DSP SSTC Controller

This is a project for a versatile, digital signal processor (DSP) based generic driver and controller circuit for Solid State Tesla Coils (SSTCs). Support for all new topologies (DRSSTC, OLTC, PLL-SSTC, ...) can be implemented programmatically. The same controller can serve to debug switch mode supplies, by functioning as a PWM signal generator. This DSP controller board will use one of Motorola/Freescale's miniature hybrid controllers of the 56800E series (56F8322, datasheet). These are very small microcontrollers with a DSP core, running 60 MHz with 60 MIPS (17ns per instruction). The 56F8322 is preferred to others of the 56800E series as it has an on-board 6-channel PWM module and 6 timers, and is on Sample Order status. The final version of the DSP board will allow you to:
The optical serial communication link is achieved with a relatively cheap TFDU/TFDS/TFDT4100 IrDA transceiver module being 'mis-used' for normal serial data bit encoding instead of the IrDA pulse-length encoding. The TFDU4100 has an internal transmitter diode with drive circuitry, and a receiver diode with gain control and amplifier for digital output, so it is simpler to use the module than a bunch of discretes. The PC side will need a second TFDU4100, plus some small circuitry to convert to 0V and 5V (never mind the 'official' RS-232 signal levels :-).
The board output lines are driven by the open-collector 74LS07 / SN7407 logic buffer that allows up to 30V output signal levels and has a typical or max transition delay of 20ns. 10kOhm pull-up resistors are already included on the DSP board.

Development tools:

CodeWarrior 56800/E Hybrid Controllers v7.0/v7.2 Special Edition
1) download and user code request at Metrowerks
2) IDE installer for v7.0 CW_DSP56800_R7.0.exe (303MB!)
3) licence files in DSP7.0_Lincences.zip
4) further instructions for using the user code to get an e.g. ethernet card MAC tied authorization code/licence is in the email from (1).
The licence for the 8kWord code-restricted special edition is free.

Motorola parallel port JTAG converter
1) a simple and nonexpensive DIY version that uses two 74HC244 chips can be found at www.hc08.cz (no longer available?)
2) the DSP56858 Evaluation Module Users Manual dsp56858evmum_d.pdf also has a JTAG schematic on page 46/A-8. It uses a special MC74LCX244 but a normal 74HC244 should also be able to work from 3.3V, just not as fast.

There's also a low cost Developer Starter Kit (MC56F8300DSK) that is available from Freescale for around $80. It comes with all necessary devel software, and does not require a DIY jtag adapter.


Circuit files:

versions under work, Eagle (free version from www.cadsoft.de)
schematics | PCB board | Freescale.lbr

Last design update 7.2.2005

Important notes: jtag connector pin-out needs to be updated, LM317L and 78L05 must be changed to TO-220 packaged ones because of power dissipation, and LM317T must have a 3.3V zener accross the output as the regulator seems to create voltage spikes beyond 9V at power-up (can fry the DSP)

Firmware files:

(none yet)

Lab notes: already wrote an audio-modulated 500kHz PWM testsource (used in a class-D audio amp project), where it then became apparent that even with the 56F8322 the built-in PWM module's frequency adjustment i.e. step size for freqs above 100kHz is not as fine-grained as I'd like. Step size was >4kHz, instead of a fixed sub-1kHz resolution. However at <100kHz resolution is fine.


(C) 2005 Jan Wagner