August 25 2010

Didj vs LX cart diferences

looks like the pad thickness has changed from the didj to the lx

Maybe to reduce to the cost per board? Less surface area to plate?

sd pins and cart detect have longer pads now?

before this was only for the power pads

Pad size comparison, same magnification used on the microscope and angle

Category: Didj, Electronics | LEAVE A COMMENT
August 12 2010

Speech Synth Reverse Engineered

After a ton of probing and trace fallowing I have come up with this schematic :)
M14 is the piggy backed roms only one side of the pins of the chip are used
IC2 is the TM5200

Table of WTF magic

now for power im using this circuit

work fine with my arduino, now to get to coding and building an small amp for the sound out

Category: Arduino / AVR, Didj, Electronics | 4 Comments on Speech Synth Reverse Engineered
August 11 2010

TI Speech Synch Exploring

I acquired a Ti speech synthesizer module today cheep to experiment with :)
According to this old data sheet I found of the speech chip TMS5200.pdf this should be easy to interface to a Didj or arduino!
Oddly there is a second rom chip stacked on top of the original in parallel with all pins soldered to??

So I took the unit apart and removed the connector carefully to reuse it.

cleaned up the pads and lightly filed the board to fit the connector.

then carefully modified the connector so it would slide onto the board better
Next: power and bus management

1 VCC +5 Volts power supply 2 SBE Low if addr in >9000-94xx (sound port)
3 RESET* System reset (active low) 4 EXTINT* External interrupt (active low)
5 A5 Address bus, bit 5 6 A10 Address bus, bit 10
7 A4 Address bus, bit 4 8 A11 Address bus, bit 11
9 DBIN Active high = read memory 10 A3 Address bus, bit 3
11 A12 Address bus, bit 12 12 READY Active high = memory is ready
13 LOAD* Un mask able interrupt (=> BLWP @>FFFC) 14 A8 Address bus, bit 8
15 A13 Address bus, bit 13 16 A14 Address bus, bit 14
17 A7 Address bus, bit 7 18 A9 Address bus, bit 9
19 A15 Address bus, lsb. Also CRU output bit. 20 A2 Address bus, bit 2
21 GND Ground 22 CRUCLK* Inversion of TMS9900 CRUCLOCK pin
23 GND Ground 24 PHI3* Inversion of phase 3 clock
25 GND Ground 26 WE* Write Enable (derived from TMS9900 WE* pin)
27 GND Ground 28 MBE* Active low if addr in >4000-5FFF (card ROMs)
29 A6 Address bus, bit 6 30 A1 Address bus, bit 1
31 A0 Address bus, bit 0 (most significant) 32 MEMEN* Memory access enable (active low)
33 CRUIN CRU input bit to TMS9900 34 D7 Data bus, bit 7 (least significant)
35 D4 Data bus, bit 4 36 D6 Data bus, bit 6
37 D0 Data bus, bit 0 (most significant) 38 D5 Data bus, bit 5
39 D2 Data bus, bit 2 40 D1 Data bus, bit 1
41 IAQ Interrupt acknowledged by TMS9900 42 D3 Data bus, bit 3
43 VDD -5 Volts power supply 44 AUDIOIN To sound generator AUDIO IN pin
Category: Didj, Electronics | LEAVE A COMMENT
August 6 2010

DJHI hot swapping almost there and DJHI update

There was a slight bug found with the resistor used for the card detect pin for the Micro SD card hot swapping.
Originally a 300k resistor was used to pull down the SD_D3 data line.
It was found that this resistance is too high to use and will not allow for proper hot swap detection of the Mirco SD card.
Though some testing it was found that there is a 100k pull up resistor inside the LX that totally throws off the detection resistor value and makes it not work.
The Solution: Replace the 300K resistor (R4) with a 82.5k resistor.
All boards made from today on will feature this new update.

This is what the new resistor looks like
I am trying to figure out how to ship out resistors to those who already purchased a DJHI and would like to try to fix this.
There have also been reports of random shorts and strange behavior when the DJHI is plugged into a LX or Didj. I looked at the boards very closely and found a small routing problem that happens on some boards.

It is some times very very hard to see with the naked eye but under the microscope you can see some debris of the connector from the routing going a little too far. General use of the DJHI can cause this little flake of metal to flatten out and cause a short.
Solution: if you are experiencing random glitches and non power on issues, take a razor blade and CAREFULLY remove the debris from between the ends of the pads. As of today this will be checked for for every board built from now on.

Category: Didj, Electronics | 2 Comments on DJHI hot swapping almost there and DJHI update