Speech Board for SPO256

Posted on Feb 7, 2014

This board does NOT use the CTS256AL2 text-to-speech chip. [It would seem that both SpeechChips.com and JDR still have some of these chips, though, if you're looking for some.] However, you could easily use this board to hold the SPO chip and amplifier and connect it to your own CTS circuit. All necessary pin connections do have an available solder pad for off-board connections. Additionally, there is a socket for a 12C508/9 PIC which can reduce control pin count down to 2, or even to 1. This would also allow the line-twiddling to be offloaded from the Stamp or whatever else is the master controller. I've done the bulk of the code with some debugging and fine-tuning left. Both the PIC and audio amp [LM386] are optional and there is a provision for adding either an LED on-indicator OR a separate power supply for the amp. Amp gain is 200 and seems to be adequate with 5v supply. There is some room for a trimmer cap for the crystal in case your SPO256 chip is overly sensitive to the clock stability [as one of mine is]. The board can also be fitted with a 5v voltage regulator if you can't provide it with a regulated supply. But this option is not recommended.

Speech Board for SPO256
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Speech Board for SPO256 - image 1
Click here to download the full size of the above Image.

Design goals: Small board size [hence the nested chips] Few control lines [4] Some construction options High quality circuit board Layed out with ExpressPCB s/w. [Visit Express PCB site (Manufacturing Specifications for Production Service) for more information about their product.] Double-sided, drilled, solder reflowed 4 mounting holes on corners solder mask silk screen. Pretty small [1.5" x 2.5" (ca. 3.8 cm x 6.4 cm)] and fairly densely packed the shift register is UNDER the socket for the SPO-256 bits are clocked out from LSB to MSB This board equires a moderate level of soldering proficiency and a fine soldering iron. Uses shift register to convert serial input [NOT RS232 serial] to parallel for SPO256. Only requires 4 lines to control: C - CLK for shift register [pin 0 in circuit below] I - INA for shift register [pin 1] A - ALD allophone load for SPO256 [pin 2] L - LRQ for SPO256 [pin 3]

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