 10v with 8-bit resolution
- User can calibrate voltages; values can be stored in EEPROM
- Support can be omitted to make a simpler programmer
Intel 8-bit Hex file input interpreted in programmer's firmware
Status indicator LEDs

Status

Documentation -- Just lacks the circuit. Any good Linux software for drawing those?
RS-232 link works
- Data timings
- CTS flow control
  - Some terminal programs do not properly implement RTS/CTS flow control, even when hardware support exists.
  - Programmer's use of CTS to slow the sending of data from the computer works with good terminal software.
- DTR -- resets the programmer properly.
- DSR -- always on.
- CD
  - Connected to the power LED output to avoid use of another RS-232 transmitter on a MAX232 like device.
  - The low voltage (0v) for the false state is out of RS-232C specs, but works with most hardware anyway.
Programmer responds to commands given from terminal program
Testing with actual target PICs
- The expected data is being output.
  - HEX file input works.
- I have no tools to see the actual clock and data output.
- Target does not respond to verify command. It may also not respond to the program command.

Possible spinoff: Self-contained portable programmer

The programmer could be modified to get its instructions from a serial EEPROM instead of an RS-232 link. The result could be a small portable programmer that can reprogram flash ROM PICs with prewritten and prepared software. The user interface would only need indicator LEDs, which are already part of the design spec, a reset button to reset the programmer and target, and a replaceable EEPROM.

Detailed Specifications

These specifications are meant primarily as internal documentation for now. The contents are not completely accurate and are subject to change. The contents are normally within a few days of my development progress.

Programmer PIC pin connections

Programmer PIC16F84	Connection to	Input or Output	Function
!MCLR, pin 4	RS-232 DTR	Input	Reset for the programmer. When a terminal program connects to the programmer, it should allow the programmer to start.
RA0, pin 17	Green LED annode	Output	Programmer running indicator
RA1, pin 18	Yellow LED annode	Output	Program or verify operation in progress indicator
RA2, pin 1	RS-232 RD	Output	Sends data to the computer
RA3, pin 2	RS-232 TD	Input	Receives data from the computer
RA4, pin 3	RS-232 CTS	Output	Hardware flow control connection to RS-232. It allows the programmer to keep the computer from sending data while processing the data and programming.
RB0, pin 6	Connection to !CS on serial DAC	Output	Used to operate the 8-bit serial DAC that controls the variable V_DD of the target PIC.
RB1, pin 7	Clock for serial DAC	Output	Synchronous serial clock for the 8-bit serial DAC that controls the variable V_DD of the target PIC.
RB2, pin 8	Data for serial DAC	Output	Data to operate the 8-bit serial DAC that controls the variable V_DD of the target PIC.
RB3, pin 9	Hardware switch for programming voltage	Output	Applies programming voltage to the !MCLR pin of the target PIC. It is used to reset the target during programming.
RB4, pin 10	Red LED annode	Output	Error indicator
RB5, pin 11	Unused	Output
RB6, pin 12	RB6 on target PIC	Output	Clock input for the target PIC. A voltage conversion device may need to be between the two PICs.
RB7, pin 13	RB7 on target PIC	Input and Output	Data I/O to the target PIC. A voltage conversion device may need to be between the two PICs.

RS-232 serial to programmer PIC table

RS-232 Name	25 Pin RS-232	9 Pin RS-232	PIC16F84 (Programmer)	Function
CTS	5	8	RA4, pin 3	Allows the programmer to use hardware RTS/CTS flow control. While programming another PIC, the programmer will use this connection to make the computer suspend sending data by brining the line low. When the programmer can receive more data, it will raise the line.
DTR	20	4	!MCLR, pin 4	This line is normally brought high to tell a device on the other end to pick up, and is brought low when the program wants to terminate communication. It'll do about the same by resetting the programmer when low. When a terminal program connects to the programmer, it should allow the programmer to start.
RD	3	2	RA2, pin 1	Asynchronous serial data output from the programmer.
TD	2	3	RA3, pin 2	Asynchronous serial data input to the programmer.

Programmer to target PIC voltage level conversion

Use voltage comparator to to raise anything above 1v to supply voltage
Use buffer (CMOS 4000 series?) to bring down voltage
Schmitt triggers may be needed

Computer command protocol

On power up, the programmer sends an identification string with version number.
The prompt, ">" is displayed when the programmer is ready to accept a command.
A single character command is entered by the computer. No newline or return characters should be sent.
If the command character is a colon (":"), more characters from the computer will be expected. See the data command for more information.
If an error occurs, the programmer responds with "error" and a short description. See the error code section for more information. The error message is followed with a newline character.
After completing the command, the programmer loops back to the prompt from part 2 of this list.

Alpha version limitations

Unless the programmer can reset the target:
- EEPROM data may have to proceed the config data in the HEX file.
- The HEX file must include all data in order of increasing address, except for EEPROM data.
No check is performed to see if the specified address should be written to.
- No data should be specified for the reserved config addresses 0x2004 through 0x2006.
- Program data should be within the available ROM space of the target.
Error addresses reported for EEPROM are not unique to EEPROM.

Final version limitations

No check is performed to see if the HEX file is suitable for the target part.
The programmer will be able to report a part ID from the target, but it will not match the ID with a part name, like PIC16F877, and cannot inspect the HEX file to see what part it was made for (the format specifies no way to do this). These tasks are left to other software.
Each line of the HEX file may specify program data, config data, or EEPROM data. A line cannot specify any combination of the kinds of data.

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