[time-nuts] Re: Seeking feedback on a HW Architecture for a DIY two channel timer/counter and frequency reference

[Carsten Andrich]

On 17.07.22 04:57, Lux, Jim via time-nuts wrote:
> On 7/16/22 12:44 PM, Carsten Andrich via time-nuts wrote:
>> Hi Erik,
>>
>> very interesting project. I've been using software-defined radios for 
>> 5~6 years now to evaluate our various frequency references (mostly 
>> GNSSDOs) [1]. However, the resulting measurement setups are quite 
>> expensive (>20k€ for 8 synchronous channels with USRPs X310), bulky 
>> (2HE, 500 mm depth), heavy (>10 kg), and power hungry (>100 W). I've 
>> been sporadically pondering how to design a cheap and compact, yet 
>> highly accurate alternative for about a year now. My current, 
>> unverified idea for a quad channel time interval counter is to 
>> combine 4 TDC7200 with an STM32's 32-bit timer capture (also has 4 
>> channels). The TDC should enable ~50 ps resolution.
>>
> could you gang up multiple TICCs somehow?

John Ackermann has actually done that and dubbed it the Multi-TICC [1]. 
It's not for sale and the necessary effort to assemble it is 
substantial. I'm tempted to instead spend design effort to get similar 
functionality with 4~8 channels onto a single PCB with one MCU. I think 
it's feasible, but I haven't had the time to prototype it.

Best regards,
Carsten

[1] 
https://tapr.wpengine.com/tapr-file-area/time-freq/multi-TICC_App_Note_2020-01.pdf