[SOLVED] Request help understanding serial transmission of 7135 ADC

Hi,

What does the following paragraph from the ICL7135/TLC7135 datasheet entail doing, if the goal is to connect the ADC to an Armadillo (Raspberry Pi clone) please?



Attached are the Intersil and the TI datasheets for this ADC, the text content is identical in both, however the Intersil one has wiring schematics.

By serial transmission is it referring to SDI?

Would I be able to see the ANDed BUSY and CLOCK pulses on an oscilloscope, or is it not that kind of signal?

Would I need to use pigpio to attempt to implement this, or should I be able to copy, or try to put together, some Python code to read the count (and do the 10,001 subtraction)?

Does the datasheet mean that after sending the count the code will be quite complex to translate it to a useful number (e.g. 25ºC, or ... 2.65V, etc.)?

I've got the ADC on 125kHz, and checking the Broadcom datasheet for the chip on the "Pi" it looks like it can work in the MegaHertz range, so I think stuff to do with sampling rate shouldn't be an issue?

I've never done this before, so I basically have no idea what my main objectives should be, and what I need to use/study a little first (e.g. SDI or what?).

Thanks.

Obviously ICL7135 has multiplexed BCD outputs. It's designed to drive numeric displays.

Nevertheless it's possible to connect to a microcontroller by reading the BCD data and segment lines. #STROBE can be used to synchronize the data processing, RUN/HOLD to optionally start and stop the conversion.

Display oriented ADCs have been used with processors at times when there was no large offer of ADC with data interface, e.g. 30 years ago. Why do you want to use this ADC now?

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I've got the ADC on 125kHz, and checking the Broadcom datasheet for the chip on the "Pi" it looks like it can work in the MegaHertz range, so I think stuff to do with sampling rate shouldn't be an issue?

Click to expand...

Maximal guaranteed ICL7135 clock frequency is 1.2 MHz, respectively 30 conversions per second.

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Processing the BCD data with a microprocessor after latching the digit data is not very complicated, similar to converting decimal strings of fixed length to binary.

FvM said:

Display oriented ADCs have been used with processors at times when there was no large offer of ADC with data interface, e.g. 30 years ago. Why do you want to use this ADC now?

Click to expand...

Erm... retro? . I like the 71xx series, the crankhandle to get them started is a unique feature. I see that there are several ready-made projects with ADCs like the MCP3002 - which I'd much rather do as I'm interested in portable projects and reducing parts count enormously, as much as Pi things, but money's really tight this year, so I have to look at what I have in the stock cupboard of components... The 71xx series are really old but still okay for simple stuff, it was the first (and only to date) ADC I learnt to use - no code required, which helped a lot two years ago.

FvM said:

Processing the BCD data with a microprocessor after latching the digit data is not very complicated, similar to converting decimal strings of fixed length to binary.

Click to expand...

You make it sound so easy... I imagine this will be a slow process. It is SPI (both method needed and a fair place to start for a beginner), isn't it? I'll Google your last phrase to see what learning tools I can find.

Thanks very much for your help.