# BL4S200 RS232 port F crashed

**URL:** <https://forums.digi.com/t/bl4s200-rs232-port-f-crashed/24608>\
**Category:** Rabbit\
**Tags:** bl4s200\
**Created:** [March 26, 2023, 3:41pm UTC](https://forums.digi.com/t/bl4s200-rs232-port-f-crashed/24608 "2023-03-26T15:41:20Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![arizzorabbit](https://avatars.discourse-cdn.com/v4/letter/a/a87d85/32.png) [@arizzorabbit](https://forums.digi.com/u/arizzorabbit)\
**Post date:** [March 26, 2023, 3:41pm UTC](https://forums.digi.com/t/bl4s200-rs232-port-f-crashed/24608/1 "2023-03-26T15:41:20Z")

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I had a problem with the PORT F after a surtension on a lcd display.  
The port E is used so i need an other port RS232  
There is an extension for the BL4s200 for new port RS232

Thanck you for the help

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**Author:** ![TomCollins](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.digi.com/tomcollins/32/37_2.png) [@TomCollins](https://forums.digi.com/u/TomCollins)\
**Post date:** [March 29, 2023, 12:52am UTC](https://forums.digi.com/t/bl4s200-rs232-port-f-crashed/24608/2 "2023-03-29T00:52:21Z")

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The BL4S200 only has two RS232 serial ports (E and F), but looking at the [BLxS2xx schematic](https://hub.digi.com/support/products/system-on-modules/rabbitcore-sbc-bl4s-series/?path=/support/asset/schematic-blxs2xx/), it appears that you can use serial port B in SPI mode over the same lines (TXE, TXF, RXE). Doing so would interfere with using serial port E on those pins.

How did you damage serial port F? It seems odd that serial port E works when both ports use the same transceiver (U20) for I/O. Maybe you could replace U20 to restore functionality to serial port F?

Serial port C is RS485. Serial port D is (I believe) RS422 signaling (or some sort of differential SPI) running on J6 and J8.

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<div class="post-metadata">

**Author:** ![arizzorabbit](https://avatars.discourse-cdn.com/v4/letter/a/a87d85/32.png) [@arizzorabbit](https://forums.digi.com/u/arizzorabbit)\
**Post date:** [March 30, 2023, 2:22pm UTC](https://forums.digi.com/t/bl4s200-rs232-port-f-crashed/24608/3 "2023-03-30T14:22:25Z")

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Thanks for your response

I replace with this BL4S200 an BL2665 very old ( 2007)  
On this BL2665 i have problem for load the program.

On the BL4S200 i use the port E for a GSM modem and the port F for a lcd display.  
The dispay is supply at 5Vcc by a 7805 regulator.  
So the regulator crashed and the port F don’t work.

I don’t see the U20 on the card but i suspect it’s a CMS and it’s difficult to change.

So i look for the SPI mode .

Thanck you Alain Rizzo