I recently opened a SLM2008 and noticed the unpopulated header with two signal lines : looked like a RS232 header.
Browsing the web (Maxim Integrated’s website) , I found a device that could be used for the unpopulated U11 : Max3243 (exact part could be another one, as I am not sure for pins 21/22 & 23, but I only really care about the TX/RX pins). On this part, there is a RS232-to-TTL between pins 6&17 and opposite TTL-to-RS232 between 13&10.
I quickly added wires on those pins :
And the ‘bus pirate’ on the header.