I'm prototyping an ultrasound scanner based on AD9272 and I've got some
problems/questions. First, I would like to tell you some details about my project:
1) HV TX circuitry is not assembled yet on my PCB, it will be the next step on
prototyping. First I want to have RX channel working fine.
2) My design is as follows: 80MHz generator => AD9512 (clock distribution chip/OUT4
output used[default devided/4]) => AD9272-80 => FPGA (XC6SLX45-CSG324)
3) Only one channel of AD9272 is used now. All other 7 unused analogue LIx/LGx
inputs are tied to GND.
4) LVDS outputs from AD9272 D+/-,Frame+/-,BitCLK+/- => FPGA deserializer + post
5) TGC shape is software controlled: PC (software shape defined) => USB (FT2232H)
=> FPGA => AD7302=> AD9272 TGC input. This controll signal looks perfect on scope.
6) AD9512/AD9272 share the same SPI signals: SDIO (used only for write) and SCLK.
All the above and CSB1 (AD9512) and CSB0 (AD9272) are driven as follows: PC
(software) => USB (FT2232H) => FPGA => AD9512/AD9272.
And now some scope observations and some problems:
1a) First I want to clock the AD9272 with 80MHz, then I have to bypass the default
/4 divider on AD9512. I pull the CSB1 low (by software) and then (pseudo code):
- write(0x53,0x80) // bypass divider //
- write(0x5A,0x01) // update the changes //
This work perfect, any other SPI instructions on AD9512 work fine.
2a) And now here is the problem!!
- CSB1 high (AD9512 disabled), CSB0 low (AD9272 enabled). Scope shows it's OK.
- write(0x0D,0x09) // 1/0-bit toggle // output test mode
- write(0xFF,0x01) // update //
Doesn't work!! Scope observations:
1b) When I touch the finger to the AD9272 input, then any deserlialized bit output
(11:0) from the FPGA goes insane!!
2b) I'm not sure that my deserializer design is perfect. However, as I do the
procedure (2a), touch the finger to the AD9272 input, and observe on scope the
insane changes on any bit (1b) , it means the device is still working in its
3b) Even if my FPGA deserializer is not OK, then the analogue input finger touching
should not the FPGA outputs.
Anyway, please pay your attention at:
1c) On Power-up, touching the finger to the input makes insane changes on any bit
on the deserializer output.
2c) Upon a procedure (2a), result is (1c).
3c) Please!! Pay your attention on 3b !!
What a hell do I do wrong??