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MSP430F5529 hardware implementation - review request

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Hi,

I'm preparing the mainboard for my weather station and I almost completed the major items, especially the MSP430F5529 implementation.

 

The schematic of MSP430 connections was made basing on the LaunchPad schematics (http://www.ti.com/litv/pdf/slau533 pg. 52).

 

I am wondering if the USB part is required or not for stable microcontroller work in case I don't plan using the USB (Vusb, Vbus etc).

The .svg with my schematic is available at http://inet24.pl/~morales/schematic.svg - vector graphics, can be zoomed if needed.

 

Do I need C7 and C8? How about PUR, PU.1/DM and PU.0/DP, are they only for USB purposes and I can omit them if I do not have USB in use?

 

Thank you in advance!

 

On the schematic I missed the SBWTDIO pullup, that will be of course fixed.

 

Best Regards,

tml

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Hi,

I'm preparing the mainboard for my weather station and I almost completed the major items, especially the MSP430F5529 implementation.

 

The schematic of MSP430 connections was made basing on the LaunchPad schematics (http://www.ti.com/litv/pdf/slau533 pg. 52).

 

I am wondering if the USB part is required or not for stable microcontroller work in case I don't plan using the USB (Vusb, Vbus etc).

The .svg with my schematic is available at http://inet24.pl/~morales/schematic.svg - vector graphics, can be zoomed if needed.

 

Do I need C7 and C8? How about PUR, PU.1/DM and PU.0/DP, are they only for USB purposes and I can omit them if I do not have USB in use?

 

Thank you in advance!

 

On the schematic I missed the SBWTDIO pullup, that will be of course fixed.

 

Best Regards,

tml

 

If you are not using USB at all (also not for BSL firmware update), parts regarding USB on LP schematic can be removed. I think that there is in USB module description of slau208 info about that (USB pins termination), and I have it somewhere on paper, but not on hand right now.

 

If consumption of your module is not to high, it can be used MSP430F5529 internal LDO even USB is not used. Cap on V18 is not needed, and cap on VUSB depend if internal LDO is used or not.

 

MSP430F5529 have internal resistors for pulling on TEST/RESET pins, so there is no need for external (even you will find external 47k reset pulling on all MSP430F5xx TI schematics).

 

And yes, check all this things before making final boards.

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If you are not using USB at all (also not for BSL firmware update), parts regarding USB on LP schematic can be removed. I think that there is in USB module description of slau208 info about that (USB pins termination), and I have it somewhere on paper, but not on hand right now.

 

If consumption of your module is not to high, it can be used MSP430F5529 internal LDO even USB is not used. Cap on V18 is not needed, and cap on VUSB depend if internal LDO is used or not.

 

MSP430F5529 have internal resistors for pulling on TEST/RESET pins, so there is no need for external (even you will find external 47k reset pulling on all MSP430F5xx TI schematics).

 

And yes, check all this things before making final boards.

Thans for the response!

I have in fact found in the Fxxx family user guide (http://www.ti.com/litv/pdf/slau208m) section 1.6 Connection of Unused Pins where it'stated that in case USB is not used the following setup 

 

V18 = Open
PUR  = DVSS (A 1-M? resistor to ground is recommended)
VUSB  = Open
PU.0/DP, PU.1/DM =  Open
VBUS, VSSU =  DVSS
 
However, as for the RST pin I find the manual a bit vague:
RST/NMI = DVCC or VCC  (47-k? pullup or internal pullup selected with 10-nF (2.2 nF) pulldown - remark: The pulldown capacitor should not exceed 2.2 nF when using devices with Spy-Bi-Wire interface in Spy-Bi-Wire mode or in 4-wire JTAG mode with TI tools such as FET interfaces or GANG programmers.)
 
In fact on the LaunchPad schematic they used this 47kOhm pullup resistor with the 1nF capacitor to the ground. Assuming this 47kOhm resistor is redundant (because the RST is internally pulled-up), shall I still keep 1nF capacitor or is it not necessary as well?
 
Best Regards,
tml

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I have in fact found in the Fxxx family user guide (http://www.ti.com/litv/pdf/slau208m) section 1.6 Connection of Unused Pins where it'stated that in case USB is not used the following setup 

 

V18 = Open
PUR  = DVSS (A 1-M? resistor to ground is recommended)
VUSB  = Open
PU.0/DP, PU.1/DM =  Open
VBUS, VSSU =  DVSS

 

Yes, I was referring to this, but forgot that is outside USB module section (40).

 

However, as for the RST pin I find the manual a bit vague:

RST/NMI = DVCC or VCC  (47-k? pullup or internal pullup selected with 10-nF (2.2 nF) pulldown - remark: The pulldown capacitor should not exceed 2.2 nF when using devices with Spy-Bi-Wire interface in Spy-Bi-Wire mode or in 4-wire JTAG mode with TI tools such as FET interfaces or GANG programmers.)
 
In fact on the LaunchPad schematic they used this 47kOhm pullup resistor with the 1nF capacitor to the ground. Assuming this 47kOhm resistor is redundant (because the RST is internally pulled-up), shall I still keep 1nF capacitor or is it not necessary as well?

 

Just put 1 nF cap on reset pin, like on LP, without external pulling resistor.

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Have you read the system integration manual for the GSM radio? if not, give it a read here (pay close attention to chapter two). The GSM radio is fairly picky. 

 

Are those sensors on breakout boards? 

 

That's all i can see right now, i'll take a more detailed look later.

 

Design

I'd recommend adding a reset switch for your MSP430. You need ESD protection for the SIM card.

 

Any reason you need or want the DHT22? I really don't trust that sensor line for accurate measurements. 

 

Switch your UART line! It should look like this: 

 

_MSP430__                 _GSM RADIO_

|                  |                 |                        |

|                  | TX -> RX  |                        |

|                  | RX <- TX  |                        |

|_________|                 |____________|

 

 

 

Crystal

C2 and C3 are not needed. The UCS provides load capacitors up to 12pF.

In fact that 32Khz crystal is not really needed. The UCS has a REFO clock source that can provide a 32Khz clock signal. I'd still would leave the crystal footprint in though so that it could be added at a later time if required.

 

Power

I would recommend replacing C7 with a 100uF tantalum capacitor. That GSM radio requires a lot of power when transmitting. Also consider providing reverse current protection if you think it may happen. the GSM radio does not have any reverse current protection.

 

Follow the recommendations on reducing noise and EMI from the radio, as this could affect your analog components. The reset line seems to be really susceptible to EMI.

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Have you read the system integration manual for the GSM radio? if not, give it a read here (pay close attention to chapter two). The GSM radio is fairly picky. 

 

Are those sensors on breakout boards? 

 

That's all i can see right now, i'll take a more detailed look later.

 

Design

I'd recommend adding a reset switch for your MSP430. You need ESD protection for the SIM card.

 

Any reason you need or want the DHT22? I really don't trust that sensor line for accurate measurements. 

 

Switch your UART line! It should look like this: 

 

_MSP430__                 _GSM RADIO_

|                  |                 |                        |

|                  | TX -> RX  |                        |

|                  | RX <- TX  |                        |

|_________|                 |____________|

 

 

 

Crystal

C2 and C3 are not needed. The UCS provides load capacitors up to 12pF.

In fact that 32Khz crystal is not really needed. The UCS has a REFO clock source that can provide a 32Khz clock signal. I'd still would leave the crystal footprint in though so that it could be added at a later time if required.

 

Power

I would recommend replacing C7 with a 100uF tantalum capacitor. That GSM radio requires a lot of power when transmitting. Also consider providing reverse current protection if you think it may happen. the GSM radio does not have any reverse current protection.

 

Follow the recommendations on reducing noise and EMI from the radio, as this could affect your analog components. The reset line seems to be really susceptible to EMI.

 

Hi,

Thanks for the response!

 

> I'd recommend adding a reset switch for your MSP430. 

 
Why is it necessary? That is going to be a weather station located out of the civilized world. If the mcu hangs up then the reset button is not going to be helpful because if it hangs then the watchdog has to reset the mcu.
 
> You need ESD protection for the SIM card.
Added, thanks! (I will update the schematic in a few hours)
 
> Any reason you need or want the DHT22? I really don't trust that sensor line for accurate measurements. 
I like it, it works for me :)
 
> Switch your UART line! It should look like this: 
 
_MSP430__                 _GSM RADIO_
|                  |                 |                        |
|                  | TX -> RX  |                        |
|                  | RX <- TX  |                        |
|_________|                 |____________|
 
 
> Crystal C2 and C3 are not needed. The UCS provides load capacitors up to 12pF.
Thank you! Will remove them.
 
> In fact that 32Khz crystal is not really needed. The UCS has a REFO clock source that can provide a 32Khz clock signal. I'd still would leave the crystal footprint in though so that it could be added at a later time if required.
This device is going to be operating in winter in low temperatures like -20 or even -30 sometimes. I suppose the internally-generated frequencies are not going to be stable.
 
> Power I would recommend replacing C7 with a 100uF tantalum capacitor. That GSM radio requires a lot of power when transmitting. Also consider providing reverse current protection if you think it may happen. the GSM radio does not have any reverse current protection.
Thanks, I will replace the C7 and add a Schottky diode before the voltage regulator
 
> Follow the recommendations on reducing noise and EMI from the radio, as this could affect your analog components. The reset line seems to be really susceptible to EMI.

Here I have a problem because I cannot find a proper ferrite bead (a reference one is BLM15HD182SN1 1800ohm

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