Hello,
I built the USBTinyISP and it seemed to work well. I got the driver installed on a 32bits Win 7. Green light comes on when hooked up to a usb port. I also built a Dev board for AT89S52 chips which came as a kit. I hooked up power to the dev board (6V) and connected the SPI cable to the 6 pins header on the dev board. (pin1 matching pin1). After an instant, I heard a pop and got magic smokes coming out of my USBTiny. I unplugged everything and opened the case and saw burn marks on the plastic of the case where the buffer chip is soldered.
I am not sure if anything else has been affected by my experiment but it doesn't look like as the driver still load when I connect it.
I went to a not so local electronic store and they didn't have that particular chip. Instead, they had the 74125 and the 74LS125 ones. I got one of each. Looks like the pin-out are the same. Anyone could confirm that these chips are equivalent to the 74AHC125 as stated by the staff member in the store suggested?
The dev board I am using is "DIY AT89S52 Microcontroller Development Board Set for Arduino (Works with Official Arduino Boards)" from dealextreme. There are no specs anywhere about the SPI pin-out on the board but being SPI (6 pins header), I thought it would be standard. And I did not think the power from the power supply on the board would flow to the USBTiny either. I was thinking that the power supply would feed the board and the AT89S52 as well as the power from the USB device... I read the forum section about USBTiny and saw it not being compatible but I was expecting no more than seeing a tad bit of read light flashing and simply get an unrecognized signature from the chip at worst. I thought wrong. (using AVR Studio)
So, are the 74125 and 74LS125 compatible with 74AHC125? And should I worry about other components if it gets the green light and load the driver in Win7 when hook it up?
If someone can enlighten me also about providing power to a dev board while hooking it to the USBTiny to program the chip on that board... Is it a no-no, is it supposed to be possible?
Thanks for your help.
Succesfully fried the 74AHC125 buffer chip
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- adafruit_support_rick
- Posts: 35092
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Re: Succesfully fried the 74AHC125 buffer chip
According to this post, the 74LS125 will work:
http://forums.adafruit.com/viewtopic.php?t=5555
http://forums.adafruit.com/viewtopic.php?t=5555
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- Posts: 6
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Re: Succesfully fried the 74AHC125 buffer chip
Never apply power when programming
- schmartguy1
- Posts: 22
- Joined: Tue Jan 28, 2014 3:37 pm
Re: Succesfully fried the 74AHC125 buffer chip
74125, 74LS125 and 74HC125 are functionally equivalent.
the "LS" stands for Low Power Schottky
the "HC" stands for High Current output.
simply, an "LS" is not a substitute for an "HC". they must match the circuit requirements. typically you get either higher speed (low power) or more drive but slower.
the "LS" stands for Low Power Schottky
the "HC" stands for High Current output.
simply, an "LS" is not a substitute for an "HC". they must match the circuit requirements. typically you get either higher speed (low power) or more drive but slower.
Please be positive and constructive with your questions and comments.